Any conductive material can be used as a capacitive sensor. Instead of using ready-made capacitive sensor shields and soldering the conductive material to it, one can use a pre-coded capacitive sensor library for arduino. This entry shows experiments and the producstion of final sensors.
I found an electronic component and didn't know what's it for (no serial or product code on it). But one thing I know: When you have no education in electronic engineering, the best way to learn is to try out and see what happens.