Modeling and Numerical Studies of Three-Dimensional Conically Shaped Microwells Using Non-Uniform Photolithography

Conical microwells have found a wide range of applications such as in cancer diagnostics, cell spheroid formation, and three-dimensional oncology models. Numerous microengineered fabrication techniques have been developed for the formation of such conically shaped microwells. Among many, non-uniform photolithography (NUPL) in a PDMS microfluidic channel with a glass substrate, can be used to create polymeric microwells with tapered-bottom and parabolic curvatures. Here, the parabolic well formation of microwells is numerically investigated using NUPL to better understand its key mechanisms. Temporal and spatial free-radical diffusion are incorporated into the modeling of photopolymerization. In addition, the 3D-shape tuning ability of NUPL is modeled for the synthesis of microwells through a variation of UV light intensity induced by the presence of opaque materials. The model and simulation results predict the time-evolution of microwell formation with parabolic well features. The effects of the conical shape-tuning parameters are numerically determined, i.e., the aspect ratio of the well diameter to channel height and the non-uniformity of UV light intensity on the microwell depth and parabolic curvature. Numerical work provides meaningful insights into NUPL to optimize and design polymeric microwells with shape features tuned to their application.