Guidelines on the design, characterization, and operation of shape memory alloy knitted actuators

Textile actuators combine the intriguing mechanics of textile architectures with the multifunctional capabilities of active materials to provide large, distributed and three-dimensional deformations and forces. Shape memory alloy (SMA) knitted actuators, a type of textile actuator, are specifically alluring because of their high energy density and mechanical performance. The study of textile actuators in general, and SMA knitted actuators in specific, is currently confined to small parameter studies and application-driven research resulting in a scarcity of conclusive, universal guidelines and standards for the design, operation, and characterization of these compliant smart actuators. This paper identifies the predominant functional dependencies between the knitted actuator geometry, thermo-mechanical loading, and the knitted actuator performance to derive guidelines for the design, operation, and characterization of SMA knitted actuators. Through this first conclusive description of SMA knitted actuators, we significantly advance their research, design, and usability, while providing transferable insight into other active textile implementations and encouraging the standardization of language and procedures across this novel research field.