Toward a Novel Thermal-Based Variable Impedance Module Through Adjusting Viscoelastic Properties of a Thermoresponsive Polymer

In this article, we propose a one-of-a-kind thermal-based variable impedance module to be used towards developing a variable impedance actuator. Unlike other variable impedance actuators, where the impedance adjustment modules employ a mechanism to regulate their impedance, this novel module does it through controlling temperature of a thermoplastic polymer Polycaprolactone. The viscoelastic properties of polycaprolactone are temperature-dependent, increasing the rigidity when it is cooling down and softening when it is heating up. To change the temperature, thermo-electric Peltiers are embedded into the design. Preliminary experiments have shown that this module is able to adjust its impedance through changing the temperature. The simplicity and lightness of the proposed off-line impedance adjustment approach make it a suitable choice when the actuator's size, weight, and compactness are the main concerns. This is because the proposed design is highly scalable, and by scaling down the size of the module, its performance regarding the speed of impedance adjustment would increase.