Characterization of an electrothermal gripper fabricated via extrusion-based additive manufacturing

Here, a MEMS-inspired, chevron-based electrothermal actuator fabricated using material extrusion-based manufacturing of shape memory polymer composite was computationally and experimentally investigated. The operational feasibility of the gripper design was determined by transient and steady-state finite element analysis. By varying the resistivity of the composite, the operational voltage range was determined; using a resistivity of 1.8 Omega-cm led to similar to 100 mu m tip displacement with an operational voltage as low as 3 V. Transient analysis showed that the grippers can be actuated quickly (3-5 s) with voltages as low as 5 V but recover slowly (60-100 s). The actuator was 3D printed and its actuation characterized using a laser Doppler vibrometer and a thermal camera. Experimentally, higher voltages were required for actuation; a tip displacement up to 77-117 mu m was achieved in 5 s with an operational voltage of 17.5-19.5 V. As predicted by the simulation, recovery took significantly longer time than actuation. The actuation and recovery mechanisms were further studied by correlating the observed displacement against the maximum temperature in the chevron. The results show a unique hysteresis in the latter relationship, which explains the difference between actuation and recovery times. While the actuator design implemented here was not application-specific, the results justify further research and development of application-specific electrothermal actuators made by extrusion-based manufacturing. (C) 2021 Elsevier B.V. All rights reserved.