Direct Laser Shockwave Imprinting of Shape Memory Alloys with Tunable Surface

Shape memory alloys (SMAs) are a unique class of smart materials with widespread applications in biomedical and aerospace technologies. In this study, we demonstrate an efficient and low-cost laser shockwave-assisted direct imprinting method to fabricate thermally controllable surface patterns on Ni₅₀Ti₅₀ (at.%). Patterned micro-indents were produced using a 1064 nm Nd:YAG laser operating at 10 Hz. The effects of laser energy, shape recovery behavior of NiTi, and shockwave dynamics were investigated experimentally and numerically. Focused laser pulses on the NiTi surface generated transient pressure pulses reaching several GPa. Optical microscopy revealed that the resulting surface patterns exhibited tunable geometries, with the imprint depth increasing as a function of laser power and irradiation time. Upon thermal activation, partial recovery of the patterned features was observed, with a maximum depth recovery ratio of ~30%. As the number of pulses—and consequently the well depth—increased, the recovery ratio decreased and plateaued near 15%. Finite-element simulations of pressure evolution in the SMA correlated well with experimental results, capturing the rapid rise, decay, and attenuation of stress waves within the material. Ongoing experiments employing picosecond laser-induced shockwave imprinting will also be discussed.