Durable, region-specific protein patterning in microfluidic channels.

We present a straightforward, accessible method to covalently pattern proteins in poly(dimethyl siloxane) (PDMS) microchannels. Our approach includes (i) region-specific photografting of a layer of poly(acrylamide) (PAAm) and (ii) bioconjugation of PAAm with a desired protein. The method produces symmetric protein patterns on all channel walls, which have high specificity and pattern fidelity, are compatible with a variety of geometries and exhibit excellent longevity under shear stresses of up to 1 dyn/cm. We demonstrate the generality of the method by creating multi-protein gradients within microfluidic microchannels and by in-situ patterning of islands of multiple proteins. Protein activity was observed by the digestion of BODIPY-casein using channels patterned with trypsin.