Actuator Materials for Environmentally Powered Engines

Abstract

The first solid‐state engine that converted heat into continuous mechanical motion using a thermally responsive actuating material was introduced almost a century ago. These engines used vulcanized rubber where the cyclically heating and cooling of the rubber generate continuous mechanical power in pendulum or wheel type engines. The development of solid‐state heat engines has seen several waves of activity with interest stimulated by the introduction of new actuating materials capable of responding to different environmental stimuli. Opportunities for improved engine outputs are afforded by recently developed artificial muscle materials. A theoretical connection between engine output and the characteristics of the actuator material is developed to compare the performances of vulcanized rubber, shape memory alloys (SMAs), and twisted and coiled polymer (TCP) fiber artificial muscles. It is shown that with an engine designed to suit the actuation performance of TCPs engines powered by the tensile actuation of such materials would exceed the output of SMA heat engines. The properties needed in actuator materials to further enhance engine output are identified and polymer structures that may produce such properties are described.

Machine Learning‐Enabled Precision Position Control and Thermal Regulation in Advanced Thermal Actuators

“…[1,2] They are easy to integrate into big systems, scalable (from nano to macro), can operate at low voltages, and can generate relatively large strains (up to 200%). [3,4] In particular, nylon artificial muscles are inexpensive (5 $ kg −1 ) and can lift loads over 100 times heavier than that of human muscle with the DOI: 10.1002/admt.202301769 same length and weight. [5,6] Despite these advantages, thermal artificial muscles also face challenges such as difficulty in controlling their position and temperature.…”

Continuous textile manufacturing method for twisted coiled polymer artificial muscles

“…These applications include active filters, thermaladjustable clothing or shading textiles, prostheses, power generation under diurnal temperature fluctuations, or active soft structures made of fiber-rubber composites. 29,30 While prosthetics and orthotics have been the main focus of TCPAs in recent years, there has been increasing interest in the field of energy harvesting in general, 31 and specifically in low-grade waste heat 32 in the past two years. In particular, for industrial use in low-grade waste heat recovery systems based on TCPAs, large woven belts would be ideal, but they require textile-processable, continuous highly twisted fibers, which were explored in this study.…”