Using a new gel, which contains properties seldom seen together – high conductivity, flexibility and room temperature self-healing – a group of US scientists have developed an electrical circuit that can repair itself and restore normal functioning even after being cut in two.
A paper presenting the gel, hoped to eventually confer self-healing properties to a variety of applications, including flexible electronics, soft robotics, artificial skins, biomimetic prostheses, and energy storage devices, was published in a recent issue of Nano Letters.
This fascinating new material is actually a combination of two gels – a supramolecular gel, or “supergel”, that’s been injected into a conductive polymer hydrogel matrix.
The “supergel” is a supramolecular assembly, which consists of large molecular subunits rather than individual molecules. Due to its large size and structure, it 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 hydrogel (or the “host”) is a nano-structured 3D network that promotes electron transport, providing the hybrid gel with conductivity and elasticity, as well as acting as a “backbone” for the “supergel” to wrap around and strengthen the resulting material as a whole.
Tests performed on thin films of the hybrid gel on flexible plastic substrates revealed high conductivity (as high it gets for this type of substrate), which is maintained after continuous bending and stretching – all thanks to the gel’s self-healing properties.
Most interestingly, however, the team also performed experiments on an electrical circuit made from the hybrid gel, showing its ability to self-repair and restore normal functioning even after being cut in the same place several times in a row. The healing takes only about a minute.
Project leader Guihua Yu, an Assistant Professor at the University of Texas, Austin, commented on the varied potential uses the new gel could be applied to in near future. “For example, the gel can be potentially used in implantable biosensors as flexible yet self-healable electrodes, ensuring the durability of these devices. And in energy devices, for example, the gel can function as binder materials for advanced battery electrodes in high-density Li-ion batteries where high-capacity electrodes may experience substantial volume changes.”
The researchers also hope that, by combining supramolecular chemistry and polymer nanoscience, the resulting hybrid gels may provide a useful strategy for designing new self-healing substrates. According to Yu, a better understanding of the mechanisms behind the self-healing properties of hybrid gels could lead to better materials down the road.
As for practical applications, there are already plans to direct research efforts to develop scalable synthetic strategies of supramolecules and self-healing hybrid gels with even better mechanical strength and elasticity “for potential applications of these self-healing gels in different technology areas”.