A Numerical Model of Heating and Cooling Cycles to Study the Driven Response for Twisted and Coiled Polymer Actuator

Twisted and coiled polymer actuator (TCPA) is a type of artificial muscle that can be driven by heating due to its structure. A key issue with TCPA performance is the low driven frequency due to slow heat transfer in heating and cooling cycles, especially during cooling. We developed a numerical model of coating heating and nitrogen gas cooling that can effectively improve the driven forces and frequencies of the TCPA. Results indicate that natural cooling and electric fan cooling modes used in many experiments cannot restore the TCPA to its initial configuration when driven frequencies are high. Nitrogen gas cooling, at high driven frequencies, can fully restore the TCPA to its initial configuration, which is crucial for maintaining artificial muscle flexibility. In addition, as driven frequency increases, the corresponding driven force decreases. Systematic parametric studies were carried out to provide inspirations for optimizing TCPA design. The integrative computational study presented here provides a fundamental mechanistic understanding of the driven response in TCPA and sheds light on the rational design of TCPA through changing cooling modes.