Highly Sensitive Soft Foam Sensors to Empower Robotic Systems

Soft robots require seamless integration with sensors and actuators that are simple to manufacture at scale with low cost and minimum footprint. The sensor materials must be highly reliable, sensitive, and stable, and their mechanical features should match the sensing requirements of soft robots such as minimal response time and nonlinearity of hysteresis and relaxation. A resistive-type sensor based on the synthesis of poly(glycerol secabate) (PGS) with a foam-like structure and outstanding mechanical, electrical, and electromechanical properties is developed. These foam sensors present high sensitivity (gauge factor ≈ −9), very fast response (≤3 ms), negligible hysteresis, reliability, long lifetime (>1 200 000 cycles), and a pressure differential sensitivity of 34 Pa. They can accurately detect low and high frequency vibrations (up to 300 Hz) and small forces (200 mN) that cover the very low detection range of metallic strain gauges and the very large detection range of elastomeric strain sensors. These characteristics closely match those of the human fingertip, and hence pave the way toward tactile and compliant sensing elements embedded in prosthetic hands. Prospective applications for unexplored resistive-type sensors to meet the sensory requirements of soft robotic systems are demonstrated.