A method and apparatus are provided for performing light-directed reactions in spatially addressable channels within a plurality of channels. The multiwall via structure includes an outer via coupled to a pair of the conductive layers, an inner via within the outer via and coupled to the same pair of conductive layers, and a dielectric layer between the inner and outer vias. The implant has a wedge-shaped profile to restore disc height and the natural curvature of the spine. An enable signal capable of switching the current switch is provided.