New self-healing gel could lead to flexible electronics

Scientists have developed a first-of-its-kind self-healing gel that could repair and connect electronic circuits, an advance that could lead to next-generation of flexible electronics.
Although technology is moving towards lighter, flexible, foldable and rollable electronics, the existing circuits that power them are not built to flex freely and repeatedly self-repair cracks or breaks that can happen from normal wear and tear.
Until now, self-healing materials have relied on application of external stimuli such as light or heat to activate repair.
The new "supergel" material developed by researchers from University of Texas at Austin has high conductivity and strong mechanical and electrical self-healing properties.

"There's no need for heat or light to fix the crack or break in a circuit or battery, which is often required by previously developed self-healing materials," said assistant professor Guihua Yu, who developed the gel.
The researchers created the self-healing gel by combining a self-assembling metal-ligand gel that provides self-healing properties and a polymer hydrogel that is a conductor.

The researchers used a disc-shaped liquid crystal molecule to enhance the conductivity, biocompatibility and permeability of their polymer hydrogel.
They were able to achieve about 10 times the conductivity of other polymer hydrogels used in bioelectronics and conventional rechargeable batteries.

The nanostructures that make up the gel are the smallest structures capable of providing efficient charge and energy transport, the researchers said.
In a separate study, Yu introduced the self-healing hybrid gel. The second ingredient of the self-healing hybrid gel is a metal-ligand supramolecular gel.
Using terpyridine molecules to create the framework and zinc atoms as a structural glue, the molecules form structures that are able to self-assemble, giving it the ability to automatically heal after a break.
When the supramolecular gel is introduced into the polymer hydrogel, forming the hybrid gel, its mechanical strength and elasticity are enhanced.
To construct the self-healing electronic circuit, the self-healing gel could be used as a soft joint, joining other parts of the circuit.

"This gel can be applied at the circuit's junction points because that's often where you see the breakage," he said.
"One day, you could glue or paste the gel to these junctions so that the circuits could be more robust and harder to break," he said.
The research was published in the journal Nano Letters.