Stretchable Helical Wire Made with Liquid Metal

In this study, a stretchable liquid metal (Galinstan) wire was formed into a three-dimensional coil to prevent resistance change during device deformation. The technique was based on core-shell hydrogel microsprings previously fabricated using a double bevel-tip nozzle. In this study, conductive Galinstan was injected into the microspring core to replace the starch with which it was initially formed. In stretchable and flexible electronics, it is crucial to prevent changes in the electrical parameters, in particular direct current resistance and alternating current (AC) impedance, during device deformation. The developed metal wire maintained stable resistance (less than 1.2% change) during 100% tension and stable impedance (less than 0.2% change) from 1 to 100 kHz AC. As a result, we realized a liquid metal wire that has high electrical stability during deformation. This development represents an important advance towards the realization of "liquid-state" electronic systems.