Designer-Hyun Jin Yoon and Eun Hak Lee created a camera phone concept called "The Maple", covered in thin wooden film with touch sensitive buttons that light up through the housing when you touch the phone. The cell phone measures 4.5 x 10.4 x 9.8 cm and is a slider with functions like calling, texting, MP3 player and digital camera. The touch-sensitive sensors located in the back of the housing turn on the backlight, responding to your finger touch, bringing the wood to life. It would probably use the capacitive touch technology, which is a special panel coated with indium tin oxide or a similar material capable to conduct continuous electrical current across the sensor.
Source : Yanko