Proximity of a body, which may be a user's finger, to an electrode pair is sensed by a charge transfer capacitive measurement approach. The electrode pair thus acts as a key that can be arrayed with other electrode pairs to form a keypad, keyboard, linear slider control, or liquid level sensor. In one...http://www.google.com.hk/patents/US6452514?utm_source=gb-gplus-share專利 US6452514 - Capacitive sensor and array
