Highly stretchable liquid-metal based strain sensor with high sensitivity for human activity monitoring

Sensors with high sensitivity, a wide detection range, large stretchability and skin-like elastic compliance are highly desirable for biomedical applications. Liquid metal (LM)-based composites, characterized by being highly stretchable and mechanically compatible to biological tissues, have great potential for stretchable wearable sensors, but they are limited to relatively small resistive changes with the applied stretch. Here we report a highly stretchable, conformable and highly sensitive strain sensor fabricated by inserting putty-like conductive mixture composed of SiO₂ microspheres and LM into elastomer microchannels. The introduction of the SiO₂ microspheres effectively improves the sensitivity of the sensor while retaining the desirable mechanical properties. The capture of various human activities, such as different states of mouth, finger, hand and elbow, has been demonstrated by using the prepared sensor and a wireless sensory system.