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Water compresses under a high gradient electric field

phys.org

11–20 of 49 posts

Re: Water compresses under a high gradient electric field

#11
”Wilson found that a high electric field applied to a tiny hole in a graphene membrane would compress the water molecules travelling through the pore by 3 percent”

So, it changes the distances between the atoms of a water molecule? If so, would that mean this can affect chemical reactions involving dipoles, too?

Re: Water compresses under a high gradient electric field

#13
post #10
post #4

That is a really neat effect. Basically if you can put a water molecule inside a flat field it lines itself up with that field and can be compressed. I would bet this has an impact on Graphene based desalination efforts as well.

That type of filtering was also something that I had in mind. It would additionally be interesting if the water would react to EM fields and confined spaces in a way that allowed for a 'micro' pump. Such a system might be able to operate in zero-g and thus be useful on extended space missions.

That is a really good observation. Microgravity environments have an issue with the lack of sediment settling, and while the current centrifuge system are effective, it would be really interesting if you could separate the precipitates without spinning everything.

Re: Water compresses under a high gradient electric field

#14
post #9
post #5

Does this also mean compressing/decompressing water can generate an electric field?

Nah, probably not.from how i read it, is not that the field is strong, but that it's so incredibly localised. The molecules arrange along the field lines (H being more positive and O more negative). Since the field lines are so close in this case, and the field's gradient (more or less: inverse of width between field lines) is so high, the O parts snuggle together a bit more, as do the H parts. Anyway, that's how i r…

Well, maybe compressing water does not force molecules to align this way, bu enough pressure will cause water to align in a crystal lattice (not normal ice but something exotic like ice III, ice V, or ice VI).

Re: Water compresses under a high gradient electric field

#15
post #5

Does this also mean compressing/decompressing water can generate an electric field?

Probably, but it would take a lot of mechanical force. From the article: > The compression is only 3 percent, but that pressurizes the water—it's equivalent to 100 atmospheres Although, that's not uncommon for ice giants, so it might be causing part of Ouranos (aka Uranus) magnetic field. > The troposphere is thought to have a highly complex cloud structure; water clouds are hypothesised to lie in the pressure range…

Implication: Depending on the energy input, couldn’t you create an engine from this? Sounds like a perpetual motion machine.

Re: Water compresses under a high gradient electric field

#16

Earlier quoted context omitted.

Probably, but it would take a lot of mechanical force. From the article: > The compression is only 3 percent, but that pressurizes the water—it's equivalent to 100 atmospheres Although, that's not uncommon for ice giants, so it might be causing part of Ouranos (aka Uranus) magnetic field. > The troposphere is thought to have a highly complex cloud structure; water clouds are hypothesised to lie in the pressure range…

Implication: Depending on the energy input, couldn’t you create an engine from this? Sounds like a perpetual motion machine.

This effect does convert energy from mechanical to electrical, and so could be used in a type of engine. But AFAIK there would still be inefficiencies causing this conversion to be less than 100%, and so sadly not a perpetual motion machine.

Re: Water compresses under a high gradient electric field

#17
> "Physics Professor Aleksei Aksimentiev and his post doctoral researcher James Wilson found that a high electric field applied to a tiny hole in a graphene membrane would compress the water molecules travelling through the pore by 3 percent."

Ahh, "3 percent" means that from a fluid dynamics point of view, the incompressibility assumption is still a good assumption valid for most macroscopic applications. :) Still very impressive to achieve that under ambient pressure with an electric field gradient.

Re: Water compresses under a high gradient electric field

#18
post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

> I probably would have written it off as floating point shenanigans.

Pretty sure anyone in actual scientific computing stays far, far away from floating point numbers and sticks to arbitrary precision ones instead.

Re: Water compresses under a high gradient electric field

#19
post #18
post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

> I probably would have written it off as floating point shenanigans. Pretty sure anyone in actual scientific computing stays far, far away from floating point numbers and sticks to arbitrary precision ones instead.

Double precision floating point numbers are the most common in scientific computing. Sometimes software will mix in single precision for more speed. The molecular dynamics package GROMACS can use mixed single/double precision, for example:

http://manual.gromacs.org/documentation/2016/install-guide/i...

Re: Water compresses under a high gradient electric field

#20
post #18
post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

> I probably would have written it off as floating point shenanigans. Pretty sure anyone in actual scientific computing stays far, far away from floating point numbers and sticks to arbitrary precision ones instead.

I'm quite curious what niche of scientific computing you've dealt with that gave you that impression.
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