One-step maskless grayscale lithography for the fabrication of 3-dimensional structures in SU-8

We propose a novel and simplified method to fabricate complex 3-dimensional structures in SU-8 photoresist using maskless grayscale lithography. The proposed method uses a Digital Micro-mirror Device (DMD®) to modulate the light intensity across a single SU-8 photoresist layer. Top and back-side exposure are implemented in the fabrication of original structures such as cantilevers, covered channels with embedded features and arrays of microneedles. The fabrication of similar structures in SU-8 with other techniques often requires complex physical masks or the patterning of several stacked layers. The effects of critical process parameters such as software mask design, exposure and developing conditions on the quality of 3-D structures are discussed. A number of applications using bridges, cantilevers and micromixers fabricated using this methodology are explored.