Scientists have fabricated a flexible electrical circuit that, when cut into two pieces, can repair itself and fully restore its original conductivity. The circuit is made of a new gel that possesses a combination of properties that are not typically seen together: high conductivity, flexibility, and room-temperature self-healing. The gel could potentially offer self-healing for a variety of applications, including flexible electronics, soft robotics, artificial skins, biomimetic prostheses, and energy storage devices. The researchers, led by Guihua Yu, an assistant professor at the University of Texas at Austin, have published a paper on the new self-healing gel in a recent issue of Nano Letters.
The new gel’s properties arise from its hybrid composition of two gels: a supramolecular gel, or ‘supergel’, is injected into a conductive polymer hydrogel matrix. As the researchers explain, this “guest-to-host” strategy allows the chemical and physical features of each component to be combined. The supergel, or the “guest,” provides the self-healing ability due to its supramolecular chemistry. As a supramolecular assembly, it consists of large molecular subunits rather than individual molecules. Due to its large size and structure, the assembly is held together by much weaker interactions than normal molecules, and these interactions can also be reversible. This reversibility is what gives the supergel its ability to act like a “dynamic glue” and reassemble itself. Meanwhile, the conductive polymer hydrogel, or the “host,” contributes to the conductivity due to its nanostructured 3D network that promotes electron transport. As the backbone of the hybrid gel, the hydrogel component also reinforces its strength and elasticity. When the supergel is injected into the hydrogel matrix, it wraps around the hydrogel in such a way as to form a second network, further strengthening the hybrid gel as a whole.