text:
\section{Introduction}
Synthetic and natural nanoparticles are ubiquitous in a wide range of chemical~\cite{moshfegh2009nanoparticle},
bioanalytical~\cite{couvreur2013nanoparticles,penn2003nanoparticles},
biomedical~\cite{mitchell2021engineering,stremersch2016therapeutic,chen2016nanochemistry}
and environmental~\cite{liu2006nanoparticles} applications.
Control over nanoparticle motion is
an important aspect for many of these applications, especially for bio-analysis, drug delivery, diagnostics and
environmental monitoring
for which particle filtration, pre-concentration, directed delivery and purification
are often required~\cite{li2017progress,xie2020microfluidic,pamme2007continuous}.
Nanoparticle characterization in terms of size and surface properties -- such
as chemical composition and charge -- is also key to several nanoparticle technologies.
For example, particle size and zeta potential play a crucial role in
many biological processes, such as membrane-binding affinity,
cellular uptake and cytotoxicity~\cite{honary2013effect, miller1998,contini2018nanoparticle,contini2020size}. Size, surface charge and
surface composition  also dictate  the nanoparticles' ability to penetrate through natural barriers, such as
extracellular matrices~\cite{lenzini2020matrix,tomasetti2016influence} and the blood brain
barrier~\cite{huang2022potential}.
Consequently, control over particle size and surface properties is essential for precision drug delivery applications,
in which these properties are tuned
to increase circulation time~\cite{torchilin2005, yuan2012}, achieve high
therapeutic efficacy~\cite{ibrahim2005,gradishar2006} and reduce
toxicity~\cite{blanco2015}.
As a further example, extracellular vesicles -- i.e., lipid vescicle naturally released and internalized by cells --
has attracted much attention because of their potential as powerful therapeutic and diagnostic tools~\cite{fais2016evidence}.
Their size, surface charge and biochemical composition reflect their biogenesis
and determine the cellular uptake pathways used for intercellular communication~\cite{midekessa2020zeta}.
Thus, the characterization of the size and surface properties of these lipid vesicles is necessary to elucidate the
many physiological and pathological processes they are involved with~\cite{yanez2015biological}, and
to exploit their potential as drug carrier and disease biomarkers.

In the last two decades, there has been a growing interest in microfluidic
strategies for both particle manipulation~\cite{zhang2020concise,sajeesh2014particle} and
characterization~\cite{gholizadeh2017microfluidic,yang2018review}.
This is due to the
many advantages offered by microfluidic technologies compared to
their conventional counterparts, including cost-effectiveness, reduced consumption
of samples and reagents, high precision, portability and capability to perform
multiplexed analysis and continuous flow processing~\cite{samiei2016, sackmann2014, rodriguez2021}.
In this context, diffusiophoresis -- namely, the phoretic transport of colloidal particles
induced by a solute concentration gradient -- has emerged as a valuable
tool for particle manipulation and characterization in microfluidic chips~\cite{shin2020diffusiophoretic,shim2022diffusiophoresis},
and many devices have been proposed to exploit it for
targeted delivery~\cite{shin2016size,tan2021two}, focusing~\cite{Abecassis2008d}, trapping~\cite{singh2020reversible,singh2022enhanced},
accumulation~\cite{shin2017accumulation}, sorting, filtration
and separation~\cite{shimokusu2019colloid,shin2017co,ault2018diffusiophoresis,ha2019dynamic,seo2020continuous}.
Furthermore, since the diffusiophoresis mobility of colloids can depend on particle
size~\cite{shin2016size,rasmussen2020size, shimokusu2019colloid} and surface charge
\cite{prieve1984motion, velegol2016origins, shin2017low}, this transport mechanism
has been exploited also to detect and characterize these particle properties.
A low-cost zeta potentiometry microchip was developed by relying on
the fluid and particle motion induced within dead-end microchannels
via transient salt concentration gradients~\cite{shin2017low}.
This microfluidic device has a simple geometry, and it is cheap and easy to fabricate.
However, it allows only for batch (i.e. non-continuous) measurements,
due to the transient nature of the salt concentration gradient and the
need for regular flushing of the dead-end pores to replace the sample and prevent clogging.

Imposing a salt concentration gradient in a microchip also results in a diffusioosmotic
slip velocity at the charged walls of the fluidic
channels~\cite{anderson1989colloid,marbach2019osmosis}.  Such a slip velocity
is typically weak and has usually negligible effects in pressure-driven flows
within open micron-sized channels. Conversely, diffusioosmotic effects can
become significant in dead-end channels~\cite{kar2015enhanced,shin2016size} or
in highly confined flows within nanotubes~\cite{siria2013giant} and
nanochannels~\cite{lee2014osmotic}.  Recently, diffusiophoresis and
diffusioosmosis have been jointly exploited in a cleverly designed microfluidic platform
for the separation and characterization of liposomes and extracellular
vesicles~\cite{rasmussen2020size}.  In this device, a shallow tapered
open-ended nanochannel is exposed to a steady salt concentration gradient and
this leads to the size- and charge-dependent accumulation of lipid vesicles
nearby the region where the diffusioosmotic flow velocity and the particle
diffusiophoretic velocity balance each other.  This microfluidic system enables
the pre-concentration of lipid vesicles as well as the accurate measurements of their
diameter and zeta potential. Although this is the first significant exploitation of diffusioosmotic flows
for particle characterization, the sample analysis is again performed in batches, with a small fraction
of the sample injected into the device being analyzed at any given time.
Moreover, the use of nanochannels makes the device fabrication process
more complex and expensive, because it requires costly clean-room fabrication procedures such as
reactive ion etching techniques~\cite{lee2014osmotic,marbach2019osmosis,rasmussen2020size}.
Nanochannel devices are also more vulnerable to obstruction and clogging,
compared to microchannel chips.

To address these limitations, we propose a novel microfluidic strategy for the manipulation
and characterization of colloidal particles via solute concentration gradients
in continuous flow, low-cost and easy to fabricate microfluidic devices.
First, we report and investigate a newly observed particle focusing mechanism occurring in a single $\Psi$-junction microchannel device.
The intertwined effects of particle diffusiophoresis and flow
diffusioosmosis, induced by steady salt concentration gradients,
enable the accumulation of colloidal beads and liposomes at multiple focusing regions
nearby the charged walls of the microchannels.
Notably, unlike previous studies, here
the diffusiophoresis and diffusioosmosis effects do not compete one against the other by pushing
particles along parallel and opposite directions, but, instead, they
act synergistically by moving particles along two perpendicular directions.
This allows for the first time the continuous and high-throughput manipulation of colloids in
an open-ended micron-sized channel via diffusioosmotic flows
without recurring to dead-end or nano-sized channel geometries, therefore reducing the risk
of device clogging and avoiding the need of expensive device fabrication procedures.
To exploit this novel mechanism, we introduce a new double-junction device that can be
used for the continuous separation and characterization of
nanoparticles based on their size or zeta potential.
Furthermore, we investigate how the chemical composition
and lipid phase of the membrane affect the liposome diffusiophoretic response
and establish a relationship between the latter and the charged lipid content of the membrane.

\section{RESULTS AND DISCUSSIONS}

\subsection{Particle focusing in single junction devices}

A $\Psi$-junction microfluidic device was used to generate a steady-state
gradient of salt concentration (referred to as $c$ in the following) by pumping
a low concentration ($c_{\scriptscriptstyle L} = 0.1~$mM) LiCl aqueous solution in the inner channel
and a high concentration ($c_{\scriptscriptstyle H} = 10~$mM) LiCl aqueous solution in the outer
channels (Fig.\,\ref{fig:Fig1}a). Outer and inner streams had a constant flow
rates of $3.65~\upmu$L/min.
A similar flow configuration was adopted in previous
studies~\cite{singh2022enhanced,
singh2020reversible,singh2022composite,Abecassis2008d,Abecassis2009b} to
investigate the dynamics of charged colloids under steady-state salt gradients
and continuous flow conditions.

In a first set of experiments, carboxylate polystyrene nanoparticles (NPs),
$216.5\pm 0.9~$nm in diameter (Invitrogen, USA) and $\zeta=-54.9\pm0.7$~mV, were dispersed in the inner flow only,
thus leading to the formation of a fluorescent stream of colloidal solution –
hereby referred to as colloidal band – within the central region of the
channel. The boundaries of the colloidal band are represented by the black
dotted lines in the 3D schematic of the device in Fig.\,\ref{fig:Fig1}a.
A $x,y,z$-axis reference system is introduced as shown in the figure. The origin of $z$-axis is
located at the junction, whereas the origins of the $x$ and $y$ axis are located at the mid-points
along the channel width and depth, respectively.
The parallel streams of electrolyte solutions at different salt concentrations
generated a salinity gradient in the direction transverse to the flow (red
arrows parallel to $x$-direction in Fig.\,\ref{fig:Fig1}a), which caused the broadening of the colloidal
band due to the diffusiophoresis migration of  charged nanoparticles towards
higher salt concentration regions.  In agreement with previous
studies~\cite{Abecassis2008d,Abecassis2009b} , the particle transverse profiles
showed an enhanced diffusive dynamics in the transverse direction and the
colloidal band width, $\Delta w$, increased linearly with the square root of
the longitudinal distance $z$ from the junction (inset in
Fig.\,\ref{fig:Fig1}c). As discussed by Abecassis and co-workers, the enhanced
colloid diffusivity in the transverse direction is caused by the coupling of
the diffusiophoretic migration of particles with the underlying salt diffusion
process~\cite{Abecassis2008d} .

\begin{figure}[t!] \begin{center}
\includegraphics[width=0.88\columnwidth]{Fig1.pdf}
\end{center}
\caption{
\footnotesize
(a)
3D schematic and micrographs of the single $\Psi$-junction device.
The LiCl solution at high concentration ($c_{\scriptscriptstyle H}$) was injected in the
outer channels, whilst the inner channel contained the low
concentration ($c_{\scriptscriptstyle L}$) LiCl solution seeded with fluorescent ($d$ = $216.5\pm 0.9~$nm) carboxylate polystyrene nanoparticles (NPs). The
3D location of accumulated NPs (green dots) is shown
together with the directions of diffusiophoresis migration (red arrows) and diffusioosmosis
flow (blue arrows). The decay of the distance $\Delta_{\mbox{\tiny{DO}}}$ between the accumulation peaks with the
distance from the junction ($z$) is visible in the top view epi-fluorescence images (blue
rectangle). The four accumulation regions in the  $(x,y)$-plane are visible in
the confocal image of the channel cross-section at a distance $z/w_i=25$ from the junction (front view, red
rectangle). (b) Experimental intensity profiles along the transverse
$x$-direction with a salt gradient (solid lines) and
without a salt gradient (dashed lines), at increasing distances $z/w_i$.
(c) Experimental and numerical peak separation distance $\Delta_{\mbox{\tiny{DO}}}$ as a function of the
distance $z/w_i$.
Inset shows the profile of the colloidal band width, $\Delta w$, as a function of the distance $z/w_i$.
(d) NP concentration profiles along the transverse $x$-direction at increasing
distances $z/w_i$, predicted by numerical simulations.
(e) Numerical map of the channel cross-section at a distance $z/w_i=25$
showing the NP concentration field, the salt concentration isolines and the total particle
velocity field, $\mbox{\boldmath$u$}_{\mbox{\tiny{p}}}=\mbox{$\bm u$}+{\mbox{\boldmath$u$}}_{\mbox{\tiny{DP}}}$, streamlines (white arrows)
with diffusioosmotic slip velocity, ${\mbox{\boldmath$u$}}_{\mbox{\tiny{DO}}}$, at the channel walls.
\label{fig:Fig1}}
\end{figure}

