Static electricity depends on materials' contact history

Yes, the famous smooth chair in daycare. This blue plastic chair always had a heavy static buildup and would painfully shock you no matter how many times it was discharged. The chair's texture was rubbed smooth from years or decades of kids sitting in it. I think they threw it out after a while because it was cruel to use it as the timeout chair. https://imgur.com/rn54n2Q

> Among all the parameters they investigated, only one provided any hint at all: they spotted discrete changes in the materials' surface roughness at the nanoscopic scale.

> More concretely, they showed that contacts smoothed the tiniest bumps on a material's surface. How this causes contact electrification the team does not know, but as it is the only change they could detect, it is highly suggestive.

That suggests future experiments require some way to supply samples with where their surfaces (not just their charge) are in a known starting state. I'd say "just grind it down", but whatever you're grinding with also needs to have a standard state.

Perhaps something where a grinding/smoothing material is melted and then re-solidified between uses?

Did they just discover what every cat owner already knows?

After 200 contacts they detected persisting tribological electrical series ranking, but then found surface roughness changes too. So.. it's correlation heading to a theory of causation.