One-step Non-uniform Photolithography System for Three-dimensional Conically Shaped Microwell Fabrication

Conical microwells are utilized in a wide range of biological applications such as cell spheroid formation, drug screening, cancer diagnostics, and three-dimensional oncology models. The shape of a microwell is an important parameter that defines its applicability. Currently, there exists no facile fabrication method for the creation of such conically shaped microwells. In this study, we develop a new platform based on non-uniform photopolymerization that effectively facilitates the synthesis of three-dimensional (3D) polymer-based conical microwells on a glass substrate in a simple 2D microfluidic channel. We also numerically investigate the parabolic curvature formation of microwells using non-uniform photolithography (NUPL) via incorporation of spatiotemporal free-radical diffusion into the modeling of photopolymerization to gain insights into its key mechanisms. We also perform numerical simulations to model the 3D-shape tuning ability of NUPL for the microwell synthesis through a variation of UV light intensity induced by the presence of opaque materials. The result of this study leads to characterize the morphological microwell shape change experimentally through a variation of UV light intensity and fluid opacity. Simply by manipulating the non-uniformity of the incident UV light, we are able to fabricate 3D V-shaped microwells with various bottom shape features. Notably, our method allows one to optimize and design polymeric microwells with shape features tuned to their application.