Using Femtosecond Laser to Fabricate the Interior 3D Structures of Polymeric Microfluidic Biochips

We have successfully employed femtosecond laser to craft microstructures on polymeric substrate to imbed micro-mixiers. Since the laser pulse is ultra-short, the heat affected zone is not significant. Therefore the thermal melting damage is not as severe as that using continuous carbon dioxide laser. As a result, using femtosecond laser the fabrications of reproducible and defined micro-structures are able to accomplish. These structures can be used to generate micro-vortices using the mechanisms of induced electro-osmosis, one unique technique developed in our laboratory. The dimensional reproducibility of microstructures was observed with scanning electron microscopy. In addition, using attenuation total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to inspect the laser fabricated surface of polymeric substrate, we have acquired the spectrum of polymer moieties showing that photothermal effects are also more pronounced than photochemical effects in the fabrication processes to avoid surface reactions. An example of a micro- mixer with three dimensional microstructures about 800 mu m x 400 mu m x 65 mu m on the last slide for transparent glycerol and glycerol with red dyes mixing is presented.