| Summary: | Maskless lithography has a broad prospect in fabricating 3D microstructures by negative photoresist SU-8, which is popular in MEMS and microfluidics application. Thus, in this dissertation project, I study the optimal UV exposure condition for the DMD-based maskless lithography and build some 3D microstructures by SU-8 photoresist.
For SU-8 3050 under 10x Lens, the optimal results are obtained at 60%intensity with 300s exposure time. For SU-8 3010 under 10x Lens, the optimal results are obtained at 50% intensity with 200s exposure time or 60% intensity with 300s exposure time. For SU-8 3050 under 20x Lens, the optimal results are obtained at 70% intensity with 100s exposure time. For SU-8 3010 under 20x Lens, the optimal results are obtained at 40% intensity with 400s exposure time.
The 3D SU-8 microstructures can be fabricated by multi-exposure or shallow exposure methods. The former one is suitable for stacked patterns and the other one is suitable for bridge structures. A micromixer and several micro bridges are fabricated and evaluated by SEM.
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