The chemical gradient field also prompted the appearance of two
distinct peaks of focused nanoparticles (when looking at the channel from above), as showed
by the epi-fluorescence images in the blue rectangle of Fig.\,\ref{fig:Fig1}a.
The peaks were separated from each other by a distance $\Delta_{\mbox{\tiny{DO}}}$, initially equal to the inner channel
width $w_i$. The value of $\Delta_{\mbox{\tiny{DO}}}$ rapidly decreased with $z$ over a typical distance $d\simeq 23\,w_i$
and eventually plateaued at a constant \emph{saturation} value (Fig.\,\ref{fig:Fig1}c).
The decay distance $d$ was estimated by
intersecting two straight lines fitting the $\Delta_{\mbox{\tiny{DO}}}$ versus $z$ plot for $z/w_i \rightarrow 0$ and $ z/w_i \rightarrow 45$, respectively.
Particle peaks did not form when no salt concentration gradient was imposed (Fig.\,S1b,c).
The particle focusing effect is quantified by plotting the fluorescence intensity profile
against the transverse $x$-direction (perpendicular to the direction of the flow) at different
distances, $z/w_i$, downstream the junction (Fig.\,\ref{fig:Fig1}b).
Note that epi-fluorescence micrographs are generated from the convolution of the particle fluorescence intensity
with the microscope point-spread function~\cite{gu2000advanced} . Thus, the intensity profiles of Fig.\,\ref{fig:Fig1}b
are the result of an integration of the particle fluorescence intensity
over an optical window, whose characteristic size in the vertical $y$-direction
is given by the depth of field of the optical system (ca. $10\,\upmu$m).
The fluorescence intensity profiles are normalized with respect to the intensity of
the colloidal solution with particle concentration, $n_0$, injected in the inner channel of the device.
From the profiles in Fig.\,\ref{fig:Fig1}b,  we can observe a clear effect of focusing of the nanoparticles (solid lines)
when compared to the case without salinity
gradient (dashed lines). A confocal scan of the $(x,y)$-plane confirms that under salinity
gradient conditions, charged particles were accumulating at the top and bottom
of the device walls in four symmetrical positions (red rectangle in Fig.\ref{fig:Fig1}a).
In the absence of a salinity gradient, the particle distribution profile in the same plane was uniform (Fig.\,S1c), therefore
the observed particle dynamics was  driven by the salt contrast generated in the microchannel.

\begin{figure}[t!]
\begin{center}
\includegraphics[width=\columnwidth]{Fig2.pdf}
\end{center}
\caption{Relationship between the direction of the salt gradient and the
dynamics of the peak displacement  mechanism due to diffusioosmosis. (a,b) Schematic
diagrams of a single $\Psi$-junction microchip, where carboxylated NPs are
uniformly injected (in all channels) with two different configurations of salt
gradient. In (a), high concentration salt is in the outer channels ($c_{\scriptscriptstyle H}/c_{\sst L}$ = 100), whilst in (b) high salt concentration salt is in the inner channel.
Red-to-white shade qualitatively indicates the field of salt concentration.
Red (blue) arrows show the direction of diffusiophoresis transport (diffusioosmosis flow).
(c,d) Normalized fluorescent intensity profile plots along the transverse direction
at various distances $z/w_i$ downstream the junction, for the configurations depicted in
schematics (a) and (b), respectively. (g,h) Normalized longitudinal distance $\Delta_{\mbox{\tiny{DO}}}$ plotted
with respect to the normalized distance $z/w_i$ for the
configurations (a) and (b), respectively.  \label{fig:DO_exp}} \end{figure}

The formation of peaks at the channel walls are in agreement with the observations reported in our previous study,
where we investigated the diffusiophoresis manipulation of charged nanoparticles in a $\Psi$-junction channel fitted with a microgrooved substrate~\cite{singh2020reversible} .
Our analysis revealed that the particle accumulation regions at the flat wall of the device were induced
by the vertical component of the salt concentration gradient which is originated by the Poiseuille-like velocity profile
in the rectangular microchannel~\cite{singh2020reversible} .
Conversely, the convergence of the peaks in the $(z,x)$-plane towards lower
salinity regions is unprecedented. This particle behavior is also entirely unexpected as it seems to contradict the well-established interpretation
of particle diffusiophoresis~\cite{anderson1989colloid} , according to which colloids migrate towards higher
salinity regions with a diffusiophoresis velocity ${\mbox{\boldmath$u$}}_{\mbox{\tiny{DP}}} = \Gamma_{\mbox{\tiny DP}} \mbox{$\bm \nabla$} ( \ln c)$
when the diffusiophoresis mobility $\Gamma_{\mbox{\tiny DP}}$ is positive – as it is the case for negatively charged particles
in LiCl solutions~\cite{Abecassis2008d} .
This implies that additional phenomena, such as
hydrodynamics and diffusioosmosis induced flows, must be involved in the
mechanism responsible for the transverse deviation of the peaks.

To verify our hypothesis, two additional experiments with different
flow configurations were conducted (Fig.\,\ref{fig:DO_exp}a,b). First, a salinity gradient
was imposed as done in the experiment depicted above (high salt concentration
$c_{\scriptscriptstyle H}$ in the outer channels and low concentration $c_{\scriptscriptstyle L}$ in the inner channel).
However, contrary to what was done in the initial experiment, a homogeneous
solution of nanoparticles was injected in both inner and outer channels
(Fig.\,\ref{fig:DO_exp}a). In a second configuration, the chemical gradient was
swapped (high salt concentration in the inner channel,
Fig.\,\ref{fig:DO_exp}b). As showed by the fluorescence intensity
profiles along the transverse direction (Fig.\,\ref{fig:DO_exp}c,d),
the focused peaks induced by diffusiophoresis effects
were observed to converge ($\Delta_{\mbox{\tiny{DO}}}$ decreases with the distance) in the
first configuration (Fig.\,\ref{fig:DO_exp}a) and diverge
($\Delta_{\mbox{\tiny{DO}}}$ increases with the distance) in the second configuration
(Fig.\ref{fig:DO_exp}b). As
observed in the previous experiment, the variation of $\Delta_{\mbox{\tiny{DO}}}$ with $z$ (Fig.\,\ref{fig:DO_exp}d,e)
was rapid at shorter distances
from the junction ($z/w_i\lesssim25$) and more slowly at larger distances ($z/w_i\gtrsim25$).
By swapping the salinity gradient, we effectively interchanged the chemically
generated electrical field that gave birth to the fluid flow near the charged walls
induced by the diffusioosmosis slip velocity, ${\mbox{\boldmath$u$}}_{\mbox{\tiny{DO}}} = - \Gamma_{\mbox{\tiny DO}} \mbox{$\bm \nabla$} ( \ln c)$,
where the diffusioosmosis coefficient, $\Gamma_{\mbox{\tiny DO}}$, has same sign and order of
magnitude of $\Gamma_{\mbox{\tiny DP}}$.
No physical parameters or properties in
our system were varied otherwise.
Consequently, the systematic counter-intuitive transversal behavior of focused peaks in both
configurations (Figs.\,\ref{fig:DO_exp}d,e) suggests that they were deeply
affected by diffusioosmosis flows – which also justifies our choice of notation, $\Delta_{\mbox{\tiny{DO}}}$, for the peak distance.
In other words, the peak displacement was always against the
diffusiophoresis-driven motion predicted for $\Gamma_{\mbox{\tiny DP}} > 0$ (blue arrows in Fig.\ref{fig:DO_exp}a,b),
and, instead, it had always the same direction of the diffusioosmosis slip velocity
for $\Gamma_{\mbox{\tiny DO}}>0$ (red arrows in Fig.\ref{fig:DO_exp}a,b).
Note that in these two complementary experiments the presence of particles in both
inner and outer streams resulted in the formation of two additional, but narrower and more intense peaks,
separated from each other by a distance $\Delta_{\mbox{\tiny{DP}}}$ (Fig.\,\ref{fig:DO_exp}c,d)
which evolved in an opposite way compared to $\Delta_{\mbox{\tiny{DO}}}$ (insets in Fig.\,\ref{fig:DO_exp}e,f).
These peaks had been previously reported~\cite{Abecassis2009b} and are intrinsically different from
the ones discussed so far. Indeed, they form as the transverse $x$-component of the chemical gradient induces a
particle migration towards higher salt regions \emph{via} diffusiophoresis
only -- thus the notation $\Delta_{\mbox{\tiny{DP}}}$. This causes nanoparticles to accumulate along the entire depth of the channel and not just
nearby the channel walls~\cite{Abecassis2009b} .
In addition, the transversal migration of these peaks is extremely slow as their separation
distance $\Delta_{\mbox{\tiny{DP}}}$ is proportional to $z^{1/2}$, which is notably the
same scaling as $\Delta w$.
Conversely, the separation distance $\Delta_{\mbox{\tiny{DO}}}$ changes much faster with the
distance from the junction (Fig.\,\ref{fig:DO_exp}e,f).

A numerical analysis was performed in COMSOL Multiphysics to confirm our
interpretation of the experimental observations.  The numerical hydrodynamic
velocity field $\mbox{$\bm u$}$, salt concentration $c$, and particle concentration $n$,
were calculated in a 3D domain consisting of a straight rectangular channel.  A
slip velocity  ${\mbox{\boldmath$u$}}_{\mbox{\tiny{DO}}} = - \Gamma_{\mbox{\tiny DO}} \mbox{$\bm \nabla$} ( \ln c)$ was imposed at the channel
walls and the particle velocity $\mbox{\boldmath$u$}_{\mbox{\tiny{p}}}$ was calculated as the sum of the hydrodynamic
velocity and the diffusiophoresis velocity, $\mbox{\boldmath$u$}_{\mbox{\tiny{p}}}=\mbox{$\bm u$}+{\mbox{\boldmath$u$}}_{\mbox{\tiny{DP}}}$.
The value of $\Gamma_{\mbox{\tiny DO}}$ for the channel walls could not be measured, so it was used
as an adjusting parameter in the model to achieve a good match between experimental and numerical
results (see Numerical Methods section for details).
The simulated transverse profiles of the normalized particle concentration $n/n_0$,
at increasing distances $z$ downstream the junction,
are shown in~Fig.\,\ref{fig:Fig1}d, and they are in good agreement with the fluorescence intensity
profiles measured in the experiments (Fig.\,\ref{fig:Fig1}b). It is worth noting that a close quantitative match
is not expected since the experimental profiles corresponds to the convolution
of the particle fluorescence intensity with the microscope point-spread function~\cite{gu2000advanced} ,
whereas the numerical profiles are directly obtained from the simulated particle concentration field.
A good quantitative agreement between experiments and simulations can be seen for the peak separation
$\Delta_{\mbox{\tiny{DO}}}$ at increasing distances from the junction (Fig.\,\ref{fig:Fig1}c), which is consistent
with the fact that the effect of the microscope point-spread function on $\Delta_{\mbox{\tiny{DO}}}$ measurements should be negligible.
Fig.\,\ref{fig:Fig1}e shows the simulated particle concentration field on the plane perpendicular to
the flow direction at $z/w_i=25$, and this is in a good agreement with the confocal image of the channel
cross-section at the same distance from the junction (Fig.\,\ref{fig:Fig1}a).
As expected, the salt concentration isolines in Fig.\,\ref{fig:Fig1}e are bent towards the outer flow
because of the Poiseuille-like hydrodynamic velocity profile. Consequently, the onset of a vertical
component of the salt concentration gradient and, thus, of the diffusiophoresis velocity, causes the accumulation
of particles at the top and bottom walls.
The diffusioosmosis slip velocity at the walls induces the formation of four symmetric recirculation regions
in the in-plane total particle velocity field $\mbox{\boldmath$u$}_{\mbox{\tiny{p}}}$, whose streamlines are showed by white arrows in Fig.\,\ref{fig:Fig1}e.
Consequently, the accumulated particles are advected toward the central region of the channel, namely from higher to lower
salt concentration regions. To summarize, the observed particle behavior is governed by
a combination of particle diffusiophoresis along the vertical axis, which induces particle accumulation,
and diffusioosmosis flow along the horizontal axis, which pushes the accumulation peak towards the center of the channel.

