Multimodal sensor for soft grippers based on optical displacement sensing

Abstract

Soft grippers enable to securely grasp objects of various shapes without complex control algorithms. However, the nature of the soft material presents a challenge regarding the attachment of sensors to the fingers, hindering the ability to obtain feedback data on their current state. This study introduces a novel sensor concept designed to be affixed to the fingers of a soft gripper, enabling the measurement of both bending angles and contact forces. The proposed sensor utilizes photo-reflectors to simultaneously measure bending angles and contact forces at multiple points, with the capability to easily expand the number of measurable cells. To enhance durability, a flexible printed circuit board with proven durability, along with a slip mechanism structure, is incorporated. Through the experiments, the feasibility of the proposed sensor is validated. Also, the durability and long-term repeatability of the sensor was verified through 100,000 repeated operations. © 2025 The Author(s). Electronics Letters published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.