Facile Fabrication Method of Conical Microwells Using Non-Uniform Photolithography

Microwells have emerged as a popular trapping platform for numerous biological applications because of their ease of use. 3D shaped microwells, such as conical wells other than a simple 2D profile, have received great attention because of their excellent capacity for the formation of 3D cancer spheroids. However, creating such conical microwells require a complex fabrication process, laborious procedures, and specialized equipment. Herein, a facile and single-step fabrication technique is developed to make microwells with a tapered-bottom. In this approach, non-uniform polymerization is implemented during photolithography to create conical microwells of poly(ethylene glycol) diacrylate on a glass substrate in a PDMS (polydimethylsiloxane) microfluidic channel. The non-cylindrical shape forms through the UV exposure and further develops during the washing step by the removal of excess unpolymerized monomer from the PDMS microfluidic channel. In combination with the non-uniform photopolymerization, this washing process results in microwells with 3D conical forms, offering control over shape and homogeneity. Notably, the technique allows additional control over the microwells surface morphology, that is, wrinkled and smooth surfaces. Finally, the effect of ethanol flow rates on the pore size is investigated.