Biocompatibility enhancement of crystalline silicon induced by nanosecond laser pulses for biomedical device fabrication

Abstract

This thesis study aims to introduce nanosecond laser processing for the enhancement of biocompatibility of pure silicon for biomedical technologies. These results have the potential to contribute to the design of manufacturing processes of innovative biomedical devices and improve the quality of life. This research investigates the trends of various laser parameters including three scanning parameters (line spacing, overlap number, and scanning speed), pulse frequency, and laser power. Biocompatible in vitro assessment was conducted through the use of Simulated Body Fluid (SBF) and cell culturing with NIH 3T3 fibroblasts. The samples with smaller line spacing and higher overlap numbers showed more generation of SiO[subscript 2] nanofibres, which were shown to be biocompatible under SBF assessment. Scanning speed samples also showed an increase in biocompatibility at lower scanning speeds. Biocompatibility increased with frequency due to the hybrid amorphous SiO[subscript 2] being more prominent on high frequency samples and providing a favourable site for fibroblast cell proliferation. Fibroblasts also showed preference to higher powers. However, the heat affected zone immediately outside the ablated areas showed a mismatch of crystal orientations causing residual stress. These stress zones were avoided by cells, which lead to promising results for the potential in cell programming and manipulation.