Application of metal film protection to microfluidic chip fabrication using CO2 laser ablation

The CO2 laser ablation is a common technique for patterning the microchannels and holes used in microfluidic devices. However, the ablation process frequently results in an accumulation of resolidified material around the rims of the ablated features and a clogging of the base of the microchannel. In the article, these problems are resolved by means of a proposed metal-film-protected CO2 laser ablation technique. In the approach, the substrate is patterned with a thin metallic mask prior to the ablation process and the mask is then stripped away once the ablation process is complete. The feasibility of the proposed approach is demonstrated by fabricating two micromixers with Y-shaped and T-shaped microchannels, respectively. It shows that for a designed channel width of 100 mu m, the metallic mask reduces the ablated channel width from 268 to 103 mu m. Moreover, the bulge height around the rims of the channel is reduced from 8.3 to < 0.2 mu m. Finally, the metallic mask also prevents clogging in the intersection regions of the two devices. The experimental mixing results obtained using red and green pigment dyes confirm the practical feasibility of the proposed approach.