Jul 11, 2012
Nanoparticle film senses strain with high sensitivity
Strain gauges provide the basis for a wide variety of transducers such as pressure sensors, weighing scales and accelerometers. Currently, strain gauges of high sensitivity are made from silicon using CMOS technology. Stain gauges made from metals exhibit a sensitivity of at least one order of magnitude smaller than their silicon rivals, but they easier to fabricate and of lower cost.
Researchers in Greece have been working on techniques to make nanoparticles in vacuum and studying self-organization phenomena. In parallel the team based at the National Technical University of Athens has been investigating possible applications of nanoparticles in the field of sensors and electronic memories.
Modified magnetron sputtering
The group uses a modified magnetron sputtering process to produce its nanoparticles, which are deposited between metallic electrodes. The nanoparticle source consists of a magnetron that attracts an ionized argon gas, sputtering the target material. The argon gas flow rate and distance travelled through an aggregation zone can be adjusted to produce nanoparticles of a controllable size on a target substrate. The aerial density of nanoparticles is proportional to the deposition time. For long deposition times the density of nanoparticles is so high that they are touching one another exhibiting a low resistance film.
The measured resistance of the device is strongly influenced by the inter-particle distance, which varies with density and sample straining. In the study, the aerial density was correlated with the resistance value using TEM to observe the nanoparticles.
Order of magnitude higher
An intermediate nanoparticle density was found to produce devices with greater sensitivity. Using these tailored films, the team produced strain sensing devices with a sensitivity that is more than an order of magnitude higher than that of continuous metallic films.
Future plans include demonstrating the technique on MEMS structures and also on flexible substrates for low-cost applications.
More information can be found in the journal Nanotechnology.
About the author
The work was performed in the Department of Applied Physics at the National Technical University of Athens by researchers from the Electronic Nanomaterials and Devices group led by Prof. Dimitris Tsoukalas and within the framework of the Marie-Curie Nanosource project that allowed Dr Joseph Tanner to perform a postdoctoral work in the lab collaborating with Dimitris Mousadakos who was working on his Master’s thesis and Evangelos Skotadis who is preparing his PhD. Dr Kostas Giannakopoulos performed the electron microscopy analysis at the Demokritos Research Center.