Touch, press and stroke: a soft capacitive sensor skin

TL;DR

This paper introduces a soft capacitive sensor skin capable of detecting shear, normal force, and proximity, with potential applications in humanoid robotics for safe and precise physical interactions.

Contribution

A novel capacitive sensor design with patterned elastomer and sliding pillars that can differentiate pressure, shear, and proximity, fabricated through a straightforward method.

Findings

Detects finger proximity up to 15 mm

Differentiates pressure and shear forces effectively

Demonstrated on a robotic gripper handling a cup

Abstract

Soft sensors that can discriminate shear and normal force could help provide machines the fine control desirable for safe and effective physical interactions with people. A capacitive sensor is made for this purpose, composed of patterned elastomer and containing both fixed and sliding pillars that allow the sensor to deform and buckle, much like skin itself. The sensor differentiates between simultaneously applied pressure and shear. In addition, finger proximity is detectable up to 15 mm, with a pressure and shear sensitivity of 1 kPa and a displacement resolution of 50 $\mu$m. The operation is demonstrated on a simple gripper holding a cup. The combination of features and the straightforward fabrication method make this sensor a candidate for implementation as a sensing skin for humanoid robotics applications.