Coating process for microfluidic sample arrays

A differentially coated device for conducting a plurality of nano-volume specified reactions, the device comprising a platen having at least one exterior surface modified to a specified physicochemical property, a plurality of nano-volume channels, each nano-volume channel having at least one interior surface in communication with the at least one exterior surface that is selectively coated with an optionally dissolvable coating agent physisorbed to at least one interior surface, wherein the optionally dissolvable coating agent comprises a coating agent and a first component for the plurality of specified reactions. Methods for preparing and using such devices are also provided, as well as a method of registering a location of a dispenser array in relation to a microfluidic array. A first one of the dispenser array and the microfluidic array is movable in relation to the frame, and the other of the first one of the dispenser array and the microfluidic array is fixed relative to the frame. Quantities related to a vector displacement from the alignment position to a fixed position on the one of the dispenser array and the microfluidic array is determined. The quantities thus determined are used to guide positioning of the dispenser array relative to the microfluidic array.