tldr: Shear forces set up a nano-scale front/back electric potential difference.

Arxiv: [1]

SciTechDaily summary: [2]

And a shout-out to DI, where I saw the first link [3]

Edit: Dupe [0]

[0] https://news.ycombinator.com/item?id=41603387

[1] https://arxiv.org/pdf/2408.16083

[2] https://scitechdaily.com/groundbreaking-study-finally-reveal...

[3] https://www.damninteresting.com/