Back in February, we talked about how Switzerland’s EPFL scientists contrived reconfigurable and self-repairing electronic circuits. Well, this time around, a team of researchers (headed by by Guihua Yu, an assistant professor) at the University of Texas, have created their version of a self-healing electrical circuit. Demonstrating its intrinsic flexibility, the circuit can not only repair itself, but also restore its conductivity – even when broken into two pieces. Such special attributes are showcased by virtue of the pliant gel material of the circuit – which combines a host of seemingly contrasting properties, including high conductivity and a healing factor that is activated even in room temperatures.
As for the composition of the circuit gel in question, the hybrid material actually consists of two separate gels that are combined into a singular scope. To that end, the scientists successfully managed to inject a ‘guest’ supramolecular gel (or ‘supergel’) into the ‘host’ matrix of a conductive polymer hydrogel. This ‘guest’ supramolecular gel accounts for the self-healing features of the circuit, since it already boasts of larger molecular sub-units. From the chemical perspective, the larger molecular structures allow for weaker interactions (when compared to conventional molecules), and these interactions can also be made reversible. It is this latter property of reversibility which endows the supramolecular gel with glue-like, self assembling ‘powers’.
On the other hand, the ‘host’ polymer hydrogel enhances the conductivity of the circuit – with the aid of its three-dimensional nanostructure that complements flow of electrons. Moreover, the hydrogel is also known for its innate state of flexibility. This advantage when combined with the injection of the supergel (that ‘wraps’ around the hydrogel), endows the resultant hybrid gel with both strength and pliancy.
Now, coming to the experiment phase, the researchers tested out their contrivance by placing thin films of this hybrid gel on flexible plastic substrates (‘wafers’). The results were pretty encouraging with the conductivity figures being among the highest ever achieved in (conductive) hybrid gels. More importantly, the conductive magnitude was maintained even after repeated alteration of the material’s shape (with bending and stretching) – due to the self-healing attribute of the gel. In fact, the researchers found out that the electrical circuit (after being cut into two pieces) could self-heal and restore its original conductivity within just a minute.
Suffice it to say, such electrical circuits can potentially have a myriad applications in future technologies. As Yu explained (to Phys) –
The conductive self-healing gel we developed can be applied in many technological areas, from flexible/stretchable electronics, artificial skins, energy storage and conversion devices, to biomedical devices. 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.
Lastly, as for the practical development of the hybrid gel circuit, the scientists want to further assess the fundamental nature of the self-healing properties of supergels and their related chemical interactions. And, the good news is, the researchers are also looking forth to contrive ‘better’ versions of such gels with greater strength and flexibility – thus alluding to the possibility of commercial manufacturing in the near future.
The study was originally published in the Nano Letters journal.