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Supercoiled polymer-actuated pinch valve

Supercoiled polymer (SCP) actuators have shown promising applicability as artificial muscles due to their low-cost, high strains (10%+), work density that is more than 100 x that of muscle, and non-hysteretic behavior. Here, we present a lightweight, low-cost, SCP-actuated valve that operates by pinching rubber tubing closed. The valve comprises a 3D printable frame and incorporates a pulley system, which functions to reduce the total linear dimensions of the device. The actuator mechanism is compatible with different tubing diameters and materials and, by nature of its design, is isolated from direct contact with the working fluid. Using 1/4”/6.3 mm inside diameter latex tubing, a flow rate of up to 88 L/h and a holding pressure of over 29.4 kPa are demonstrated. The valve is normally open and takes 10 seconds to close by running a current through the coiled, silver-coated nylon actuator. An empirical model of the system is developed and open-loop control incorporated, which effectively reduced valve activation time by 30%. Further developments are suggested to achieve a faster response and pumping action.