\subsection{Particle size detection and size-based separation in double-junction devices}

The $\Psi$-junction microchip, depicted in Fig.\,\ref{fig:Fig1}a,
could be potentially adopted for the online pre-concentration, via
solute-driven transport, of charged synthetic or biological colloids,
including macromolecules~\cite{lechlitner2018macromolecule} ,
liposomes~\cite{shin2016size} , exosomes~\cite{rasmussen2020size} ,
viruses~\cite{Palacci2010b} and bacterial cells~\cite{shim2021co} . This can be
particularly useful for applications such as microfluidic point-of-care
diagnostics and point-of-need bioanalytical testing, provided that the target
analytes are charged and, thus, susceptible to diffusiophoresis migration.
Alternatively, the same device could be used for the solute-driven
accumulation of charged nanoparticles that are conjugated to recognition moieties, such as
antibodies or aptamers, for the capture and detection of the target molecules~\cite{azzazy2009vitro} .
Furthermore, since the diffusiophoresis mobility depends on both particle
size and zeta potential~\cite{prieve1984motion,shin2016size} , the
diffusiophoresis-driven accumulation of nanoparticles at the device walls could be
exploited also for particle characterization, fractioning (commonly known as field flow fractioning) and sorting.
However, the device configuration
showed in Fig.\,\ref{fig:Fig1}, does not lend itself to such
applications, because the accumulation peaks are advected towards the central region of the channel, thus
overlapping with the bulk colloidal stream. Consequently, particle fractioning and
sorting are not possible. Moreover, the fluorescence intensity
of the accumulation peaks is partially screened by the background fluorescence signal
generated from the colloids in the bulk (see Fig.\ref{fig:Fig1}a,b), thus limiting the accuracy of the peak intensity detection and
hampering the ability to characterize particles by charge or size.
These limitations could be overcome if the accumulation peaks migrated away from the bulk colloidal stream.
To achieve this, first we tested a different flow configuration, whereby a salinity gradient was imposed
as done in the experiment of Fig.\,\ref{fig:Fig1} –- namely higher salt concentration $c_{\scriptscriptstyle H}$ in
the outer channels and lower salt concentration $c_{\scriptscriptstyle L}$ in the inner channel -- but the
colloidal particles were present in the outer stream only. However, this test came
to no avail (see Fig.\,S2 in Support Information Material), since the accumulation peaks did not form.
This is because  the salt concentration isolines, shown in Fig.\,\ref{fig:Fig1}e, are bent outwards
only within the inner stream region of the channel ($|x|/w_i\le0.5$), but
no colloids are now present in that region. As a result, the vertical component of the salt gradient
no longer leads to the formation of particle accumulation peaks.
Therefore, a new chip design was required to exploit the observed phenomenon of
particle focusing for particle fractioning, separation and characterization.
Fig.\,\ref{fig:2JD}a,b depict the blueprint of the double $\Psi$-junction microchip designed for this purpose.
The channel geometry is similar to the one of the previous device, but
a second $\Psi-$junction was added upstream of the first junction.
The downstream junction is used to regulate the salt concentration gradient in the device by swapping
the outer flow stream between a low salt concentration ($c_{\scriptscriptstyle L}$) solution, leading to no salt gradient (Fig.\,\ref{fig:2JD}a),
and a high salt concentration ($c_{\scriptscriptstyle H}$) solution, generating a steady-state salt gradient (Fig.\,\ref{fig:2JD}b).
The upstream junction allows to control the position of the colloidal stream within the main channel.
All streams injected from the inlet channels of the upstream junction have a low salt concentration ($c_{\scriptscriptstyle L}$), but only
the outer streams are laden with colloidal particles. Consequently, the inner region of the channel
remains particle-free so that, upon imposition of the salt gradient, the focused particle peaks
can converge into this region without overlapping with the bulk colloidal stream.

\begin{figure}[H]
\begin{center}
\includegraphics[width=\columnwidth]{Fig3.pdf}
\end{center}
\caption{Particle focusing and fractioning in a two $\Psi$ junction device.
(a,b) schematic diagrams of a two $\Psi$ junction microchip and their
respective fluorescent images of PS-COOH NPs ($\textit{d}$ = 549.8 $\pm$6.8 nm, $\zeta$=
-50.4 $\pm$0.2 mV) at various distances from the junction when there is no salinity
gradient ($\nabla$\textit{c} = 0) in (a) and when there is a salinity gradient
($c_{H}$/$c_{L}$=100) shown in (b). Scale bar is 75 $\upmu$m. (c) Normalized
fluorescent intensity profiles when there is no salinity gradient (blue
curve) and  when there is a salinity gradient (red curve) at various distance
downstream the junction \label{fig:2JD}} \end{figure}

This new double-junction device was first tested using carboxylate
polystyrene nanoparticles ($\textit{d}$ = 549.8 $\pm$6.8 nm, $\zeta$=
-50.4 $\pm$0.2 mV). Epifluorescence micrographs were taken at different
distances downstream the junction, $z/w_m$, either in absence or presence of a
salt concentration gradient (Fig.\,\ref{fig:2JD}a,b).  Note that for the
double-junction device, the width of the inner channel of the downstream
junction, $w_m=250\,\upmu$m, is used as the characteristic channel size and
all lengths are normalized with respect to it.  The corresponding fluorescent
intensity profiles along the transverse direction $x$ show that peak formation
occurred when a salinity gradient was imposed (red curves in
Fig.\,\ref{fig:2JD}c). Crucially, the peaks moved toward the inner region of
the channel, which would otherwise be empty in the absence of a salt
concentration gradient (blue curves Fig.\,\ref{fig:2JD}c).
\begin{figure}[H]
\begin{center}
\includegraphics[width=\columnwidth]{Fig4.pdf}
\end{center}
\caption{Focusing parameter in double-junction device for carboxylate polystyrene nanoparticles
($\textit{d}$ = 549.8 $\pm$6.8 nm, $\zeta$=
-50.4 $\pm$0.2 mV)
(a) Normalized fluorescent
intensity profile at $z/w_m=36$
without salinity gradient (blue curve) and with salinity gradient
(red curve). The region of interest corresponds to a selected central
region of the channel, $x/w_m\in[-0.2,0.2]$. The focusing parameter, $\bar{I}$, is calculated as the
average fluorescence intensity over the region of interest. (b) Focusing parameter
at different distances downstream the junction ($z/w_m$) under no salinity gradients (solid circles) and
with a salinity gradient (empty circles). The blue and red dashed lines are the
focusing parameter values corresponding to their respective intensity plots in
(a) at $z/w_m$ = 36.  \label{fig:f_param}} \end{figure}
To quantify this focusing effect, we introduce the focusing parameter,
$\bar{I}$, defined as the average value of the fluorescent intensity profile
within the range of interest, $x/w_m \in [-0.2,0.2]$, which is equivalent
to a transverse section, ca. $50\,\upmu$m wide, located at the center of the channel (Fig.\,\ref{fig:f_param}a).
Note that the width of the region of interest is chosen to exclude the
fluorescence intensity generated by the particles in the bulk colloidal stream, namely the gray shaded
regions in Fig.\,\ref{fig:f_param}a.
Fig.\,\ref{fig:f_param}b shows the focusing parameter at increasing distances $z/w_m$
downstream the junction in the presence (empty circles) and absence (solid circles) of a
salt concentration gradient. Under the examined conditions,
at $z/w_m=36$,
the focusing parameters were $\bar{I}_{\scriptscriptstyle H}=0.66$ and $\bar{I}_{\scriptscriptstyle L}=0.03$
with and without a salt concentration gradient, respectively.

Since the formation of the accumulation peaks is driven by the diffusiophoresis
migration of charged nanoparticles from the channel bulk toward the walls, it
is reasonable to expect that the peak intensity, and thus the focusing
parameter, can be correlated to the diffusiophoresis coefficient of the
nanoparticles.  For a charged nanoparticle in an electrolyte solution, the
diffusiophoresis coefficient $\Gamma_{\mbox{\tiny DP}}$ is an increasing function of the
particle size~\cite{prieve1984motion,shin2016size}, if the thickness of the
Debye layer $\kappa^{-1}$ formed around the particle is a few percent greater
than the particles radius $a$, namely $(\kappa a)^{-1}\gtrsim 1\%$. On the
other hand, for $(\kappa a)^{-1}\rightarrow 0$ the coefficient, $\Gamma_{\mbox{\tiny DP}}$,
levels off to a constant value that is independent of the particle size.  In a
0.1~mM LiCl solution, the Debye layer thickness is $\kappa^{-1}=32\,$nm,
therefore, it is expected that for sub-micron particles ($2a\lesssim
1\,\upmu$m), the coefficient $\Gamma_{\mbox{\tiny DP}}$ and the accumulation peak intensity
increase with the particle size.  To verify this hypothesis, we measured the
focusing parameter for carboxylate polystyrene particles with a diameter
ranging from tens nanometers to one micrometer. Note that the zeta potential of the
particles was very similar for all diameters (Tab.\ref{tab:I_d}).  From the
logarithmic plot in Fig.\,\ref{fig:size}a, it is apparent that the focusing
parameter $\bar{I}$ increases with the particle diameter, $d_{\scriptscriptstyle DLS}$, determined
via dynamic light scattering (DLS).  Interestingly, $\log \bar{I}$ and $\log
d_{\scriptscriptstyle DLS}$  are linearly correlated  ($R^2=0.99$).
\begin{equation} \log \bar{I} = 0.299\, \log d_{\scriptscriptstyle DLS} -0.941 \label{eq:I_d}
\end{equation}
where the value of $d_{\scriptscriptstyle DLS}$ is expressed in nanometers.  Consequently,
Eq.\eqref{eq:I_d}  can be effectively used as a calibration line for the
microfluidic characterization of the size of nanoparticles of similar zeta potential, whereby the focusing
parameter $\bar{I}$ is measured experimentally  to determine the nanoparticle
diameter
 \begin{equation} d_{\scriptscriptstyle MF} = \left({8.73}~{\bar{I}}
\right)^{3.34} \label{eq:d_I} \end{equation}
with the value of the microfluidically measured diameter, $d_{\scriptscriptstyle MF}$, expressed in nanometers.  The uncertainty
$\sigma_d$ on $d_{\scriptscriptstyle MF}$ can be calculated from the experimental uncertainty
$\sigma_I$ on $\bar{I}$ via error propagation in Eq.\eqref{eq:d_I},
which leads to $\sigma_d^2 = 11.18\, d_{\scriptscriptstyle MF}^2 \sigma_I^2/\bar{I}^2$.
Tab.\,\ref{tab:I_d} shows a comparison between the particle diameter, $d_{\scriptscriptstyle DLS}$,
measured via DLS, and the particle diameter, $d_{\scriptscriptstyle MF}$, measured via the proposed
microfluidic method.  From the absolute relative difference between the DLS and
microfluidic measurements, $\varepsilon_r=|d_{\scriptscriptstyle DLS}-d_{\scriptscriptstyle MF}|/d_{\scriptscriptstyle DLS}$, it can be
concluded that our microfluidic device can be successfully used to measure the
diameter of sub-micron particles within a reasonable accuracy.

