An optical switch includes a substrate with a waveguide-coupling area and a fluid channel with an anti-wetting layer on a first surface. First and second fluids are on the anti-wetting layer in the fluid channel and at least one fluid is selectively movable relative to the waveguide-fluid coupling area. A fluidic driving mechanism has at least one electrode positioned to apply an electric field to at least one of the fluids in the fluid channel and is capable of moving at least one of the fluids in the fluid channel. The anti-wetting layer has an alkyl silane coating, which includes alkyl silane molecules covalently bonded to the first surface of the fluid channel.