Serious Magic Made From Brownian Motion

robertmcgrath

Nov 6

I don't understand how this is even possible. But apparently it is.

Everybody knows about Brownian motion. I learned about it is first grade. It's easy to understand (unless you think too deeply about it). But one thing seemed obvious—it's not something you can harness to do work. It's random and uncontrollable.

Ooops. What I "knew" was wrong about the last part.

This fall researchers in Shanghai report on experiments that demonstrate a "Molecular Thermal Motion Harvester" (it needs a flashier name, right?) [2]. Who knew?

The basic idea is that tiny piezoelectric whiskers, a few micrometers long, suspended in a fluid are bumped by the thermally moving molecules, generating tiny amounts of electricity. Enough molecules, whiskers, and collisions, and the device generates measurable amounts of electricity.

Combining the thermal energy of molecules—a.k.a. Brownian motion—with piezoelectric materials, Chinese researchers see possibility for a new source of nanoscale electricity.
Image Credit: Yucheng Luan and Wei Li (From [1])

For free! From nothing but heat and the piezoelectric twisting of molecules.

It works at room temperature, indeed, at any temperature above absolute zero. As expected, the warmer, the more electricity output.

The effect requires a nice clean fluid that is sitting really still. But otherwise, the overall device is easy and cheap to make, and there are lot's of materials to try out. So who knows what can be made to work?

The demonstration generated a tiny amount of electricity (2.28 millivolts and current of 2.47 nanoamperes at room temperature). But, hey, the dog actually danced, which is the big news here!

This is so cool!

Payal Dhar, Einstein Made It Famous; Tech Makes It Current, in IEEE Spectrum - Energy, October 27, 2023. https://spectrum.ieee.org/brownian-motion-einstein-nanoscale
Yucheng Luan, Fengwei Huo, Mengshi Lu, Wei Li, and Tonghao Wu, Molecular thermal motion harvester for electricity conversion. APL Materials, 11 (10):101118, 2023. https://doi.org/10.1063/5.0169055