A study of the functional capabilities of shape memory alloy-based 4D printed analogous bending actuators

The 4D printing technique is employed to develop dynamic parts, such as actuators, smart material-based soft robotic devices, etc., which reorient their shape on exposure to external stimuli. In the present study, a novel in-house 4D printer is employed to build analogous bending actuators by integrating one or more Shape Memory Alloy (SMA) wires of 1 and 0.5 mm in diameter as hinges. The debonding strength is enhanced by incorporating larger (for four wires of o0.5 (50.43 N) to double wires of o1 (130.57 N)) and multiple SMA (for single wire of o1 (106.52 N) double wires of o1 (130.57 N)) wires and increasing its surface roughness at the matrix-wire interface. The functional capabilities and time response are evaluated with an experimental setup comprising a curvature block. The study divulges that using multiple SMA wires in the actuator enhances the actuation force, and the energy required per unit applied load to recover the actuator's shape post-unloading is higher at lower loads. The actuation time is reduced from 28 to 6s by increasing the magnitude of current and by incorporating thinner wires in the 4D printed structures. Numerical simulations are carried out to predict the bending behaviour, and a deviation of magnitude of less than 10% was achieved for the 4D printed analogous actuators. Finally, the built actuator can be employed to develop a self-assembly cube for rehabilitating small-medium-scaled wildlife, intending ethological investigations.