Posted on 04/30/2006 12:13:33 PM PDT by blam
Scientists make water run uphill
By Roland Pease
BBC science correspondent
Watch the drop move Physicists have made water run uphill quite literally under its own steam.
The droplets propel themselves over metal sheets scored with a carefully designed array of grooves.
The US scientists did the experiment to demonstrate how the random motion of water molecules in hot steam could be channelled into a directed force.
But the team, writing in Physical Review Letters, believes the effect may be useful in driving coolants through overheating computer microchips.
The physics at work here has been witnessed by all of us in the kitchen.
Leave an empty pan on the stove for too long, and water, when you drip it over the scorching pan bottom, will hover over the surface on a bed of steam.
The effect was described in the 18th Century by a German scientist Johann Gottlob Leidenfrost.
What happens is that the heat is so intense, it boils the underside of the water droplet without any physical contact with the pan.
"We were interested in whether it would be possible to use this phenomenon to move liquids around," said Dr Heiner Linke, the intellectual power behind the self-propelled droplets.
An uphill struggle
The trick seems simple. Instead of using a smooth surface, the team scored it with a series of skewed triangular grooves. This gives it a kind of saw-tooth profile.
Now the water droplets appear to push themselves off the long-slope side of the grooves and rocket across the heated surface - instead of just dancing on the spot as they do in the kitchen pan.
The mechanism is a little more complicated and took a while to work out, Dr Linke told the BBC. "The vapour," he explained, "mostly flows in one direction, and the droplet sits on the flowing vapour, a bit like a boat carried along in a flowing river."
Droplets can also climb over steps, and up inclines of up to 12 degrees. Filmed with high-speed cameras, the droplets appear to take on a life of their own, sliding along like sloppy amoebae.
Although the original intention was to devise an arresting demonstration of how random energy can be rectified into directed motion - the focus of Dr Linke's main work is with molecular motors - the researchers now think there may be a use for the effect in cooling computer microchips.
The electrical currents now passing through microprocessors are so large the heat they generate can limit computing performance.
Many chips have cooling circuits nowadays, but these require pumps to drive the coolant, which in turn generate even more heat.
Suitably micro-patterned channels, argues Dr Linke, would make the coolant flow automatically.
"It would be very neat if we could use the heat from the chip to be the pump, because you would not need any additional power, but also because the pumping only happens when the thing is warm; it would also be a thermostat at the same time. So it would all be in one package."
An AESOP's fable come to life!!!
The water will get sleepy and move back downhill. It happens all the time. Mark my word.
Next up...a Liberal college professor in Florida changes his mind.....says Jesus walked on the water using this process instead of walking on ice(as he originally bloviated)....heat source was spontaneous combustion of Jesus feet boiling droplets of Galilean lake water!(sarcasm on)
You know Peter walked on water also...using faith.
Preprint (no subscription needed) available at http://arxiv.org/abs/physics/0512246; movies and short explanation available at the author's website.
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Ahhh! Witch!
...Actually, that is pretty interesting. Could be interesting to see what other applications it could be used for.
I know a few Taoists who are going to be very unhappy about this. Sun Tzu may have to revise all those statements about water flowing downhill.
Yeah...I wasn't trying to knock the Bible story...I was knocking that Florida professor I had read about!
Gee, I thought you could get water to run anywhere by showing it a pic with Helen Thomas, wearing either a bathing suit, or a shower cap....
Australian researchers have experimentally shown that microscopic systems (a nano-machine) may spontaneously become more orderly for short periods of time--a development that would be tantamount to violating the second law of thermodynamics, if it happened in a larger system. Don't worry, nature still rigorously enforces the venerable second law in macroscopic systems, but engineers will want to keep limits to the second law in mind when designing nanoscale machines. The new experiment also potentially has important ramifications for an understanding of the mechanics of life on the scale of microbes and cells.There's another article from a couple years ago that I can't find right now, where scientists were able to structure the physical environment surrounding a molecule or some kind of nanoparticle such that the random Brownian motion was channeled into a specific direction, like a ratchet. The idea there was, again, that the 2nd Law of Thermodynamics doesn't apply as forcefully to a very small object as it does to something on a macro-scale, and so nanoengineers can have a very different set of constraints to work with than engineers who build things on "our" scale.There are numerous ways to summarize the second law of thermodynamics. One of the simplest is to note that it's impossible simply to extract the heat energy from some reservoir and use it to do work. Otherwise, machines could run on the energy in a glass of water, for example, by extracting heat and leaving behind a lump of ice. If this were possible, refrigerators and freezers could create electrical power rather that consuming it. The second law typically concerns collections of many trillions of particles--such as the molecules in an iron rod, or a cup of tea, or a helium balloon--and it works well because it is essentially a statistical statement about the collective behavior of countless particles we could never hope to track individually. In systems of only a few particles, the statistics are grainier, and circumstances may arise that would be highly improbable in large systems. Therefore, the second law of thermodynamics is not generally applied to small collections of particles.
Ping.
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That looks like one gas of a ride.
But you'll also want to take the gravity ride on tube down the Guadalope(sp?) River. Texas Pride in hand.
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