A sensor is disclosed. In one embodiment, the sensor includes an insulating substrate comprising a first zone, a second zone, and an intermediate zone, where the intermediate zone comprises a portion of the second zone that overlaps the first zone. The sensor further comprises a first electrode in the first zone that comprises a first plurality of fingers of a conductive material, a second electrode in the second zone that comprises a second plurality of fingers of the conductive material that are interdigitated with the first plurality of fingers, a plurality of three-dimensional isolation structures, and a plurality of shadow zones, wherein each shadow zone is adjacent to at least one isolation structure and is substantially free of conductive material. The plurality of isolation structures may comprises hills and/or channels.