My friend is graduating soon as a veterinarian and we'd like to make fun of his shaky hands (which is why he's not ever going to do surgery in real life).

The idea is to build a thing where he has to collect tiny objects using a metal tweezer. Those tiny objects are surrounded by aluminum foil, which is connected to some voltage source and then to the hand which he's using to hold the tweezer.

The intent is that if he touches the aluminum with the tweezers, his hand is lightly shocked.

I am doing some tests with 9V batteries, which are new and my tester shows at 9.5 volts. While I can feel the mild tingling if I lick a single battery, I can't feel anything going across my finger if I bridge the gap, no matter whether I wire the batteries in parallel or in series.

Is it possible to achieve a mild shock across a finger with 9V batteries?

Is it safe? The current isn't going anywhere near his torso, and it's not a lot of current, but still...