Capacitive touch sensors are entirely in the domain of DIY, requiring little more than a carefully-chosen conductive surface ...

The sensor forms an image and OpenCV detects the actual touch configuration. It appears you can use the raw data from the Arduino, too, but it might be a little harder.

You can’t have a touch sensitive switch without a way to detect the presence of a finger! A touch sensor, especially a capacitive touch sensor, has some surprisingly sophisticated electronics to ...