Micromachining of microfluidicsystems using a nanosecond laser : Process optimization and application

Microfluidics is a field of research that enables the manipulation of fluids in the submillimetre length scale. The technology allows the development of lab-on-a-chip devices, which are miniaturized systems for chemical and biological analysis. Currently, the conventional manufacturing methods for these systems require multiple time-consuming steps. Therefore, focus has shifted towards laser micromachining as an alternative method. Direct laser writing would circumvent many of the steps required for the conventional methods, drastically reducing the process time. In this Master thesis project, it was shown that microfluidic chips can be manufactured using a Nd:YVO4 (532 nm) nanosecond laser system. The process was optimized for silicon and borosilicate glass substrates. Acoustic focusing of polystyrene beads was demonstrated for a system etched in silicon. The optimized process used a power of 50%, a frequency of 10 kHz, a scan speed of 60 mm/s with triple lines as fill type and it had an etch rate of 4.3 μm/pass. Processed wafers were cleaned in buffered HF and bonded using anodic bonding as well as adhesive bonding. Processing of glass proved unpredictable, resulting in cracks and chippings. However, in- and outlets were successfully etched through thin glass wafers. It was found that crucial factors for the process were to control the focus, positioning of structures, structure orientation and the pulse separation for a uniform distribution of pulses. Based on the results, it is estimated that the manufacturing process could be done in two to three days using the laser micromachining process