Development of a disposable Silicone–Graphite composite strain sensor for soft robotics applications

Abstract

This work proposes a disposable and flexible strain sensor based on Silicone–graphite composite as an alternative method for strain sensing applications in soft robotic systems. Flexible piezoresistive materials have emerged as a promising class of sensors due to their exceptional ability to convert mechanical loads into electrical output responses. For this purpose, a sensing structure is fabricated using low-cost, disposable, and easy-to-fabricate materials, with graphite powder of particle size 16-$60\mu m$ and Silicone being chosen as the main fabrication materials. Therefore, an innovative material composed of Silicone and graphite is introduced, functioning as a flexible strain sensor. The sensor is formed in a bone-shaped clamped–clamped beam with a rectangular cross-sectional area (4 × 3 mm). A simple electronic read-out circuitry is also implemented into the system. The proposed flexible strain sensor structure is shown to be capable of measuring a force resolution of 0.22292 mN. The minimum detectable force of the implemented sensor is 0.86 N, with a sensitivity of 1.9975 mV/(mN mV). The resolution of the sensor in terms of the normalized voltage change corresponding to the generated strain ratio is denoted as 3.81$\times$10${}^{-5}$ (V/V), and the minimum detectable strain ratio is 2$\times$10${}^{-5}$, with a sensitivity of 2.6926 (V/V)/($\Delta$L/L). Finally, it is reported that the sensor exhibits a stretchability ratio of approximately 33$\text{\%}$.