Fabrication and Characterization of I-cord Knitted SMA Actuators

Knitted SMA actuators provide greater actuation stroke than single-strand SMA wire actuators by leveraging its knitted structure. However, due to short-circuiting through interlacing knit loops, existing knitted SMA sheet actuators are unsuitable for joule-heating actuation when uniform contractile actuation is desired. We explore an axially symmetric tubular i-cord knitted actuator as a possible solution. The fabrication process of an i-cord knitted SMA actuator and its electrical, thermal, and mechanics models are presented. After modifying existing models for single-strand SMA wire and adjusting their parameters, the proposed electrical, thermal, and mechanics models were verified with experimental results.