Blocking the symmetry of motion and the second law

[Papatom]

Hi,

The article below states that they made a material that blocks the motion of molecules in only one way but passing the other way is possible. See the article.

https://physicsworld.com/a/blocking-the-symmetry-of-motion/

This seems to me in contrast with the second law. You can for example make the pressure higher in one compartiment without using energy. Than you use the difference in pressure to produce electricity or motion or whatever. If you would have a closed system the temperature would drop. If you do not have a closed system you can produce energy infinite.

Can somebody explain to me what my mistake is?

 

[sophiecentaur]

Is this more than a small scale ratchet mechanism?
The introductory passage "A mechanical metamaterial that responds strongly to motion" is a bit confusing. What sort of "response" is involved?

You can for example make the pressure higher in one compartiment without using energy.

How would you achieve this? Would you not need an initial pressure difference to produce motion? You may be reading more into this than the Nature article seems to imply. The Physics World journalist's interpretation of what he read may not be the best source for the 'facts'. The original work could produce useful practical applications without violating thermodynamics laws.

 

[Dale]

This seems to me in contrast with the second law.

The article said nothing about violating the 2nd law. You are just making that up. From what the article described the material is stiffer in one direction than in the opposite direction. That is strange and potentially useful, but no violation of the 2nd law.

You can for example make the pressure higher in one compartiment without using energy. Than you use the difference in pressure to produce electricity or motion or whatever. If you would have a closed system the temperature would drop. If you do not have a closed system you can produce energy infinite.

This is also not even remotely implied by the article. You are completely fabricating this.

We do not discuss perpetual motion machines here. Thread closed

 

[DrClaude]

I will simply add that Feynman has a very good discussion of ratchets and the 2nd law of thermodynamics:

http://www.feynmanlectures.caltech.edu/I_46.html