Figure bellow shows how the 4088 or 4018 can be used as a touch switch. Two metal plates separated by 1 mm form the sensor. When both are touched at the same time, the two plates act as a switch and turn to a low-resistance state. See data for the 4088 for the currents to be controlled by this circuit. The circuit can operate with digital or analog signals. If working with analog signals, is important to avoid noise in the control input.
Touch Switch - 4066
