Laser-induced bubbles can be formed by focusing a conventional nanosecond (ns) laser in a liquid. We recently developed a microfabrication technique (microfabrication using laser-induced bubble (microFLIB)) and applied it to polydimethylsiloxane (PDMS), a thermoset polymer. The technique enabled the rapid fabrication of a high-quality microfluidic channel on a PDMS substrate and selective metallization of the channel via subsequent electroless plating. In addition, we found out that this technique enables true three-dimensional (3D) microfabrication of PDMS so that a hollow microfluidics can be embedded in the polymer substrate. Furthermore, a through hole having high aspect ratio of more than 200 can be fabricated by the single laser scanning. In the experiments, a ns laser beam was focused inside uncured liquid PDMS and was scanned to generate line of laser-induced bubbles. In the microFLIB processing, the shape of the created bubbles was retained in the uncured PDMS for a while; thus, the line of bubbles generated by the laser scanning successfully produced a microfluidic channel on and inside the PDMS substrate after subsequent thermal curing. However, mechanism of this process still remains unclear. Therefore, in this presentation, we will introduce how the microFLIB works in detail and investigate the behaviors of the bubble in the uncured PDMS and explore how the bubble connect to each other during the microFLIB using pump-probe imaging technique.
