Fabrication of microchannel using planar photolithography

We have developed a new method for fabrication of microchannels and microcavities using only planar lithography processes. In this approach, microchannels are formed by spin-coating resist, exposure and development. Since only photoresist is used as the material and only standard lithography processes are employed in fabrication, this method is completely compatible with electronics that may have been fabricated on the same substrate. For single level microchannels, the resist is first exposed with the sidewall patterns of the channels. This is followed by another exposure with enhanced absorption to seal the channel. Enhanced absorption is achieved by mismatching the resist and the exposure wavelength. The latent channel structure is finally revealed by development. This approach can be further extended to fabricate complex multi-level microchannel system by repeating the basic approach. In this work, we fabricated single level channel up to 1.2mm long with 4μm by 2μm cross-section and demonstrated its utility by flowing water through it. We also fabricated multi-level microchannel system with unique 3D structure using the extended approach.