Reminder: Bacterial spore PM wheel

[broli]

Remember 5 years ago scientists used bacterial spores to essentially create a PM wheel.

https://www.youtube.com/watch?v=Vj2kuZm-aCA

The spores don't degrade, they are like a sponge, they expand when humid and contract when dry, you only need a difference between humidity to make it work. But what is most surprising is the reaction force when the spores get wet, which is near instant and their calculated work density being ∼17 J/kg. So power density can be huge seeing how fast this force can be applied. The only energy source applied is a small fan to make the evaporation happen quicker, but it's not part of the principle only to get fresh dry air around the spores.

The real energy source is the sun but there is no temperature gradient needed, it's sort of a maxwell demon. Evaporation happens because some molecules are faster than others, even if the temperature is overall the same, and escape.

The complete paper can be found here: https://www.nature.com/articles/ncomms8346

[agor95]

Well this gets you thinking how a common, in plain view, event can be used in another way.

Electrostatic capillary attraction on the input side and Electromagnetic radiation on the output.

P.S. I trust they are not using active bacteria. I think they need to synthesize the active compounds that cause this effect.

Cheers

[broli]

They are not. Bacterial spores are a dormant form of a bacteria that forms when conditions become too harsh (no nutrients, not ideal temp...) for sustained growth. There are some reports that bacterial endospores can last up to 10,000 years.

Btw you don't need capillary action or gravity. The spores can dip into water and pull the weight up at the bottom and dry off and push the weight out on the way up. The fast they dry the better obviously but this is a matter of scaling it up. Evaporation happens at a brought temperature range, so as long as you have water to evaporate the wheel keeps spinning.

[agor95]

You can say there is more to bacteria and water. So many things that can be used. Just need the eyes too see.

Cheers