Compact flexible actuator based on a shape memory alloy for shaping surgical instruments.

Conventional flexible actuators for minimally invasive interventions come with complex and bulky actuation infrastructure. We present a proof-of-concept study of a compact flexible actuator with variable shape change featuring shape memory alloy wire loops in active-antagonist configurations for a bending and S-shape. The actuator was fabricated using heat-treated wire loops. The evaluation using optical marker tracking revealed a mean maximum absolute displacement at the distal tip of 19 mm and a force of 90 mN reached in under 15 s. For control, a closed-loop regime was evaluated with steady-state errors below 2 degrees.