Smart pneumatic artificial muscle actuator with embedded microfluidic sensing

We describe the design, fabrication, and characterization of a novel pneumatic artificial muscle actuator with embedded contraction sensing. The muscle is composed of three main components: elastomer air chamber, embedded Kevlar threads, and a helical microchannel filled with a liquid conductor. When the air chamber is inflated with compressed air, the constrained length of the Kevlar threads causes the muscle to contract in the axial direction. During this contraction, the microchannel can detect the shape change of the muscle by sensing, the expansion of the air chamber. This sensing capability increases the controllability of pneumatic muscles. A novel manufacturing method is proposed to embed Kevlar threads and a helical microchannel in an elastomer tube. Then, a liquid metal is injected into the microchannel to make a soft sensor that can detect the geometrical change of the muscle. The muscle prototype was characterized to demonstrate its actuation and sensing capability.