A versatile method to pattern surfaces within microfluidic devices

Microfluidic devices with surface-bound biomolecular patterns enable localised detection arrays, enzymatic catalysis, and gene expression. Photolithography is a contactless patterning method with high spatial control. However, while patterning open surfaces by photolithography is well-established, patterning enclosed microfluidic channels remains technically challenging. Such capability would enable in situ surface modification and precise pattern alignment to channel geometries. Here, we present a photolithographic method using commercially available reagents to pattern sealed microfluidic devices. We first coat surfaces with (3-Aminopropyl)triethoxysilane (APTES) to bond microfluidic chips and provide surface amine groups onto which photocleavable polyethylene glycol (PC PEG) compounds are bound. UV exposure using standard photolithography equipment selectively deprotects the amine groups, which can subsequently bind amine-reactive cargos. We demonstrate this methods versatility by patterning both glass and poly(dimethylsiloxane) (PDMS) surfaces with diverse cargoes: DNA, proteins and gold nanoparticles. We also compare covalent versus noncovalent DNA patterning. Covalently bound DNA patterns were denser and could be used for sequence-specific target DNA capture. However, noncovalently bound DNA yielded higher cell-free gene expression from surface-bound GFP templates.