Spatially defined hydrophobic coating of a microwell-patterned hydrophilic polymer substrate for targeted adhesion with high-resolution soft lithography

Abstract

In this study, a simple and facile scheme for selectively hydrophobizing microwell-patterned hydrophilic polymer substrate is demonstrated, and applied for a targeted adhesion. Microwell-patterned polymer substrate was replicated from a silicon mold using a photocurable prepolymer under ultraviolet (UV) light for 30min. While the surface of the replica was partially cured, it was contact printed with a flat, hydrophobic poly(dimethylsiloxane) (PDMS) elastomer, and the assembly was further cured under UV light for approximately 3h and detached. In this manner, the PDMS molecules were transferred selectively onto the protruding regions of the partially cured microwell-patterned substrate, while the inner walls of the microwells remained hydrophilic. The surface hydrophobization was characterized by contact angle measurement and X-ray photoelectron spectroscopy (XPS). In addition, time-dependent contact angle variations were investigated to verify the robustness and durability of the coating of the PDMS functional group. As a proof-of-concept experiment, functionalized polymer beads were targeted and successfully guided selectively into arrays of microwells without being adsorbed onto the protruding regions of the microwell-patterned substrate, which could further be applied for the targeted immobilization of biomolecules with high selectivity in a relatively simple and facile manner.