Abstract
Fabrication of microfluidic devices by soft lithography is by far the most popular approach due to simplicity and low cost. In this approach PDMS (polydimethylsiloxane) is cast on a photoresist master to generate replicas that are then sealed against glass slides using oxygen plasma. In this work, we demonstrated fabrication of soft photolithography masters using lamination of ADEX dry film as an alternative to the now classic SU-8 resist masters formed by spin coating. Advantages of using ADEX dry film include the easily-achievable uniform thickness without edge bead; simplicity of the process with significant time savings due to non-sticky nature of the film; and fewer health concerns due to less toxic developing solution and antimony-free composition. As we demonstrate, the process can be performed in a low-cost improvised fabrication room in ambient light, in place of a conventional yellow-light cleanroom environment. We believe this approach holds the promise of delivering state-of-the-art microfluidic techniques to the broad field of biomedical and pharmaceutical research.
Highlights
Explosive growth of microfluidics in the past two decades has led to development of a number of fabrication approaches
The approach involves casting of PDMS on a photoresist mold formed by photolithography and can be accomplished without extensive instrumentation
We demonstrate fabrication of soft lithography masters using an antimony-free ADEX dry film photoresist (DJ MicroLaminates, Inc., Sudbury, MA, USA)
Summary
Explosive growth of microfluidics in the past two decades has led to development of a number of fabrication approaches. The approach involves casting of PDMS (polydimethylsiloxane) on a photoresist mold formed by photolithography and can be accomplished without extensive instrumentation. The most common technology enabling soft lithography is to pattern molds using SU-8 photoresist [12,13,14,15]. One downside is that it is difficult to obtain good flatness of the resist, potentially leading to non-uniform channel structure. This non-uniformity arises from the edge bead—a buildup of resist at the wafer edge as resist flows outward form wafer center under the influence of centrifugal force during spin coating. The disadvantage, is that in a poorly controlled process there can be considerable splashing and misting of the solvent leading to resist coating defects
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