Flexible and highly sensitive ionic skins with multiple dielectric layers for finger joint bending angle monitoring

Abstract

Finger joint motion monitoring is crucial for rehabilitation training and ergonomics. Based on a multilayer dielectric structure, this study proposed flexible and highly sensitive ionic skins (sensors) for the measurement of the bending angles of finger joints. Each ionic skin, consisting silicon rubber films (multiple dielectric layers) and highly stretchable ionic conductors, was attached to the finger joint surface. The capacitance change of the skin was captured and used to measure finger joint bending angles. On this basis, the relationship between angles and capacitance variations was established. The relationship agreed with the experimental results. Furthermore, the effect of number of dielectric layers on sensitivity and linearity was discussed. The experimental results indicated that an increase in the number of dielectric layers improved sensitivity but suppressed linearity. The proposed ionic skins provided higher sensitivity and linearity than other flexible sensors. The five-layer ionic skin was four times more sensitive than existing ionic skins. The results confirmed that the multilayer dielectric structure of our ionic skins substantially enhanced the sensitivity for finger joint bending angle measurements.