In this paper, recent work on picosecond and nanosecond hybrid laser treatment of mechanically sawed single-crystal silicon wafer is presented. Surface morphology, surface roughness and phase development has been analyzed by 3D laser scanning confocal microscope (LSCM), X-ray diffraction (XRD), and scanning electron microscope (SEM). Results show that as-received surface defects including SiO2 layer and saw-mark defects have been significantly reduced, while average surface roughness has been decreased. No obvious damages such as micro-cracks and micropores have been observed at the laser-treated surface. Moreover, residual stress and electrical resistivity of laser-treated surface has been measured, respectively. The insights obtained in this work provide a facile method to improve surface quality of mechanically machined silicon wafer.
This paper presents magnetic-field-assisted femtosecond laser drilling of bone with deep drilling depth, good surface quality and high removal rate. In this study, the feasibility of producing deep cavity under magnetic field condition is investigated. When magnetic field is introduced, the depth of drilling hole is increased from 236μm to 483μm, and the removal rate is increased from 3.04×10-3 mm3/s to 5.46×10-3 mm3/s. Moreover, no thermal damage including carbonization is observed during laser drilling process.
Although magnesium and magnesium alloys are considered biocompatible and biodegradable, insufficient biocompatibility in body fluid environment is still the major drawback of magnesium alloys for their successful applications as biodegradable orthopaedic implants. In this work, magnesium alloy surface with both enhanced corrosion resistance and better cell adhesion property was directly fabricated by laser surface processing. Laser surface melting was used to improve corrosion resistance of Mg-6Gd-0.6Ca alloy. After laser surface melting, laser surface texturing was utilized on melted surface for better cell adhesion property. The corrosion resistance of laser-treated and as-received samples were evaluated using electrochemical technique. The effect of laser surface treatment on phase and microstructure evolution was evaluated using scanning electron microscopy, optical microscopy and X-ray diffraction. This work investigated the effect of laser treatment on cell distribution across the surface of magnesium alloy substrates. Osteoblast was cultured on the laser-treated surface and as-received surface. Cell morphology was observed with a scanning electron microscopy, and cell viability was evaluated by optical density measurement.
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