Abstract
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.
Highlights
Thick polymer layers patterned by lithography have emerged as important materials in microfluidics
Laser direct writing (LDW) of thick photostructurable polymers is emerging as an interesting new technology for microfabrication [5] but there are still only few articles published on this topic
In this work we show how the hybrid polymer ORMOCOMP® is patterned by laser direct writing (LDW)
Summary
Thick polymer layers patterned by lithography have emerged as important materials in microfluidics. Benefits of ORMOCOMP®, in comparison to other lithographically patternable microfabrication polymers, are manifold: (i) adaptable elasticity modulus range (0.05 GPa to 2.35 GPa); (ii) low polymerization shrinkage of just 4.0%–5.8% by volume; (iii) solvent-free composition; (iv) thermal stability (cured ORMOCER® material tolerates temperatures up to 300 °C); (v) oxide-like surface chemistry when cured; (vi) self-adhesive bonding; and vii) ORMOCER® processing is simple and fast because it is solvent free—bake and developer times are just a few minutes compared with tens of minutes for photoresists of similar thickness. In this work we show how the hybrid polymer ORMOCOMP® is patterned by laser direct writing (LDW). In this work we explore the process conditions in detail Maskless methods, such as laser direct writing, are ideal for prototyping new device designs. We have explored LDW parameters, using different thicknesses of ORMOCOMP® and optimized the LDW parameters to obtain the microstructures down to micrometer range, with aspect ratios of 5:1
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