The University of California of Oakland has received US Patent No. 8,162,555, "Printing pins having selective wettability and method of making same." Printing pins are described that have an exterior surface and an interior surface that defines a lumen or capillary tract. The pins are treated to render the exterior and interior surfaces hydrophilic. The lumen or capillary tract is filled with a blocking material. The exterior surface of the pin is coated with a hydrophobic material. The blocking material is then removed.