A FR2 PCB ("Pertinax") with copper on only one side. Milling the center area with a 1mm drill and drilling two holes for some 1mm silver-coated copper wire:
(the ruler is in centimeter)
I've used some layers adhesive tape to avoid conductive contact of the finger and the sensor.
The capacitance, measured with a HM8018 LCR meter (25kHz test frequency), is about 1.7pF. If the finger is 5mm above the capacitor, the capacitance changes to 1.6pF. When touching the tape of the sensor, it changes to 1.4pF.
