Enhancing the actuation speed of Nitinol shape memory alloy wires via laser-induced surface modification

This study investigates laser surface modification to enhance the actuation kinetics of Nitinol Shape Memory Alloy (SMA) wires. Using an optimized 20 W laser power with 1 mm marking pitch, discrete Optical Discolored Region (ODR ∼15 µm) were introduced to modify the thermo-mechanical response. Experimental results demonstrated a 34% reduction in dynamic actuation time and a 57% increase in actuation velocity compared to the unmarked control at low voltage 1.78 V. Under isobaric loading (0.18–0.42 N), the modified actuators exhibited a distinct positive load-dependence, achieving a peak stroke of ∼26 mm at 0.42 N—significantly outperforming the pristine wire which suffered from stroke saturation. Thermal profiling confirmed that surface texturing improved heat rejection, lowering peak actuation temperatures by ∼15%. While cyclic testing revealed a beneficial ∼30% “training effect” in stroke amplitude, it also highlighted a stability trade-off with accumulated residual strain (∼4 mm) at high loads, indicating a need for mechanical pre-conditioning. Thermomechanical hysteresis analysis confirmed that the laser-induced microstructure mitigates blocking stress, maintaining superior energy density under heavy loads. These findings demonstrate that laser patterning is a viable technique for developing high-frequency, rapid-response SMA actuators.