Microfluidic networks (mu FNs) were used to pattern biomolecules with high resolution on a variety of substrates (gold, glass, or polystyrene). Elastomeric mu FNs localized chemical reactions between the biomolecules and the surface, requiring only microliters of reagent to cover square millimeter-sized areas. The networks were designed to ensure stability and filling of the mu FN and allowed a homogeneous distribution and robust attachment of material to the substrate along the conduits in the mu FN. Immunoglobulins patterned on substrates by means of mu FNs remained strictly confined to areas enclosed by the network with submicron resolution and were viable for subsequent use in assays. The approach is simple and general enough to suggest a practical way to incorporate biological material on technological substrates.