A prober head to interface an E-testing apparatus to a device under test, which may be an unpackaged die, for example. In some embodiments, the prober head includes an array of conductive pins, each of the pins extending outwardly from a first pin end anchored to a substrate. At least a partial length of each of the pins is coated with a hydrophobic monolayer. The conductive pins may be composite metal wires including a core metal encased by one or more peripheral metal. At a tip of the pins, opposite the first pin end anchored to the substrate, the peripheral metals are recessed from the core metal. In further embodiments, the hydrophobic monolayer is disposed on an outer surface of the peripheral metals, but is substantially absent from a surface of the core metal exposed at the tip.