Highly Stretchable and Transparent Microfluidic Strain Sensors for Monitoring Human Body Motions

TLDR

We present a new class of simple, highly stretchable, transparent microfluidic strain sensors that combine microfluidic techniques with ionic liquids to achieve high sensitivity, long‑term stability, and fast response to diverse deformations. The sensors are fabricated by embedding refractive‑index matched ionic liquids into microfluidic channels within an elastomeric matrix, and their operation is governed by a theoretical model of elastic channel deformation, enabling demonstration on finger, wrist, and arm. The sensors exhibit outstanding performance under stretching, bending, pressing, and twisting, successfully monitor diverse human body motions in real time, and hold promise for future stretchable electronic devices.

Abstract

We report a new class of simple microfluidic strain sensors with high stretchability, transparency, sensitivity, and long-term stability with no considerable hysteresis and a fast response to various deformations by combining the merits of microfluidic techniques and ionic liquids. The high optical transparency of the strain sensors was achieved by introducing refractive-index matched ionic liquids into microfluidic networks or channels embedded in an elastomeric matrix. The microfluidic strain sensors offer the outstanding sensor performance under a variety of deformations induced by stretching, bending, pressing, and twisting of the microfluidic strain sensors. The principle of our microfluidic strain sensor is explained by a theoretical model based on the elastic channel deformation. In order to demonstrate its capability of practical usage, the simple-structured microfluidic strain sensors were performed onto a finger, wrist, and arm. The highly stretchable and transparent microfluidic strain sensors were successfully applied as potential platforms for distinctively monitoring a wide range of human body motions in real time. Our novel microfluidic strain sensors show great promise for making future stretchable electronic devices.