Nuclear

Some Erwin guy told me that the first step is to find a cat.

Jokes aside, the strategy seems elegant, even given the physical restrictions mentioned in the intro.

First, almost all charge changes are measured to be in the positive direction—i.e., the spheres nearly always lose more electrons than protons for both the α and β decays in the decay chain

This is bugging me a bit - why would α decay increase the charge? Since you're expelling a positively charged particle, I'd expect a decrease; and if the α particles are trapped on the silica, or steal electrons from it, you'd expect no change in charge. Perhaps the rest of the article mentions the reason (I'm still digging through it).