Design of a tomographic projection lithography process for roll-to-roll fabrication of 3D microstructures

The rapid production of three-dimensional microstructures across areas of many square centimeters, such as in a roll-to-roll printing system, is needed for many applications such as microfluidic channels in diagnostic chips, filters with precisely controlled pore size, and surfaces with self-cleaning properties or structural color. Most current methods for transferring 3D microstructures to large substrates involve either multiple sequential deposition and imprinting steps with sacrificial materials to define voids, or lamination of a series of two-dimensionally patterned layers. These techniques have limited throughput and present significant layer-to-layer registration challenges. We introduce a design for an optical patterning system that has the potential to create 3D microstructures in a photopolymer film with a single patterning step on a roll-to-roll web. The technique builds on the process of Computed Axial Lithography that we have recently introduced. In the proposed technique, time-evolving, projected patterns of collimated light illuminate a photopolymer film on a web where it rotates around a backing cylinder. The rotational motion of the web allows each point in the film to be illuminated from many angles sequentially. During the rotation, therefore, a 3D light dose distribution can be synthesized tomographically, with the ability to define 3D polymerized structures which may include re-entrant and encapsulated features. Here, we describe computational modeling of the expected spatial resolution, geometrical fidelity, and patterning speed with this method for relevant photopolymer materials.