Researchers at the Cockrell School of Engineering at the University of Texas at Austin have developed a self-healing gel that repairs and connects electronic circuits. The innovation could create opportunities to advance the development of flexible electronics, biosensors and batteries as energy storage devices.
Although technology is moving toward lighter, flexible, foldable and rollable electronics, the existing circuits that power them are not built to flex freely and self-repair cracks or breaks that occur. Self-healing materials that have been developed to date have relied on application of external stimuli such as light or heat to activate repair.
A team led by Assistant Professor of Mechanical Engineering Guihua Yu has now created a “supergel” material with high conductivity and strong mechanical and electrical self-healing properties that does not require heat or light to fix a crack or break in a circuit or battery. The team did this by combining two gels: a polymer hydrogel that is a conductor and a self-assembling metal-ligand gel that provides self-healing properties.
Using a disc-shaped liquid crystal molecule to enhance the conductivity, biocompatibility and permeability of their polymer hydrogel, the researchers achieved about 10 times the conductivity of other polymer hydrogels used in bioelectronics and conventional rechargeable batteries. The nanostructures that make up the gel are among the smallest structures capable of providing efficient charge and energy transport.
The second ingredient of the self-healing hybrid gel—a metal-ligand supramolecular gel—uses terpyridine molecules to create the framework and zinc atoms as a structural glue. This allows the molecules to form structures that are able to self-assemble and give it the ability to automatically heal after a break. When the supramolecular gel is introduced into the polymer hydrogel and forms the hybrid gel, its mechanical strength and elasticity are enhanced.
To construct the self-healing electronic circuit, Yu says that the self-healing gel would not replace the typical metal conductors that transport electricity, but instead be used as a soft joint to join 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 says. “One day, you could glue or paste the gel to these junctions so that the circuits could be more robust and harder to break.”
Yu’s team is also looking into other uses for the gel, including medical applications and energy storage, where it could potentially be used within batteries.