Scalable patterning using laser-induced shock waves

An advanced direct imprinting method with low cost, quick, and minimal environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni₅₀Ti₅₀ shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of aluminum, and copper grid. Laser pulses at different energy densities which generate pressure pulses up to a few GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the surface. Scanning electron microscope (SEM), atomic force microscope (AFM), and optical microscope images show that various patterns were obtained on the surface with high fidelity. Optical profile analysis indicates that the depth of the patterned sample initially increase with the laser energy and later levels off. Our simulations of laser irradiation process also confirm that high temperature and high pressure could be generated when laser energy of 2 J/cm² is used.