Low-Distortion Surface Functionalization of Polymeric Microstructures

Polymeric microstructures can be immersed in an organic solution containing a reactive linker to functionalize the surface for attachment of nanoparticles, fluorescent dyes, proteins, DNA, and other species. However, organic media can swell and distort polymeric microstructures. Swelling and distortion can be irreversible when the linkers are themselves low-molecular-weight organics like ethylenediamine, which can bind to unreacted monomer groups or other functionalities within the polymer matrix. This work introduces an alternative approach for surface functionalization based on aqueous processing using higher-molecular-weight amines, which causes less distortion, but is comparably effective. The processes are compared by aminating crosslinked SU-8 thin films and 3D woodpile microstructures, electrolessly depositing copper onto these primed surfaces, and measuring the amount of copper deposited and the degree of distortion caused by amination. The method provides a new route to low-distortion SU-8 microstructures and identifies a path for improving related processing with other polymeric materials and structure types