Stretchable, Conductive Touch Sensors for Wearable Electronics

North Carolina State University engineers have created conductive and stretchable wires that can sense twisting, strain, and touch. These soft, microscopic fibers could be useful for integrating electronics in wearable devices. Each fiber consists of three strands filled with a liquid metal alloy. One is completely filled with eutectic gallium and indium (EGaIn), one is two-thirds filled with EGaIn, and one is only one-third filled with EGaIn. The slim tubes are then twisted together into a tight spiral. Increasing the number of twists elongates the elastic strands and brings the EGaIn in the two tubes closer together, which changes the capacitance between the two strands. This video demonstrates the mode of sensing in which the metal inside the fibers detects touch via changes in capacitance. As a finger touches each region of the fiber, a different LED lights up. Touchscreens on smartphones and tablets utilize similar principles.