Aspects of the subject disclosure may include, for example, an apparatus having a material having a through-hole, a gate coupled to the material for controlling a charge concentration of the material, a sensor, and a controller coupled to the material, the gate and the sensor. The controller can perform operations including applying a first voltage potential to the material to induce a flow of current in the material, applying a second voltage potential to the gate to adjust the charge concentration of the material, and receiving sensing data from the sensor responsive to a change in electrical properties of the material caused by a target traversing the first through-hole of the material. The through-hole causes a plurality of structural portions of the target to be misaligned with a direction of the flow current in the material. Additional embodiments are disclosed.