Capacitive touch sensing demo
Capacitive touch sensing allows to provide digital inputs with a simple touching of electrodes. In Arduino, the capacitiveSensor library can be used to convert two or more of its I/O pins into a capacitive sensor. This technique requires external resistors and metal foils to work properly. This Instructable describes a physical setup for making five capacitive touch sensors with the Arduino I/O pins.
Capacitive touch sensing with Arduino