\begin{figure}[t!]
\begin{center}
\resizebox{6.5in}{!}{\input{Fig5.pdf_tex}}
\end{center}
\caption{Particle size characterization and particle separation. (a)
Average focusing parameter for different particle sizes at approximately the
same zeta potential (see Tab.\,\ref{tab:I_d}).
(b-c) Epi-fluorescence images taken at
$z/w_m$ = 36 showing particle dynamics of mixed yellow green fluorescent
(505/515) 36 nm  and red fluorescent (580/605) 1098 nm carboxylate polystyrene colloids under
no salinity gradient (b) and with  salinity gradient (c). Scale bar is
$50\,\upmu$m. White dashed line corresponds to
the microfluidic channel boundaries. \label{fig:size}} \end{figure}

\begin{table*}[t!]
\caption{
Comparison between dynamic light scattering (DLS) and microfluidic (MF) characterization
of sub-micron particle size. $\bar{I}$ measured focusing parameter, $d_{\scriptscriptstyle DLS}$ particle size
determined via DLS, $\zeta$ particle zeta potential, $d_{\scriptscriptstyle MF}$ particle size
determined microfluidically via Eq.\eqref{eq:d_I}, $\varepsilon_r$ absolute relative difference
between $d_{\scriptscriptstyle DLS}$ and $d_{\scriptscriptstyle MF}$. The error for $d_{\scriptscriptstyle DLS}$ and $\zeta$ represent the standard deviation obtained from the instrument. The error for $\bar{I}$ is the standard error from experimental mean values.}

\begin{center} \begin{tabular}{C{0.15\textwidth}
C{0.15\textwidth} C{0.15\textwidth} C{0.15\textwidth} C{0.15\textwidth} }
\toprule \textbf{$\bar{I}$} &
\textbf{$d_{\scriptscriptstyle DLS}$} (nm) & $\zeta$ (mV)  & \textbf{$d_{\scriptscriptstyle MF}$} (nm) & $\varepsilon_r$ \\
\hline
0.323 $\pm$ 0.03 & 36 $\pm$ 0.2 & -58.3 $\pm$ 1.4 &32 $\pm$ 9 & 12\%   \\
0.511 $\pm$ 0.01  & 117 $\pm$ 0.5 & -57.6 $\pm$ 1.2   &150 $\pm$ 13  & 28\%   \\
0.561 $\pm$ 0.02  & 217 $\pm$ 0.9  & -54.9 $\pm$ 0.7   &206 $\pm$ 23 & 5\%   \\
0.735 $\pm$ 0.03  & 550 $\pm$ 6.8 & -50.4 $\pm$ 0.2    &505 $\pm$ 57 & 8\%   \\
0.929 $\pm$ 0.02 & 1098 $\pm$ 29 & -55.5 $\pm$ 0.7   &1108 $\pm$ {70} & 1\%   \\
\bottomrule \end{tabular} \end{center}
\label{tab:I_d} \end{table*}

The combined effects of peak formation and drift towards the center of the channel can be exploited also for
particle size-based separation.
To demonstrate this additional application of the double-junction chip,
a binary colloidal mixture of 36~nm and $1.098\,\upmu$m diameter particles was injected into the device.
The carboxylate polystyrene particles were stained with fluorophores with different
emission peaks, namely
515~nm (yellow-green) for the smaller particles and 605~nm (red)
for the larger particles. In absence of a salt concentration gradient,
both populations of particles were advected by the flow and remained confined
in the same regions of the channel where they were initially
injected (Fig.\,\ref{fig:size}b). Upon imposition of a salt contrast
($c_{\scriptscriptstyle L}=0.1\,$mM, $c_{\scriptscriptstyle H}=10\,$mM), the larger (red) particles
were strongly focused at the center of the channel where they formed two intense peaks. Conversely,
the smaller (yellow-green) particles did not form any accumulation peak and only a small fraction of them
drifted toward the center.
Furthermore, the two colloidal bands made of larger particles, expanded
along the transverse direction
towards the higher salt concentration (outer) regions of the channel due to diffusiophoresis~\cite{Abecassis2008d},
with two additional focusing peaks forming at these locations.
On the other hand, the colloidal bands made of smaller particles did not drift
towards the outer regions because of their smaller
diffusiophoresis coefficient.  As a result, diffusiophoresis and diffusioosmosis
could be effectively exploited for the microfluidic separation and sorting of the two populations of particles according to their size.

\subsection{Detection of liposome zeta potential and membrane composition in double-junction devices}

The range of applications of the double-junction device can be expanded further
by leveraging the dependence of the diffusiophoresis coefficient on zeta
potential, which is a key property of colloidal system.
For instance, synthetic nanoparticles are widely adopted as drug-delivery
systems and their zeta potential must be carefully tuned to control
the way the drug-loaded nanoparticles target, interact and adsorb onto cell
membranes~\cite{honary2013effect1,honary2013effect2}.
Furthermore, natural nanoparticles
that are present in body fluids, such as extracellular vesicles,
have a great potential as
biomarkers~\cite{lane2018extracellular,thompson2016extracellular,nawaz2014emerging,szabo2017extracellular},
and the characterization of their zeta potential, which depends on their
membrane composition, is paramount in understanding their biological origin and
functions.
In these experiments, we used nano-sized unilamellar liposomes, which are often used as drug
carriers~\cite{sercombe2015advances,guimaraes2021design}
and cell membrane models~\cite{el2008liposomes}.
Their surface charge and, thus zeta potential, can be easily
tuned by adjusting the lipid membrane composition, therefore these
nanoparticles are suitable for investigating the effect
of zeta potential on the focusing phenomenon in the double-junction device.

In the first set of experiments, we fabricated negatively
charged liposomes by adding 10 $\%$ mol fraction of the anionic phospholipid
1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS)
to the neutral DPPC phospholipid ($\textit{d}$ = 166 $\pm$
4 nm, $\zeta$ $\approx$ -57 mV, polydispersity index $\approx$ 0.1). The phophoserine
headgroup (PS) was specifically chosen as its presence in the outer leaflet of the membranes
of biological particles can be associated with pathological and physiological processes,
such as in tumor-derived exosomes ~\cite{maia2018exosome} and during cell apoptosis~\cite{fadeel2009ins}.
The vesicles were dispersed in a low salt concentration ($c_{\scriptscriptstyle L}$ = 0.01 mM)
LiCl solution buffered with HEPES salt and EDTA chelating agent (pH = 8.15).
The aqueous stream of charged liposomes was pumped in
the outer channels of the upstream junction, whereas the same
low salt concentration solution without liposomes was injected in the
inner channel of the device. Finally, a high salt concentration ($c_{\scriptscriptstyle H}$ = 6.65 mM) LiCl solution, also buffered
with HEPES salt and EDTA, was pumped instead in the outer channels of the downstream junction.
The fluorescence intensity profiles along the transverse direction are showed in Fig.~\,\ref{fig:liposomes}a.
It can be observed that charged liposomes display a similar behavior to the one observed for
polystyrene nanoparticles.
Upon imposition of a salt gradient (red curves), peaks of accumulated liposomes formed
and converged to the center of the device ($|x|/w_m\le0.2$) and away from the colloidal bulk streams ($|x|/w_m>0.2$).
Conversely, when the salt concentration was the same throughout the
device (blue curves), liposome peaks did no form  and no particles migrated toward the inner region of the channel.
\begin{figure}[tb!]
\begin{center}
\includegraphics[width=\columnwidth]{Fig6.pdf}
\end{center}
\caption{(a) Normalized fluorescent intensity profiles along the transverse direction $x$ and at varying
distances $z$ from the downstream junction
without (blue curves) and with (red curves) a salinity gradient.
(d) experimental focusing parameter against zeta potential for DOPC
(blue) and DPPC (red) based liposomes with varying anionic DOPS concentrations
(navy box = 1 PS, orange = 2 PS, purple = 10 PS .(e) experimental focusing
parameter against the DOPS anionic lipid content. Fabricated liposomes had an average size of $\textit{d}$ = 166 $\pm$ 4 nm (SE).
\label{fig:liposomes}} \end{figure}
Note that for liposomes, a higher salt contrast
($c_{\scriptscriptstyle H}/c_{\scriptscriptstyle L} = 333$) was adopted  in comparison to the one applied in the experiments with
carboxylated polystyrene nanoparticles ($c_{\scriptscriptstyle H}/c_{\scriptscriptstyle L} = 100$).
Indeed, in agreement with previous studies~\cite{shin2019osmotic,rasmussen2020size},
the migration speed of liposomes under salt gradients is typically smaller that the one of polystyrene
nanoparticles with comparable zeta potential, therefore higher salt contrasts are
required. This is likely due to the soft and water-permeable nature of the liposomes that may
trigger additional migration mechanisms, such as osmophoresis~\cite{anderson1986transport},
or affect the diffusiophoresis response through membrane permeability~\cite{anderson1983movement,yeh2018diffusiophoresis},
membrane viscosity and vesicle shape deformations.
To confirm that the imposed salt contrast did not affect the liposome stability and size in our experiments,
a liposome solution in low salt concentration ($c_{\scriptscriptstyle L}$) buffer was analyzed
via dynamic light scattering before and after
dilution in high salt concentration ($c_{\scriptscriptstyle H}$) buffer, resulting in no detectable changes in the particle size distribution.
Interestingly, the inset in Fig.\,\ref{fig:liposomes}a shows that when using zwitterionic DPPC liposomes ($\zeta=+10\,$mV) instead of
negatively charged DPPC-DOPS liposomes, no focusing effect is observed under a salinity
gradient. This observation is consistent with our physical interpretation of the particle
focusing phenomenon. Indeed, DPPC liposomes in the buffer solution carry a very weak positive charge and,
therefore, do not migrate by diffusiophoresis towards the top and bottom non-zero charged walls of the channel.
In absence of a particle accumulation nearby the walls, the diffusioosmosis flows
at the walls do not affect the colloid distribution in the device and no particles are
directed toward the center of the channel ($|x|/w_m\le 0.2$).
Remarkably, this finding could be exploited for the microfluidic separation of negatively charged liposomes
from uncharged or positively charged ones

