Design of a tomographic projection lithography system and material for roll-to-roll fabrication of 3D microstructures

Abstract

Large area arrays of three-dimensional microstructures are widely used in electronics, surface engineering, microfluidic chemical synthesis and diagnostics, and filtration. Current roll-to-roll (R2R) fabrication techniques have improved production speed of arrays of primarily two-dimensional structures, but they must resort to sequential multi-step lamination or deposition processes if more complex 3D structures are desired. We describe a single-step volumetric light-based approach that is enabled by tomographic light exposure, called R2R computed axial lithography (CAL). We describe the geometric freedom of the system and analyze the resolution of the dynamic projection optical system that supports lateral scanning and axial focus scanning. Additionally, we introduce a solid-phase photoresist that is compatible with tomographic light exposure of material coated on a web and capable of feature sizes as small as 20 μm. These developments illustrate how the R2R CAL process could streamline R2R fabrication of unprecedented 3D microstructures with reentrant features and internal voids.