Thin Water Acts Like a Solid

Roland Piquepaille writes "What happens when you compress water in a nano-sized space? According to Georgia Tech physicists, water starts to behave like a solid. "The confined water film behaves like a solid in the vertical direction by forming layers parallel to the confining surface, while maintaining it's liquidity in the horizontal direction where it can flow out," said one of the researchers. "Water is a wonderful lubricant, but it flows too easily for many applications. At the one nanometer scale, water is a viscous fluid and could be a much better lubricant," added another one."

Comments

But what is the channel made of?

[cyfer2000]

If it is hydrophobic, what we see may actually be the effect of lost entropy due to rearrangement of water molecules, rather than compression.

Re:But what is the channel made of?

[snoop.daub]

This is a hydrophilic channel. In a hydrophobic channel, the vapor phase is more stable than the liquid, so you get "cavitation" or "dewetting", as you approach the walls of the channel closer and closer, at some point all the water gets pushed out of the channel and the walls get pushed together.

The phenomenon is well understood in the hydrophobic case, both experimentally and in simulations. This experiment is new, up till now they couldn't get down to such small separations, but they are overstating the case when they claim that this is a complete surprise... as another poster said, many many simulation studies have suggested a structuring of water near hydrophilic surfaces.

Another neat thing happens when you have one wall hydrophobic and one wall hydrophilic. This has been dubbed a "Janus interface" after the two-faced Roman god, and there's a lot of interest in them.

Ripley's Believe It or Not Ball

[infosystech]

How about just outside the Gatlinburg museum's entrance, visitors can see a 5-ton solid granite ball floating and spinning on 1/264 of an inch of pressurized water. Visitors may put their hands on the 4-foot diameter ball and spin it in another direction. Or the Merchant Family Memorial (Ripley's Believe It or Not Ball).

Re:the actual reference...

[kebes]

For anyone interested, the figures in the paper show clearly the structuring of water in layers near the surface. Moreover they directly measure that the viscosity jumps up considerably for distances less than 2 nm. The viscosity goes from the bulk water value (9E-4 Pa*s) when far from the surface, and increases to as high as 50 Pa*s (500 Poise or 50,000 cP) in the last 0.5 nm. To give you an rough idea of what this means, note that 50,000 cP is similar to the (bulk) viscosity of things like honey or ketchup (for a random table of values, see here or here).

Of course this higher-viscosity persists only over a very short-range, but understanding these "nano-mechanical" properties is crucial for the design and construction of future nano-scale devices.

Duh, Roland

[iamlucky13]

Density and viscosity are the primary factors when choosing a lubricant. Water happens to have a pretty low viscosity. The point of article is that the effective viscosity increases by several orders of magnitude in truely thin sheets and takes an ordered form like a solid in one direction but not the others, not that thicker films of water can be used as a lubricant. In fact, they found that as the gap gets down to a nanometer, it becomes a less effective lubricant.

I started typing this and thought to myself, "Something about the way that submission is written and how it misses the point of the article smells of Roland Piquepaille."

I wasn't at all surprised when I went back and checked the author to see his name and standard question-link-quote writing format.

Now I'm curious because the pressure they apply seems to be of interest here. I'm curious if 3 dimensional order appears under high isotropic pressures. If so, I'd expect this to be possible in larger volumes with sufficient pressure, and I wouldn't be at all surprised if the viscosity increased, too.