In another set of experiments, we investigated the effect of the lipid
composition of the liposome membrane on  particle focusing.  Specifically, we
adjusted the zeta potential of the liposomes by varying the amount of charged
lipid content in the membrane composition, and we controlled the
viscosity/fluidity of the membrane by using lipid mixtures with a fluid/gel
phase transition temperature either above or below the room temperature. Since
altering the zeta potential of the liposomes affect significantly their
diffusiophoresis mobility, it should be possible to correlate the charged lipid
content with the intensity of the focusing effect in the device. On the other
hand, it is known that the diffusiophoresis speed depends also on the Newtonian
and Maxwell stress balance at the particle
surface~\cite{yang2018diffusiophoresis}, which in turn depends on
the viscosity of the membrane. However, to date the role of membrane
viscosity on the diffusiophoresis of lipid vesicles or living cells has yet to be explored.
To carry out this analysis, we considered six
different liposome populations at 1,2 and 10$\%$ DOPS (charged lipid) mole fraction added to
zwitterionic lipids, either 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)
for a disordered fluid phase membrane or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)
for an ordered gel phase membrane.
Three independent samples were produced for each liposome population, and for each sample both
the zeta potential and the corresponding focusing parameter were determined. All liposome populations had
similar size ($\textit{d}$ = 166 $\pm$ 4 nm) and polydispersity index.
Fig.\,\ref{fig:liposomes}b and Fig.\,\ref{fig:liposomes}c show how the focusing parameter $I$ is positively correlated with
the particle zeta potential and the DOPS (charged lipid) mole fraction. Remarkably, for a given DOPS concentration,  there is no
statistically significant difference between the focusing parameters observed for DOPC-DOPS fluid-like membrane vesicles (blue bars/symbols)
and for DPPC-DOPS gel-like membrane vesicles (red bars/symbols), thereby showing the irrelevance of the liposome membrane viscosity
for the diffusiophoresis transport under the examined conditions.
The linear regression (dashed line) between liposome zeta potential and focusing parameter is given by
\begin{equation}
\bar{I}=-0.0116\,\zeta
\label{eq:I_zeta}
\end{equation}
with $\zeta$ expressed in millivolt.
Eq.\eqref{eq:I_zeta} can be used as a calibration curve for the microfluidic detection of the zeta potential of similarly-sized
particles, whereby the focusing parameter $\bar{I}$ is measured experimentally to quantify the zeta potential according to the following relation
\begin{equation}
\zeta=-86.2\,\bar{I}
\label{eq:zeta_I}
\end{equation}
Furthermore, we conducted an electrophoretic light scattering analysis to correlate
the zeta potential of DOPC-DOPS vesicles with the DOPS (anionic lipid) content in the membrane (Fig.\,\ref{fig:liposomes}d).
As the DOPS mole fraction increases, the magnitude of the zeta potential of liposomes increases, and
eventually it plateaus at ca. 8-10$\%$ DOPS content. Beyond this point, adding more DOPS
to the membrane does not affect the zeta potential, due to the formation of a charged condensed layer of Na$^+$
counterions around the outer leaflet of the liposomes~\cite{lutgebaucks2017characterization}.
On the other hand, the zeta potential is highly sensitive to the DOPS content
at low anionic lipid concentrations ($\le\%3$). This suggests a strategy for the application of the double-junction device
for the quantification of small amounts of DOPS lipids in the outer leaflet membranes of liposomes.
Indeed, for low anionic lipid concentrations ($\le\%3$), the relation between zeta potential $\zeta$ (expressed in millivolt)
and the DOPS mole fraction $\left[\textrm{DOPS}\right]$ (expressed in percentage values)
can be well approximated by the following linear relationship,
plotted as a dashed line in Fig.\,\ref{fig:liposomes}d,
\begin{equation}
\zeta=-10.9 \, \left[\textrm{DOPS}\right]-19.0
\label{eq:zeta_DOPS}
\end{equation}
By combining Eq.~\eqref{eq:zeta_DOPS} and Eq.~\eqref{eq:zeta_I}, it follows
\begin{equation}
\left[\textrm{DOPS}\right] = 7.91\, \bar{I} - 1.74
\label{eq:DOPS_I}
\end{equation}
which allows one to estimate the DOPS lipid mole fraction from the experimental measurements of the focusing parameter $\bar{I}$.
To conclude,  Eq.~\eqref{eq:zeta_I} and Eq.~\eqref{eq:DOPS_I} show how
the double-junction device can be used effectively for the quantitative estimate of both the zeta
potential and the DOPS lipid content of the outer leaflet of liposome membranes.

\section{CONCLUSIONS}

We described an unreported mechanism where diffusiophoresis and diffusioosmosis
are closely intertwined, leading to a strong transverse focusing of nanoparticles
in a single $\Psi$-junction microchannel under continuous and steady axial flow conditions.
Parallel electrolyte streams are merged at the junction of the device to generate a chemical gradient in both the transverse and
vertical directions. As a result, the particles first migrate vertically by diffusiophoresis from the bulk towards the top and bottom walls,
and subsequently undergo a transverse horizontal migration along these walls
driven by diffusioosmosis.
The remarkable coupling of diffusiophoresis and diffusioosmosis along two perpendicular directions
allows us to take advantage of the relatively weak diffusioosmotic slip velocities
in a pressure-driven microfluidic flow without resorting to dead-end or nano-sized channels.
Indeed, here it is the vertical diffusiophoretic migration that confines the particles nearby the
charged walls where the effects of diffusioosmotic flows are the most intense.
Consequently, one can avoid the most common drawbacks associated with dead-end pores or nano-confined channels,
such a risk of device obstruction and clogging, costly device fabrication procedures and difficult recovery of the
colloidal sample.
By means of epi-fluorescence microscopy, two accumulation peaks are formed and their separation distance
decreases with the distance from the channel inlet, eventually reaching a
plateau value that depends on the size and $\zeta$-potential of the colloids.
Those peaks are of an intrinsically different nature of those
observed in previous works~\cite{Abecassis2008d}, the dynamics of which was
exclusively driven by diffusiophoresis.

We also showcased the exploitation of this novel mechanism
for the continuous separation and characterization of colloidal particles.
A proof-of-concept double-junction device was developed and used for the accurate measurements of
the diameter of colloidal beads with same $\zeta$-potential, based on the measurement of an ad-hoc,
purposely defined, focusing parameter $\bar{I}$. We also demonstrated how the
dependence of the transverse drift dynamics of the accumulation peaks on the colloid size
can be further leveraged to separate large particles ($1.098\,\mu$m) from
smaller ones ($36\,$nm) in a bi-modal mixture. Moreover, the setup is proven
to allow for a reasonable assessment of the $\zeta$-potential of same size
particles through the measurement of the focusing parameter $\bar{I}$. Based
on this latter principle, we eventually showed how, in the case of liposomes, the
measurement of the $\zeta$-potential can be used to assess the
chemical composition of the membrane (here the percentage of charged DOPS lipid
content), at least in the low concentration limit.
Note that, whilst previous studies allowed only for batch measurements of particles located in dead-end pores or open nanochannels,
our double-junction device enables the online, continuous and high-throughput characterization
of particles directly within the colloid stream. This also facilitates the recollection
of the analyzed sample for further off-chip downstream analysis.
Finally, we showed how, under the examined
experimental conditions, the fluid-like or gel-like states of the membrane, and thus the membrane viscosity,
does not affect the diffusiophoretic response of the liposomes.

We envisage that this study will open up new exciting ruotes for the use of diffusiophoresis
and diffusioosmosis for the microfluidic manipulation and characaterization of both synthetic and natural particles.
Our microfluidic devices can unlock a wide scope of possibilities related to bio-oriented applications,
such as the pre-concentration, sorting, sensing and analysis of biological entities, including
liposomes, extracellular vesicles and bacteriae. By relying on the chemical energies of the electrolyte
solutions rather than on external energy sources
and by adopting cheap and easy-to-fabricate microfluidic chips, the proposed particle manipulation and characterization
strategies naturally lend themselves to the development of portable, cost-effective, point-of-need microdevices
for chemical and biochemical analysis, diagnostics, drug screening and drug delivery applications.

\section{METHODS}
\subsection{Materials}

Invitrogen\texttrademark~ FluoSpheres\texttrademark~ , carboxylate-modified nanoparticles, red fluorescent (580/605), 2 $\%$ solids, were purchased from ThermoFisher scientific at various sizes (20,100,200,500,1000 nm). In additon, Invitrogen\texttrademark~ FluoSpheres\texttrademark~ , yellow-green fluorescent (505/515), 2$\%$ solid, 20 nm carboxylate-modified nanoparticles was also purchased for separation experiments from the same supplier. Lithium chloride salt (LiCl, 99\%) used for diffusiophoresis experiments was purchased
from Acros Organics. Aqueous liposome solutions prepared with buffer salt,
HEPES and chelating agent EDTA were purchased from Sigma Aldrich. Both
lipophilic dye, 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO$_{c_{18}}$), used
for staining liposomes and chloroform (99\%) used for preparing lipid films
were purchased from Sigma Aldrich. RTV 615 polydimethyl siloxane used for the
fabrication of microfluidic devices was purchased from Techsil, UK. Stand-alone
liposomes were made using 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or
1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and charged liposomes were
prepared with the addition of 1,2-dioleoyl-sn-glycero-3-phospho-L-serine
(DOPS)anionic phospholipid, all purchased from Avanti Polar Lipids.

\subsection{Fabrication and operation of the microfluidic devices \label{seubsec:mufluidic_device}}

Standard photo and soft lithography techniques were employed in manufacturing
the microfluidic devices. Briefly, the drawings of both one and two-junction
devices were printed on a photomask film (Micro Lithography Services, UK)
and subsequently used to produce an SU-8 master mould
of ca. 50 $\upmu$m thickness on a silicon wafer (Inseto, UK). Imprinted
polydimethylsiloxane (PDMS) channels are then made via replica molding by
heating a PDMS:curing agent (9:1) mixture on top of the SU-8 master could. The
channels are then irreversibly bonded to a microscope slide by using a plasma
cleaner (Harrick Plasma, UK) at 18W power for 1 minute. All devices
have a nominal depth of 50 $\upmu$m and a total channel width of \textit{w} =
400$\,\upmu$m.
For the single junction chip,
the width of the main channel and the inner inlet channel are $w=400\,\upmu$m and $w_{i}=200\,\upmu$m, respectively, whereas the
width of the outer inlet channels are $(w-w_i)/2=100\,\upmu$m.
For the two-junction device, the width of the main channel is $w=400\,\upmu$m.
For the downstream junction, the width of the inner channel and
outer inlet channels are $w_{m} = 250\,\upmu$m and $(w-w_m)/2=75\,\upmu$m, respectively.
For the upstream junction, the width of the inner and outer inlet channels
are $w_{i} = 100\,\upmu$m and $(w_m-w_i)/2=75\,\upmu$m, respectively.
Aqueous solutions are injected into the device inlets at a constant flow rate
of 3.65 $\upmu$l/min by means of syringe pumps (Harvard, USA).
To generate a steady state salt gradient, a flow switch valve
is used to swap the inner stream from a low ($c_{\scriptscriptstyle L}$) to high ($c_{\scriptscriptstyle H}$) salt
concentration solution.

\subsection{Nanoparticle sample preparation~~\label{subsec:sample prep}}

Deionised water (18.2 M$\Omega$\,cm) produced from an ultrapure milli-Q grade
purification system (Millipore, USA)  was used to prepare all aqueous
solutions. Carboxylated polystyrene particles (Invitrogen\texttrademark~
FluoSpheres\texttrademark~, red fluorescent (580/605) or green fluorescent
(505/515), 2 $\%$ solids) were diluted in a 0.1 mM LiCl solution at a particle
concentration of 0.002\% v/v for the $1\,\upmu$m particles and $0.02\%$ v/v for
particles of other diameters.  Liposomes were prepared using standard thin film
hydration ~\cite{bangham1967} and subsequent extrusion techniques
\cite{hope1985ex} . In short, lipids and lipophlic dye (DiO$_{c_{18}}$) are
dissolved in chloroform and mixed at appropriate ratios. The chloroform is
evaporated using a constant flow of N$_{2}$. The dried lipid film is desiccated
for a minimum of 3 hours before hydration and dilution using a 0.01 mM LiCl +
5$\upmu$M EDTA + 5$\upmu$M HEPES solution, pH = 8.15. The liposome suspension
is then vortexed at 1200 rpm for 60s and extruded 21 times through a 200 nm
polycarbonate membrane filter (Avanti Polar Lipids, US) to maintain an average
polydispersity index (PDI) of 0.1.

\subsection{Image acquisition and processing~~\label{subsec:processing}}

An inverted optical microscope (TE300, Nikon) equipped with a x10 objective
lens (0.25 NA) is used to image particle dynamics at different distances from the
junction.  A fluorescent lamp (CoolLED pE300) is used to excite the sample
which allows the collection of fluorescent intensity data via a CCD camera
(Ximea MQ013MG-ON). Collected data is in the form of 1264 x 1016 px, 16 bit
TIFF images. The depth of field  of the microscope -- i.e. the thickness of the slice region that is in acceptably
sharp focus in the micrographs -- can be calculated as~\cite{inoue1995microscopes} $n_{ind}
\, \lambda_{em} / NA^2 + n_{ind}\,e/(M\cdot NA)\simeq 10~\upmu$m, where $n_{ind}=1$ is the
refractive index of the objective immersion medium (air), $\lambda_{em}=510$~nm
is the nanoparticle emission wavelength, $e=4.8\,\upmu$m is the pixel pitch of
the CMOS camera, $NA=0.25$ and $M=10$ are the objective numerical aperture and
magnification, respectively.

