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

• Spatially defined hydrophobic coating was achieved on microwell-patterned substrate.
• Submicron-scale microwells were fabricated using UV curable polymer.
• PDMS contact onto a partially cured polymer and UV curing induced silicone transfer.
• A surface with dual wettabilities (hydrophilic/hydrophobic) was obtained.
• Targeted immobilization of functionalized beads into microwells was demonstrated.

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 30 min. 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 3 h 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.

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