Stretchable Strain Sensor Based on Areal Change of Carbon Nanotube Electrode

Abstract

Conventional strain sensors measure strains exerted on solid metals and have been widely applied. Stretch measurements of flexible objects require strain sensors with wide dynamic range (stretch exceeding 100%) that can also measure areal changes. Flexible strain sensors are expected to realize a wide range of technologies, such as human interfaces, smart clothes, skin-motion monitoring, and robotic skin. Recently, carbon nanotubes (CNTs) have been assembled into stretchable conductors, and are potential base materials for various flexible sensors. Herein, we construct a flexible stretching sensor from urethane elastomer and conductive electrodes from single-walled CNTs. This sensor is extremely thin (thickness: $150~\mu $ m), and characterized by high elasticity (up to 100%), low stress (0.8 MPa at 100%), durability (1000 cycles at 50%), light weight (approx. 1.1 g/ $\mathrm{cm}^{3}$ ), and sensitivity (1 pF/ $\mathrm{mm}^{2}$ ). The strain sensor is tested on a cloth fabric, and is confirmed to measure the stretch area of flexible materials.