A PicoQuant MicroTime 200 time-resolved confocal microscopy platform,
built around an Olympus IX 73 microscope, was used to acquire confocal images in
the x-y plane, as shown in~\figurename~\ref{fig:Fig1}. A plan N 40x water immersion
objective lens (0.65 NA) was used to take 1024 x 1024 px,
32 bit TIFF images. A monodirectional scanning pattern was used with a learning time of 5 seconds and a dwell time of 2 seconds.
Fluorescent intensity profiles were normalized by first subtracting the
background noise and then dividing by the average intensity of the
bulk obtained from a no salinity gradient configuration. All fluorescent image shown in figures were processed using ImageJ (contrast enhancement, LUT colour change).

\subsection{Particle characterisation~~\label{subsec:characterisation}}

All size and zeta potential measurements were performed using a ZetaSizer nano
ZS (Malvern Panalytical) at 25\textdegree C. All samples were analyzed a
minimum of 3 times using the monodomal measurement mode for a monodisperse
single population of particles.
The instrument provided the zeta potential values calculated according to the Smoluchowski's theory for which
the Debye length is much smaller than the particle size. The zeta potential
values were corrected to account for the finite size of the Debye length
according to Henry's model\cite{hunter2001foundations} .

\subsection{Numerical methods}
Numerical simulations were performed in Comsol Multiphysics according to the
procedures detailed in our previous work~\cite{singh2020reversible} .  Briefly,
the 3D computational domain consisted in a rectangular channel of width
$2w_i=400\:\upmu$m, depth $h=52\:\upmu$m and length $25 w_i + 5h$. The
hydrodynamic velocity, $\mbox{$\bm u$}$, pressure $p$, salt concentration $c$ and
particle concentration $n$ were calculated by solving the steady-state
Navier-Stokes equation and the advection-diffusion equations for $c$ and $n$.
At the channel inlet, the boundary condition for the velocity field was
$\mbox{$\bm u$}=\mbox{\boldmath$u$}_{\mbox{\tiny{inlet}}}$, with $\mbox{\boldmath$u$}_{\mbox{\tiny{inlet}}}$ the fully developed velocity field at a cross
section of the rectangular channel perpendicular to the flow direction and with
average velocity $U_0$.  The boundary conditions at the channel inlet for the
salt and particle concentration fields are $c=c_{\scriptscriptstyle H}$ and $n=0$ for the outer flow
region (i.e., $|x|>w_i/2$) and $c=c_{\scriptscriptstyle L}$ and $n=n_0$ for the inner flow region (i.e., $|x|\le w_i/2$). At the channel outlet,
the zero normal gradient boundary condition for the pressure, salt and particle
concentrations were imposed. At the remaining walls, the slip boundary
condition $\mbox{$\bm u$}=-\Gamma_{\mbox{\tiny DO}} \mbox{$\bm \nabla$} (\ln c) $ was applied together with the zero
flux condition for the salt and particle concentration fields.  The channel
outlet was located at 5 times the channel depth $h$ from the cross section
$z/w_i=25$ to ensure that the boundary conditions at the channel outlet do not
affect the fields near that section.
The particle diffusiophoresis coefficient $\Gamma_{\mbox{\tiny DP}}=291\,\upmu$m$^2$/s was calculated according
to the procedure detailed in our previous work~\cite{singh2020reversible} ,
 where the formula provided by Prieve and co-workers\cite{prieve1984motion} was used to
account for the particle size effect on $\Gamma_{\mbox{\tiny DP}}$.
A diffusioosmosis coefficient of $\Gamma_{\mbox{\tiny DO}}=1165\,\upmu$m$^2$/s was chosen for the channel walls to
obtain a good quantitative match between experimental results and numerical predictions.

\begin{acknowledgement}
This research was supported by the EPSRC (EP/S013865/1)

\cite{Note-1}

\end{acknowledgement}

\begin{suppinfo}

The supplemental file details the results of (i) the control experiments in a single
$\Psi$-junction device without salt concentration gradient, (ii) the experimental test
in a single $\Psi$-junction device with colloidal particles dispersed in the
higher salt concentration stream.

\end{suppinfo}

\section{Supplementary Information}

\subsection{Control experiment in a single $\Psi$-junction chip}

\begin{figure}[b!]
\begin{center}
\resizebox{6.5in}{!}{\input{Fig.s1.pdf_tex}}
\end{center}
\caption{Particle dynamics under no salinity gradient conditions $\nabla$c =
0. (a) schematic diagram of a single $\Psi$-junction microchip, where low salt
concentration is injected in all channels with carboxylate polystyrene nanoparticles (NPs) present in the
centeral channel only.
(b) Top view epi-fluorescence images taken at different
distances downstream the junction for the flow configuration shown in (a), scale bar =
75 $\mu$m. (c) Confocal image taken at $z/w_{i}$ = 25 for the flow configuration shown
in (a), scale bar = 10 $\mu$m.
\label{fig:FigS1}
} \end{figure}

A control experiment with no salt concentration gradient
was conducted by using the same $\Psi$-junction microchip in the main text.
A colloidal suspension at low salt concentration ($c_{\sst L}$) was injected in the inner channel, whereas
an aqueous solution with identical level of salinity ($c_{\sst L}$) was pumped
in the outer channels (Fig.\,\ref{fig:FigS1}a).
In the absence of a chemical gradient, the colloids remained homogeneously distributed
within the inner region of the channel and the colloidal band maintained a constant width downstream
the junction (Fig.\,\ref{fig:FigS1}b).
No peak formation and subsequent convergence were
visible and the particle distribution profile along the channel depth
remained uniform (Fig.\,\ref{fig:FigS1}c).
This is because no salinity gradient exists in
any direction. Consequently,  electrokinetic phenomena such as
diffusiophoresis and diffusiosmosis do not occur in the system.
Furthermore, the flow is characterized by
a high Peclet number, $Pe=U_0\,w /D_c\simeq10^6$, where $D_c$ is the particle diffusivity given by
$D_c = k_b T / 6\pi\mu a=2.4\times10^{-12}\,$m$^2$/s with $\mu=0.9\times10^{-3}\,$Pa~s the solution viscosity
and $a$nm the particle radius. Therefore
particle diffusion is negligible compared to convective transport,
and since both inertia and gravity effects are also negligible, the colloids behave as passive tracers.

\subsection{Salinity conditions of NP solution for peak formation}
\begin{figure}[b!]
\begin{center}
\resizebox{6.5in}{!}{\input{Fig.s2.pdf_tex}}
\end{center}
\caption{disappearance of focusing mechanism when colloids are in high
salinity. (a) schematic diagram of a single $\Psi$-junction microchip, where
low salt is injected in the inner channel and high salt with colloids being
injected in the outer channels. (b) epi-fluorescence images taken at different
distances downstream the junction  for the flow configuration in (a), scale bar
= 75 $\mu$m. (c) the dynamics of previously reported particle migration against
the square root of the longitudinal distance downstream the junction.
\label{fig:FigS2}} \end{figure}

We find that peak formation due to our reported focusing effect does not occur
when PS-COOH nanoparticles are dispersed in high salt ($c_{\sst H}=10~$mM)
solution in the outer channels, but rather in low salt ($c_{\sst L}=0.1~$mM) in
the inner channels (figure S2a). Consequently,
this led to the development of the two $\Psi$-junction microchip for
nanoparticle fractioning to target advanced applications. Moreover, we observe
a previously reported particle accumulation effect that has been outlined in
the main text. Figure S2c substantiates this, as accumulated particles diverge
towards higher salinity regions at a $\sqrt{z}$ trend downstream the junction.

\clearpage
\newpage

\end{document}

redpajama_set_name: RedPajamaArXiv


Libraries lead to strong communities. During National Library Week, Fruitport District Library will be collecting non-perishable items for the Food Pantry at Fruitport Christian Reformed Church. Please drop off donations during the library's open hours. Thank you.


IT'S NATIONAL STRAWBERRY SUNDAE DAY and I did pour it into a martini glass!
And because you can garnish it with a cheesecake filled strawberry!
I'm found of Apple Cocktails. I'm fond of apples. I'm not fond of applesauce. In fact, I kind of hate applesauce, but a friend gave me some of her homemade applesauce (more like a quart) and I had to find a way to use it and not hurt her feelings. So I came up with this recipe for an Apple Cobbler Martini. It uses a quarter of a cup of applesauce for each cocktail so I managed to use up that applesauce gift pretty fast. Now I'm hoping I get the applesauce as a gift again, lol.
Inspired by my Baked Apple Tarragon Chicken Breast recipe this cocktail recipe includes apple vodka, lemon, some spices, sugar, some sautéd apples and, of course, applesauce.
Peel and slice the apples. Melt the butter in a saute pan, add the apples and saute for 5 - 8 minutes or until almost cooked through. Add the sugar, half the spices and reduce until the sugar gets well caramelized. Set aside to cool while you prepare your cocktail.
Blend all but 3 or 4 of the caramelized apples into the applesauce and add 1/4 cup to each cocktail you're making. Save the unblended ones for the garnish.
Fill a cocktail shaker with ice then add the applesauce, apple vodka, orange juice, lemon juice, the rest of the spices and shake until smooth.
Pour into your chilled glass (do not strain, it's futile), garnish with a couple of the caramelized apples and serve.
and the best place for those is on the rim of a martini!
was inspired by how I used to eat Oreos.


The Queen's Gurkha Engineers (QGE) said farewell to its outgoing Commandant, Lieutenant Colonel JW Hawkins RE and Gurkha Major Major Buddhi Bahadur Bhandari MVO and their families.
On the 1st June 2018 a tow out of barracks by members of the Regiment took place for the Gurkha Major before his inspirational speech to the Regiment.
We wish both Lieutenant Colonel JW Hawkins RE and Gurkha Major Major Buddhi Bahadur Bhandari MVO the very best for the future.


Preheat oven to 350�F (Use a slightly cooler oven for coated or dark pans).
Using an electric mixer, beat the eggs until thickened and light colored.
Gradually bean in the sugar, then the rest of the liquids.
Beat in flour and then baking powder.
Pour the batten into the pan and bake for approximately 45 minutes, or until a toothpick comes out clean.
Cool slightly and then turn upside down to remove from pan.


↑ "The World Factbook". Central Intelligence Agency. 1 February 2014. https://www.cia.gov/library/publications/the-world-factbook/geos/uk.html. Retrieved on 23 February 2014.
↑ "Countries within a country". Prime Minister's Office. 10 January 2003. http://webarchive.nationalarchives.gov.uk/+/http://www.number10.gov.uk/Page823.
↑ "Working with Overseas Territories". Foreign and Commonwealth Office. http://www.fco.gov.uk/en/about-us/what-we-do/overseas-territories. Retrieved on 3 May 2011.


