Laser Direct Writing of Thick Hybrid Polymers for Microfluidic Chips

This work presents patterning of thick (10–50 μm) hybrid polymer structures of ORMOCER by laser direct writing. ORMOCER combine polymer-like fabrication processes with glass-like surface chemistry that is beneficial for many bio-microfluidic applications. ORMOCER is liquid before exposure, so patterning is done by contact-free lithography, such as proximity exposure. With laser direct writing, we obtained higher resolution patterns, with smaller radius of curvature (~2–4 μm), compared to proximity exposure (~10–20 μm). Process parameters were studied to find the optimal dose for different exposure conditions and ORMOCER layer thicknesses. Two fluidic devices were successfully fabricated: a directional wetting device (fluidic diode) and an electrophoresis chip. The fluidic diode chip operation depends on the sharp corner geometry and water contact angle, and both have been successfully tailored to obtain diodicity. Electrophoresis chips were used to separate of two fluorescent dyes, rhodamine 123 and fluorescein. The electrophoresis chip also made use of ORMOCER to ORMOCER bonding.