An Electronic Skin Strain Sensor for Adaptive Angle Calculation

Electronic skin (e-skin) with excellent flexibility and comfortable wearability has attracted considerable attention in the past decade. Flexible strain sensors are one of the key elements of e-skins, which are always attached to the joints of humans or robots for motion monitoring. However, most strain sensors previously reported cannot fit different joints to measure the bending angles without calibration. This work aims to propose a flexible strain sensor with an adaptive model for automatically calculating the bending angle of different joints. The proposed sensor is a screen-printed liquid metal strain sensor with a size of 120 mm (L)
$\times20$
mm (W)
$\times 400\mu $
m (H). The real-time changes in different curvatures as the sensor bend has been investigated. Based on the curvature-strain-bending angle relationship of different joints, we use the Gaussian function to model the bending angle solution for adaptive curvature. Experimental results show that the proposed sensor can be served as the electronic skin on the joint’s surface to measure the bending angle adaptively, which provides a promising path for adaptive motion monitoring in human movement, soft robotics, prosthetic devices, etc.