Which one's right? Well, both. That's why it's important to know the facts before taking a hard stance.
There are whole soy foods and processed soy foods. Processed food in general is something we should all strive to stay away from. Especially with a recent study showing 'ultra-processed' food could increase your risk for cancer. But unlike the standard processed foods, (cereal, sodas, chips, etc.) processed soy can be hard to detect. Doctor Oz puts in plainly by saying, if you see "soy protein" on the nutritional label – it's processed.
That includes your soy protein powders and bars.
Your whole soy food, however, can be great for you. Local nutrition coach, Brenda Fikry, says to aim for soy products that are close to their natural state.
Knowing what to eat and how much to eat should go hand-in-hand. Too much of anything – even water – can be bad for you. Soy is no different.
1 to 2 servings of soy is Fikry's recommendation. Eating over 4 or 5 servings of soy a day could put you in a danger zone.
This includes our lattes and iced drinks we get at coffee shops. Generally, if you get anything over a 16 oz (2 cups) in soy milk, you've exceeded your daily recommendation.
And unlike chicken, beef and pork, soy is low in saturated fats. It also has no cholesterol and is a heart healthy food. For some, it can also lower blood pressure.
"The variety is the key to getting different vitamins and minerals rather than getting the same ones over and over," says Fikry.
First off, labels with the word "natural" are probably not what you think.
According to USDA standards, a food that's labeled "natural" cannot contain preservatives, artificial ingredients and it has to be minimally processed.
However, that product can still have growth hormones, chemicals and antibiotics in it.
And "all natural" literally means nothing. The USDA hasn't defined it so it's probably no different than a product marked "natural". However, there is no guarantee it goes through the same regulations as "natural" products do.
With that said, be a critic. Take that extra 30 seconds and scan the ingredient label.
If your food says "all natural" and has things like sucralose, saccharin, aspartame, acesulfame, sodium nitrite, sodium nitrate…. come on now.
Brenda lives in Tampa with her husband Mohamed and dog Mylah. She prefers being called a nutrition "coach" because she loves empowering, motivating and walking alongside her clients as they reach their goals.


Xbox 360 3 red blinking lights Four. Cast your eye also on the power supply. When you start the console the light power supply should turn green even if the 3 red flashing led on the console. Today about an hour ago i suffered what many gamers across the world have suffered i got three lights flashing red on my xbox 360. If i was your typical gamer the customer service rep told me Microsoft has finally responded to xbox 360 hardware problems by extending the worldwide warranty to three years for systems with quota general hardware failure indicated by three flashing red lightsquot..
Xbox 360 3 red blinking lights Lo and behold microsoft corp. Answered back by expanding the global xbox 360 warranty coverage to 3 years from date of purchase for a general hardware failure. This is apparently indicated by three Reader matthew just found out about this the hard way i bought my xbox 360 pro at xbox itself and see flashing red coming from it. Now at this point im thinking my time has come for the red After all the playstation 3 and xbox 360 did have some missteps along the way. Here in no particular order are console troubles that we may never forget. The last thing you want to see when you.
Xbox 360 3 red blinking lights Los angeles reuters microsoft corp. Msft.o said on thursday said it would take a more than 1 billion charge to fix an unacceptable number of repairs to its xbox 360 video game indicated How to tell which xbox 360 error code is being displayed step 1 note the colors inside of the light ring on the consoles face. Xbox 360 error codes flashing at the same time indicates the In response to all the recent buzz about the high failure rate of their xbox 360 console microsoft today announced if your console suffers from three flashing red lights on the ring of light.
She buys it. As you.
It's possible to get or download caterpillar-wiring diagram from several websites. If you take a close look at the diagram you will observe the circuit includes the battery, relay, temperature sensor, wire, and a control, normally the engine control module. With an extensive collection of electronic symbols and components, it's been used among the most completed, easy and useful wiring diagram drawing program. Xbox 360 3 Red Blinking Lights. The wiring diagram on the opposite hand is particularly beneficial to an outside electrician. Sometimes wiring diagram may also refer to the architectural wiring program. The simplest approach to read a home wiring diagram is to begin at the source, or the major power supply. Basically, the home wiring diagram is simply utilized to reveal the DIYer where the wires are.
In a parallel circuit, each unit is directly linked to the power supply, so each system gets the exact voltage. There are 3 basic sorts of standard light switches. The circuit needs to be checked with a volt tester whatsoever points. Xbox 360 3 Red Blinking Lights. Each circuit displays a distinctive voltage condition. You are able to easily step up the voltage to the necessary level utilizing an inexpensive buck-boost transformer and steer clear of such issues. The voltage is the sum of electrical power produced by the battery. Be sure that the new fuse isn't blown, and carries the very same amperage.
The control box may have over three terminals. After you have the correct size box and have fed the cable to it, you're almost prepared to permit the wiring begin. Then there's also a fuse box that's for the body controls that is situated under the dash. Xbox 360 3 Red Blinking Lights. You will find that every circuit has to have a load and every load has to have a power side and a ground side. Make certain that the transformer nameplate power is enough to supply the load that you're connecting.
Lights on xbox 3 xbox 360 4 red lights xbox power supply red-light xbox 360 one red-light power reset xbox 360 3 red lights xbox 360 red ring codes jtag xbox 360 red-light white xbox 360 console.


Former India captain Bishen Singh Bedi has appealed to the Board of Control for Cricket in India (BCCI) to take blind cricket under its fold. The Cricket Association for Blind in India (CABI) is yet to be recognized by the Indian government.
The conclave was to celebrate and honor the Blind Indian cricket team, who are champions of the 5th ODI World Cup. Over 80 cricketers from across India were present.
Bedi gave the example of former India captain Tiger Pataudi, who played international cricket after losing an eye in a car accident.
Chetan Chauhan, Minister of Sports and Skill Development in Uttar Pradesh, offered full support to the Indian blind team in providing them jobs.
Former middle-order batsman Ajay Jadeja said that information about blind cricket should reach every section of the society, including schoolgoing children and everyone should experience playing this game.


Executives of the Pan Am Corporation met with the chairman of Trans World Airlines, Carl C. Icahn, soon after getting his latest buyout offer, a Pan Am spokesman said. The spokesman, Jeff Kriendler, declined to provide any details about the meeting.
Over the weekend, Mr. Icahn announced plans to sell all of T.W.A.'s London routes and other assets to American Airlines in a package worth $625 million. At the same time, Mr. Icahn said he had written Pan Am's chairman, Thomas G. Plaskett, with an offer to buy Pan Am's 150 million outstanding shares for $1.50 a share in cash and $1 a share in preferred stock or notes.


text:
Yuki Yuna is a Hero Season 2 Episode 7
Yuna Yuki and the others at the Sanshu Middle School Hero Club work hard at their club activities, and spend their everyday life as usual.
Episode Title: Spectacular Days
Several hundred years ago, humans were nearly exterminated by Titans. Titans are typically several stories tall, seem to have no intelligence, devour human beings and, worst of all, seem to…
Genre: Action & Adventure, Animation, Drama, Mystery, Sci-Fi & Fantasy, War & Politics
Erika Shinohara has taken to lying about her romantic exploits to earn the respect of her new friends. So when they ask for a picture of her "boyfriend," she hastily…
Psychic Detective Yakumo is a novel by Manabu Kaminaga published in Nihon Bungeisha with illustrations by Katoh Akatsuki and later in Kadokawa Bunko with cover illustrations by Yasushi Suzuki. The…
Genre: Action & Adventure, Animation, Drama, Mystery
In the town of Lindworm where monsters and humans coexist, Dr. Glenn runs an exemplary medical clinic for monster girls with his lamia assistant, Sapphee. Whether receiving a marriage proposal…
Magic Kaito: Kid the Phantom Thief
KissAnime Review: My favorite anime from year 2010. Magic Kaito: Kid the Phantom Thief is by far the best online anime production I've ever seen. There is anime in my…
Genre: Animation, Crime, Mystery
Tsukasa, a college student, is rescued from an attack by a devil, one of many vampires that can blend in among the human population. Anzai, her savior, is a half-devil…
Barbie: Life in the Dreamhouse
The series is set as a reality TV-esque show following Barbie, her sisters and her friends in the day-to-day activities that take place in the Dreamhouse and surrounding areas. Much…
Dai Shogun – Great Revolution
In the late Edo period, Japan had experienced an unprecedented crisis by Kurofune (Black Ships), the ships from foreign countries. But a giant robot called Onigami, which has existed since…
The "Seven Deadly Sins"—a group of evil knights who conspired to overthrow the kingdom of Britannia—were said to have been eradicated by the Holy Knights, although some claim that they…
When Tony Stark branches his company into Japan, he is opposed by the nefarious Zodiac organization. It's up to Stark's Iron Man to defeat the Zodiac, and defend Japan. KissAnime…
Twenty years ago, Shokichi Komachi was part of the Bugs 2 mission to Mars that discovered Terra Formars, human-cockroach hybrids that resulted from a terraforming accident. Shokichi was one of…

redpajama_set_name: RedPajamaCommonCrawl


text:
Giroud and Mbappe both break records as France reach World Cup quarters
France await the winner of England's World Cup last-16 clash with Senegal after strikers Olivier Giroud and Kylian Mbappe both broke scoring records in a comfortable 3-1 win over Poland.
The reigning World Cup champions claimed victory as Giroud made history by becoming France's all-time top goalscorer during the match at Al Thumama Stadium in Qatar.
World Cup 2022: Follow live updates from last-16 matches
Giroud entered the record books with 52 goals after hitting the back of the net at the end of the first half.
The 36-year-old previously drew level with fellow ex-Arsenal striker Thierry Henry – who held the record of 51 goals – after netting a double in France's 4-1 win against Australia in their opening Group D game.
Giroud (right) sticks his tongue out as France claim a second goal, scored by Mbappe
Mbappe scored the other two goals, becoming the first player to score eight – and then nine – World Cup goals before their 24th birthday.
His first of the night came in the second half at 73 minutes, before striking gold again in the 91st.
More on World Cup 2022
Poland's Robert Lewandowski clawed back a stoppage-time consolation from the penalty spot to end the game 3-1.
Now all eyes are on the Al Bayt Stadium as Group B winners England come face to face with Senegal for their first knockout match on the world stage since the agonising extra-time semi-final defeat to Croatia in 2018.
The game is set to kick off at 7pm GMT.
Of Course, Channing Tatum Got Asked About Salma Hayek's See-Through Dress At The Magic Mike 3 Premiere
The White Lotus' Michael Imperioli Gives Tour of His NYC Home
Did Benson & Stabler Finally Kiss on Law & Order: SVU? Find Out
GunFight Drops Heavy-Hitting Dubstep Single "Salvo"


text:
Q: Videoconference using Flash and SIP The front-end will be Flash, to run in a browser and have access to the camera.
I must use SIP to control the sessions.
How could I do this? Will a Red5 server and a MjSip sever do the trick? As in i'd use MjSip to setup the session and warn users about calls, and Red5 to stream the video and audio? Any suggestions?
Note: only 1-on-1 conference is required.

A: There are a couple of red5 related options to explore, the first one is an open source project called red5phone http://code.google.com/p/red5phone/
and the other is a more commercial type offering called OpenFire that you can read about here http://community.igniterealtime.org/blogs/ignite/2008/05/05/flashbased-audio-in-openfire-part-ii

redpajama_set_name: RedPajamaStackExchange


Similar to the Konfidence Float Jacket but offering a full swimwaer and floatation in one. With built in buoyancy to boost the wearer's natural buoyancy allowing the development of swimming technique while staying safe. The Konfidence Float Suit is designed with removable foam floats. These allow the buoyancy to be tailored to your childs needs and ability. Made of Licra fabric makes the suit super soft, stretchy and flexible for your childs comfortable. The float suits give parents and children confidence in and around water.


Posted on February 18, 2016 by Chris Eland. | Growth, Operations, People, Thoughts, Vision & Strategy.
Posted on January 14, 2016 by Chris Eland. | Operations, Vision & Strategy.
I love walking into an organization that needs some kind of assistance and hearing about their issues as perceived by the executive and staff.
Posted on December 15, 2015 by Chris Eland. | Growth, Operations, Vision & Strategy.


