Abstract
This paper reports the process of creating bumps on the surface of polystyrene (PS) induced by a CO2 laser at low powers. The paper also outlines the procedure for growing bumps induced by multiple laser scans on the aforementioned bumps. These bumps result from the net volume gain of the laser heat-affected zone on the PS rather than from a deposition process, and the expansion of the heat-affected zone on PS was verified by measuring the hardness change using nanoindentation. The bumps have a much smoother surface than microchannels fabricated with laser cutting; depending on the laser power, they have heights ranging from hundreds of nanometers to 42 mu m. The laser scanning speed and scan times along with this technique offer a fast and low-cost alternative for fabricating molds for multi-depth PDMS microfluidic devices.