Materials: ‘Super jelly’ made of 80 percent water can survive being run over by a CAR
Is it a bird? Is it a plane? No, it’s “super jelly” – a bizarre new material that can survive a car run over, even though it’s 80 percent water.
The “vitreous hydrogel” looks and feels like a squishy jelly, but when compressed it acts like shatterproof glass, the developers at the University of Cambridge said.
It is formed using a network of polymers held together by a series of reversible chemical interactions that can be modified to control the mechanical properties of the gel.
This is the first time a soft material capable of such significant resistance to compressive forces has been produced.
Superjellies could find a variety of uses, the team added, from use for building soft robotics and bioelectronics to replacing damaged cartilage.
The team has already used their new material to create a hydrogel pressure sensor, which, when placed under the foot, can track subjects walking, standing and jumping.
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Is it a bird? Is it a plane? No, it’s “super jelly” – a bizarre new material that can survive a car run over, even though it’s 80 percent water. Pictured: the vitreous hydrogel
What are hydrogels?
Hydrogels are three-dimensional networks of cross-linked, ‘hydrophilic’ (water-loving) polymers.
They do not dissolve in water and instead are highly absorbent, but able to maintain well-defined structures.
While most hydrogels are of synthetic origin, some are naturally derived.
They can be used for a variety of applications, from soft robotics and contact lenses to tissue repair scaffolds and disposable diapers.
Hydrogels are three-dimensional networks of ‘hydrophilic’ (water-loving) polymers that swell in water and can hold a large amount of liquid while retaining their structure.
The toughness and self-healing ability of hydrogels have made them a popular research topic in recent years. However, it has proved challenging to make one that can withstand compression without being crushed.
“To make materials with the mechanical properties we want, we use crosslinkers, where two molecules are linked through a chemical bond,” says the paper’s author and synthetic polymer chemist at the University of Cambridge, Zehuan Huang.
“We use reversible crosslinkers to make soft and stretchable hydrogels, but making a hard and compressible hydrogel is difficult and designing a material with these properties is completely counterintuitive.”
The key to the superjelly lies in barrel-shaped molecules called cucurbituriles, which are cross-linking molecules that can hold two guest molecules in their cavity in a way the researchers compare to a handcuff.
By selecting guest molecules that prefer to stay in these handcuffs longer than usual, the team was able to keep the polymer network tightly connected and make it resistant to significant amounts of compression.
“With a water content of 80 percent, you’d think it would burst like a water balloon, but it doesn’t: it stays intact and withstands enormous compressive forces,” says author and polymer chemist Oren Scherman, also of the university. from Cambridge.
‘The properties of the hydrogel seem to be at odds with each other.’
“The way the hydrogel can withstand compression was surprising, it wasn’t like anything we’ve seen in hydrogels,” added paper co-author Jade McCune.
‘We also found that compressive strength could be easily controlled by simply changing the chemical structure of the host molecule in the handcuff.’
The “vitreous hydrogel” looks and feels like a squishy jelly, but when compressed it acts like shatterproof glass, the developers at the University of Cambridge said. Pictured: After being run over by a car repeatedly, the ‘vitreous hydrogel’ returned to its original shape
The team explained that the application of different guest molecules allowed for significant variation in the dynamics of the resulting material.
‘People have spent years making rubbery hydrogels, but that’s only half the picture,’ says Professor Scherman.
“We’ve revisited traditional polymer physics and created a new class of materials that spans the range of material properties, from rubbery to glassy, completing the full picture.”
Dr Huang added: ‘To our knowledge, this is the first time glass-like hydrogels have been created.
‘Not only are we writing something new in the textbooks, which is very exciting, but we are opening a new chapter in the field of high-quality soft materials.’
The study’s full findings were published in the journal Natural materials.
SOFT ROBOTS: SCIENTISTS CREATE SKIN THAT REPAIRS ITSELF
Cutting your hand, tearing a muscle, or even breaking a bone are all injuries that heal over time.
Experts from the Vrije Universiteit Brussel (VUB) have created a synthetic skin that aims to mimic nature’s self-healing ability, allowing robots to recover from ‘wounds’ they incur while performing their tasks.
Further development of the technology could also allow Terminator-style killer robots built for the battlefield to repair the damage they take in combat.
Researchers have been experimenting with soft robots for some time.
They are made of flexible materials, inspired by the soft tissue from which humans and many other organisms are made.
Their flexibility allows them to be used for a wide variety of applications, from gripping delicate and soft objects in the food industry to performing minimally invasive surgery.
They can also play an important role in creating lifelike prosthetics.
However, the soft materials also make them susceptible to damage from sharp objects or excessive pressure.
Damaged parts must then be replaced to prevent the robot from ending up in the scrap heap.
But the VUB has devised a new rubber polymer that can repair this type of damage.
Professor Bram Vanderborght of BruBotics VUB, who worked on the plastic, said: ‘The outcome of the research opens up promising perspectives.
“Not only can robots be made lighter and safer, they will also be able to work independently for longer without the need for constant repairs.”
To make their synthetic meats, the scientists used jelly-like polymers that melt together when heated and then cooled.
When damaged, these materials first recover their original shape and then heal completely.
This principle was applied in three self-healing robot components; a gripper, a robotic hand and an artificial muscle.
These resilient pneumatic components were damaged under controlled conditions to test whether the scientific principle works in practice