I really wouldnt recommend it. The tip is a wire placed down the centre of the other piezo tube. Enough plastic tape is wrapped around the wire to make it a snug fit against the inside of the tube. Perhaps someone can fill me in on what else goes into these things. This sample is at ground potential while the tip is at 1 or 2 volts.
Thin wires lead to the sample and the tip from the pre-amp board mounted on the same base.
Since the wire is merely cut at a sharp angle to hopefully get a sharp tip, I cannot be sure exactly what type of atom is actually at the tip itself. No reason really, it just happened to be a bit of wire that was handy and the right diameter. Yes, my bed. I told you this thing was HOME made. Its all very rough.