Genesis Medical Center, Davenport and Genesis Medical Center, Silvis have each been awarded "A" grades from Hospital Safety Score.
Hospital Safety Score is a quality and safety monitoring program of The Leapfrog Group (Leapfrog), an independent industry watchdog.
The Hospital Safety Score is calculated twice each year under the guidance of The Leapfrog Group's Blue Ribbon Expert Panel using publicly available data on patient injuries, medical and medication errors, and infections. U.S. hospitals were assigned an A, B, C, D, or F for their safety.
Hospital Safety Score uses 28 measures of publicly available hospital safety data to produce a single letter grade representing a hospital's overall capacity to keep patients safe from preventable harm. More than 2,500 general U.S. hospitals were assigned scores this fall. A full analysis of the data and methodology used is available at www.hospitalsafetyscore.org.
Genesis Health System, its affiliates and partners offer a full continuum of health care services for a 10-county region of Eastern Iowa and Western Illinois. Genesis hospital affiliates include: Acute and tertiary hospital care at Genesis Medical Center, Davenport and DeWitt, Iowa and at Genesis Medical Center, Silvis and Genesis Medical Center, Aledo, Ill. Genesis also manages a hospital in Maquoketa, Iowa. Genesis offers home health and hospice services through Genesis VNA and Hospice; Genesis Workplace Services; Clarissa C. Cook Hospice House; senior living facilities offering rehabilitation and long-term care; Genesis Health Group, with more nearly 170 primary care physicians and specialists; and, the Genesis Quad Cities Family Practice Residency program. For more information, visit our Web site at www.genesishealth.com.


text:
EXCLUSIVE: Wil Wheaton Talks COPD Social Media Initiative, Leonard Nimoy
Kyle Hadyniak
Wil Wheaton Interview – Part I: Former Star Trek: The Next Generation actor Wil Wheaton talks #BreatheBoldly, Leonard Nimoy and more
TrekNews.net recently had the opportunity to sit down with Wil Wheaton (Wesley Crusher from Star Trek: The Next Generation) and talk about his involvement in the "BreatheBoldly" social media campaign, a drive to raise awareness for Chronic Obstructive Pulmonary Disease (COPD). COPD is a disease that claims 3 million people each year, including the life of Star Trek legend Leonard Nimoy in February 2015.
The campaign includes celebrities such as Whoopi Goldberg, Mario Lopez, Cindy Crawford, and Kyle Richards, just to name a few. Wheaton joined the initiative not only in remembrance of Nimoy, but because COPD is a commonly misunderstood and relatively unknown disease despite its prevalence as a leading cause of death. Wheaton admitted that he was one of those who knew very little of the disease before Nimoy's death and this year's campaign.
Wheaton as Wesley Crusher on Star Trek: The Next Generation (photo: CBS Home Entertainment)
"I didn't know Leonard had COPD at all," said Wheaton. "In fact, one of the reasons why I agreed to do this campaign, was that I knew absolutely nothing about COPD. I didn't know he was effected by it in any way. Another reason why I really wanted to get involved with this campaign and talk about it so people can become aware of it, is that if someone of Leonard Nimoy's stature, reputation, career, and fame can suffer and die from this disease, why does nobody know about it? Especially when you find out it is a leading cause of death in America. I had no idea. Just by talking about it makes it more likely that someone who is in the early stages of COPD will seek treatment and have a good quality of life. As a society, we need to work on finding a cure for this."
Wheaton actually didn't have as close a relationship with Nimoy as some of his TNG cast mates, but from his limited interactions with Nimoy, the older actor did nothing but exude kindness and wisdom.
Nimoy as Spock in 2009's Star Trek (photo: Paramount Pictures)
"I only worked with him a couple of times during the years that we were on the show, and my relationship with him was probably closer to the relationship that the average Star Trek fan has," explained Wheaton. "I had the incredible fortune to get to sit down and talk to him a couple of times. And those few times we were actually in the same place together, I was just so intimidated, not by anything he said, or did, but just by his existence. So that basically sums up the relationship we had. The few times we did interact one on one, he was fantastically kind and he was one of those people that had no reason to indulge me, there was no reason for him to tolerate this nerdy dude. He did anyway. There are people who are involved in things like Star Trek, we know what it means to people. Some of us respect that, and we honor it, and there are some people who don't. And he was certainly one of the people who did."
#BreatheBoldly, launched by Philips, a Dutch healthcare technology company, asks participants to take a "straw selfie." In other words, people who join the campaign are asked to post a selfie of themselves doing a moderately physical activity, while only breathing through a straw. This is designed to replicate the breathing difficulties those with COPD experience every day. For Wheaton, this meant trying to run while only breathing through a straw.
"I run almost every day, and I tried running with a straw," explained Wheaton. "I usually run for 30-40 minutes without stopping when I'm out doing my training runs. I think I made it almost a full block with the straw, because I just couldn't do it. And I'm young and healthy. Just imagine what's it's like for someone who doesn't have that good fortune.
Wheaton encourages people to try the straw selfie for themselves, in whatever way they can.
"Grab a drinking straw and try to do something moderately strenuous, and don't cheat," said Wheaton. "You can't breathe through your nose. Try to do some jumping jacks, or go up and down some stairs. Think about what it means for someone to not be able breathe. That is terrifying."
For more information on #BreatheBoldly, visit Philips.
You can follow Wil Wheaton on Twitter at @wilw.
Visit TrekNews.net tomorrow to read the second part of our exclusive interview with Wil Wheaton as he talks Star Trek: Discovery, the Wesley Crusher character and his time on Star Trek: The Next Generation.
In this article:Star Trek: The Next Generation, Wil Wheaton
Written By Kyle Hadyniak
Kyle Hadyniak has been a lifelong Star Trek fan, and isn't ashamed to admit that Star Trek V: The Final Frontier and Star Trek: Nemesis are his favorite Star Trek movies. You can follow Kyle on Twitter @khady93.
Talos4
I'm not a big fan of Wheaton's politics, but I applaud him for doing this, of course. Raising awareness of a little-known but serious ailment is always a good thing.
Suzy Garrison
As a copd patient I want to thank Wil Wheaton for doing this. The website has helped me understand what I am going through. It has eased some of my fears and increased my understanding.
Follow @TrekNewsNet
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Who killed Yasser Arafat? When the Palestinian leader was declared dead in a French hospital on Nov. 11, 2004, there was no way of knowing how questions related to his death should be phrased. Was he killed or did he die from old age? If he was killed, then who killed him and why? The "mysterious" nature of his symptoms gave birth to a theory that he was poisoned over a period of time, provided enough evidence that foul play was involved, even accusing some of those closest to him. Although the man's story has been recorded in the ever-growing chronicle of the Palestinian struggle and Palestinians have somehow moved on, recent breaking news has blown his story wide open once again, breeding new controversy and stories of conspiracy.
Nearly five years have passed since Arafat died. During those years, a number of high-ranking Palestinian leaders, especially from the Hamas movement, have been assassinated by Israel in various and consistently gory methods. Among Palestinians, Arafat is referred to like all those killed by Israel, as a "martyr", an indication of the widespread belief that his death was hardly the result of natural causes.
If Arafat was indeed killed and since his death was not caused by an Israeli airstrike or an assassin's bullet, a key question has been lingering, giving rise to all sorts of answers — who killed Arafat and how?
Israelis made little secret of their desire to see Arafat dead. Former Israeli Prime Minister Ariel Sharon expressed regret in a newspaper interview on Feb. 1, 2002 that he hadn't killed Arafat decades earlier when he had had the chance. Sharon told Israeli newspaper Maariv that he should have "eliminated" Arafat during the invasion of Lebanon in 1982. "Do you regret it (not killing Arafat)?" he was asked. "Certainly, yes," he replied.
On the day of Arafat's death, BBC news carried comments by then Israeli opposition leader Shimon Peres, saying it is "good that the world is rid of him...The sun is shining in the Middle East." Held hostage in his bullet-riddled West Bank office for years, Arafat represented an international embarrassment for Israel. He was not "moderate" enough to concede all Palestinian rights, but 'moderate' enough to maintain an aura of international attention and support among Arab, Muslim, European and other nations.
Still, in the minds of some, Arafat was determined, and often declared to represent an 'obstacle'. The PA's truly "moderate" camp disliked him for his tireless compromises aimed at preventing factional infighting, thus blocking their attempts at dominating Palestinian society. Israel despised him for numerous reasons, not least his refusal to "concede" issues of paramount importance, such as refugees and Jerusalem. The Bush administration took every opportunity to discredit, discount and insult him, constantly propping up an "alternative" leadership, namely, Mahmoud Abbas, Mohammed Dahlan and others.
Strangely enough, even Abbas and other high-ranking PA officials refer to Arafat as a "martyr," especially whenever they need to capitalize on his legacy among low-ranking Fatah members and ordinary Palestinians. But the story was meant to end here, with Abbas and Dahlan, carrying the torch of Arafat the "martyr" as they continue with their rhetoric-based "revolution" to liberate Palestine. That was the case until the second highest-ranking Fatah member and one of the PLO's most visible leaders, Farouk Qaddoumi, went public with a document that contained some unanticipated surprises: that Abbas and Dahlan, along with Sharon, US Undersecretary of State William Burns, and others jointly plotted the assassination of Arafat. Qaddoumi's document contained the minutes of that meeting, in 2004.
Qaddoumi broke the news in a press conference in Amman, Jordan on July 12, 2009, asserting that Arafat had entrusted him with the minutes of that secret meeting involving top Israeli, Palestinian and American leaders and officials. The plot, according to Qaddoumi included the assassination of other Palestinian leaders, some of them have indeed been assassinated since while others are still alive, thanks to the failure of Israeli missiles and car bombs.
Expectedly, the Ramallah-based Fatah leaders launched fierce verbal attacks against Qaddoumi, questioning his objectives, timing and even his sanity. Abbas accused Qaddoumi of wanting to torpedo the Fatah faction's long-delayed congress, scheduled to convene in Bethlehem on Aug. 4. "He (Qaddoumi) knows full well that this information is false; he has released it to undermine the convention but we are continuing with the preparations," Abbas said. Qaddoumi had in fact criticized the convention of a supposedly 'revolutionary' movement held with Israeli consent, if not support.
The fact is, we may never know the authenticity of Qaddoumi's report without an independent investigation or irrefutable evidence. However, just as with Arafat's death, conclusive evidence is not always required for the public to formulate an opinion. Considering Israel's threats to Arafat, Palestinians have no reason to believe that Israel did not kill him. Similarly, ordinary Palestinians, especially those in Gaza, have little reason to trust that corrupt Palestinians were not involved in Arafat's death. A clique of the Palestinian elite have made it clear that their personal interests surpass those of the Palestinian people; Dahlan openly advocated the toppling of an elected government in Gaza as the Ramallah-based "revolutionary" movement, was dispatching US-armed and trained Palestinian fighters to crack down on Israel's enemies in various West Bank towns.
As bizarre as all of this may sound, it is at least enough to explain why Palestinians are willing to believe the recent statements made by Qaddoumi, a respected figure among all Palestinian factions. True, Qaddoumi's accusations have yet to be authenticated by an independent investigation, but they are made in a fractious, if not peculiar political context that makes them most plausible and, in a sense, that is the real tragedy.


text:
Las lenguas del sur de Vanuatu es un subgrupo de las lenguas oceánicas meridionales. Agrupa a nueve idiomas.

Clasificación
Según la obra Ethnologue, este subgrupo de lenguas está integrado por:
Aneityum
Lenguas erromanga
Sie
Ifo
Ura
Lenguas tanna
Kwamera
Lenakel
Tanna del norte
Tanna del sudoeste
Whitesands

Comparación léxica
Los numerales del 1 al 10 en diferentes ramas de lenguas de Vanuatu meridional son:

Los términos entre paréntesis son préstamos del inglés.

Referencias

Vanuatu meridional
Meridional

redpajama_set_name: RedPajamaWikipedia