A Stretchable Filament Sensor with Tunable Sensitivity for Wearable Robotics and Healthcare Applications

Taking a leaf out of evolutionary biology, soft robots have begun to utilize compliant materials and structures for improved interactions with humans and complex environments. However, these advances have not been followed closely by sensing mechanisms. Biology has had a head start on the development of advanced sensing systems. The human body and its skeletal muscles can tune their morphologies to interact with the surrounding environment. Inspired by such biological systems, this paper introduces a novel hydraulic soft filament sensor (SFS) with tunable sensitivity. The SFS is a type of hydraulic pressure-based tubular strain sensor, which has a sensing core made of a soft and stretchable micro-sized filament filled with incompressible fluid where its inner hydraulic pressure is changed with strain. The SFS can be customized to form a wide range of configurations such as a long fiber or a skin-like structure. To demonstrate the SFS capability, different configurations for the SFS are fabricated and experimentally validated. The scalable and tunable nature of the SFS makes it suitable for a wide range of wearable and medical applications.