Stretching and Twisting Sensing With Liquid-Metal Strain Gauges Printed on Silicone Elastomers

This letter reports ultra-stretchable strain gauges based on a liquid metal (eutectic gallium-indium) and a platinum-catalyzed silicone elastomer (EcoFlex). A custom liquid metal printing setup was constructed and operated in the pressure controlled mode to offer high quality printing by eliminating undulation typically encountered in the flow rate control mode via a syringe pump. Printed liquid-metal strain gauges were thoroughly tested under cyclic uniaxial stretching and twisting. We achieved the stretchability of similar to 700%, which can cover any high strain from human motion. In case of moderate strain of 350%, our liquid-metal strain gauge could be operated more than 4500 cycles without showing any degradation.