Simple, Low-Hysteresis, Foldable, Fabric Pneumatic Artificial Muscle

Soft robots offer advantages over rigid robots in adaptability, robustness to uncertainty, and human safety. However, realizing soft actuators for these robots is still a challenge. We present a simple, highly conformable pneumatic artificial muscle made of a thin, single layer of woven, bias-cut fabric. The airtight fabric is adhered together with a flexible adhesive, negating the need for a bladder or sewing. Thus, it is foldable when depressurized and behaves like a McKibben muscle when pressurized, but without the friction of a bladder or braided sheath. Experiments show that the muscle exhibits repeatable, near-linear behavior with less than 1% hysteresis, over an order of magnitude less than that of McKibben muscles. Dynamic testing shows that the muscle responds quickly, even at lengths over 60 cm, contracting in 0.03 s, an order of magnitude quicker than series pouch motors. A fatigue test shows that its life exceeds 100,000 cycles. We also demonstrate that the muscle is well suited for steering tip-extending robots, and actuating folding, deployable structures. Our muscle offers improvements over various existing pneumatic artificial muscles, providing a simple new option for soft robotic actuation that has potential to advance the field.