If you need a simple capacitive touch sensor to our project, Microchip's CAP1203 is a good choice. It is a multiple channel capacitive touch sensor controller with calibrated to compensate for system parasitic capacitance and automatically recalibrated to compensate for gradual environmental changes. The best thing about this chip is low power consumption at deep sleep mode. It can be used as a touch slider and worked under 6 mm thickness of plastic or wood or almost any materials.
PCB pad Design as below.
