Design and functional evaluation of an epidermal strain sensing system for hand tracking

Abstract

This study demonstrates soft, epidermal resistive strain gauges capable of tracking finger joint angle during dexterous manipulation tasks. Intrinsically stretchable, biphasic, gallium-based metal films embedded in an elastomeric substrate allow for extremely thin (<50 µm) and skin-conforming wearable sensors with outstanding robustness. The sensors sustain repeated cycling to 50% strain and are insensitive to normal pressure up to 100 kPa. Following a calibration phase, we recorded flexions of a human finger using the soft sensors and compared their joint angle estimation to that of a commercial marker-based visual motion tracking system. The accuracy of our system (defined as the mean angular deviation between our sensors' output and the reference system) was below 9° over a set of 11 different grasping and motion tasks. We demonstrate the scalability and wearability of our technology with a three-finger sensing system used to track the fine movements of a pianist hand. Our soft technology is a promising candidate for implementation of truly wearable proprioceptive sensing systems.