Micro-channel fabrication on NiTi shape memory alloy substrate using Nd3+: YAG laser

Microchannel has been fabricated on NiTi shape memory alloy (SMA) sheet employing nanosecond Nd3+: YAG laser in open-air and underwater processing conditions. Microchannels were fabricated using three different laser wavelengths (1064, 532 and 355 nm) and scanning speeds (4, 10, 14 mu m/s). A comparison of the effect of processing condition (open-air and underwater) and scanning speed on the kerf dimension has been examined. The scanning electron micrographs revealed no debris formation and no recast layer formation in underwater conditions whereas the surface irregularities were predominant in the open-air environment. Further, the influence of machining on NiTi in open-air and underwater was studied using UV-Vis spectroscopy. The austenitic phase attributed to shape memory characteristics was evident in processed material in comparison to unmachined material using the X-ray diffraction technique. In addition, differential scanning calorimetry demonstrated the phase transformation temperatures. The samples processed in open-air and underwater environment showed a significant shift in phase transformation temperatures. These laser-based processing techniques are highly useful in preserving smart material characteristics and fabrication of microchannels used in controlled volume drug delivery, microfluidic and waste or body heat-based actuated devices.