Scientists create metal that pumps liquid uphill
June 2, 2009
Chunlei Guo uses the femtosecond laser (behind him) to create nanostructures in metal that can move liquid uphill. Credit: Richard Baker, University of Rochester
(PhysOrg.com) -- In nature, trees pull vast amounts of water from their roots up to their leaves hundreds of feet above the ground through capillary action, but now scientists at the University of Rochester have created a simple slab of metal that lifts liquid using the same principle—but does so at a speed that would make nature envious.
The metal, revealed in an upcoming issue of Applied Physics Letters, may prove invaluable in pumping microscopic amounts of liquid around a medical diagnostic chip, cooling a computer's processor, or turning almost any simple metal into an anti-bacterial surface.
"We're able to change the surface structure of almost any piece of metal so that we can control how liquid responds to it," says Chunlei Guo, associate professor of optics at the University of Rochester. "We can even control the direction in which the liquid flows, or whether liquid flows at all."
Guo and his assistant, Anatoliy Vorobyev, use an ultra-fast burst of laser light to change the surface of a metal, forming nanoscale and microscale pits, globules, and strands across the metal's surface. The laser, called a femtosecond laser, produces pulses lasting only a few quadrillionths of a second—a femtosecond is to a second what a second is to about 32 million years. During its brief burst, Guo's laser unleashes as much power as the entire electric grid of North America does, all focused onto a spot the size of a needlepoint, he says.
The wicking process, which on Guo's metal moves at a quick one centimeter per second speed against gravity, is very similar to the phenomenon that pulls spilled milk into a paper towel or creates "tears of wine" in a wineglass—molecular attractions and evaporation combine to move a liquid against gravity, says Guo. Likewise, Guo's nanostructures change the way molecules of a liquid interact with the molecules of the metal, allowing them to become more or less attracted to each other, depending on Guo's settings. At a certain size, the metal nanostructures adhere more readily to the liquid's molecules than the liquid's molecules adhere to each other, causing the liquid to quickly spread out across the metal. Combined with the effects of evaporation as the liquid spreads, this molecular interaction creates the fast wicking effect in Guo's metals.
Adding laser-etched channels into the metal further enhances Guo's control of the liquid.
"Imagine a huge waterway system shrunk down onto a tiny chip, like the electronic circuit printed on a microprocessor, so we can perform chemical or biological work with a tiny bit of liquid," says Guo. "Blood could precisely travel along a certain path to a sensor for disease diagnostics. With such a tiny system, a nurse wouldn't need to draw a whole tube of blood for a test. A scratch on the skin might contain more than enough cells for a micro-analysis."
Guo's team has also created metal that reduces the attraction between water molecules and metal molecules, a phenomenon called hydrophobia. Since germs mostly consist of water, it's all but impossible for them to grow on a hydrophobic surface, says Guo.
Currently, to alter an area of metal the size of a quarter takes 30 minutes or more, but Guo and Vorobyev are working on refining the technique to make it faster. Fortunately, despite the incredible intensity involved, the femtosecond laser can be powered by a simple wall outlet, meaning that when the process is refined, implementing it should be relatively simple.
Guo is also announcing this month in Physical Review Letters a femtosecond laser processing technique that can create incandescent light bulbs that use half as much energy, yet produce the same amount of light. In 2006, Guo's team used the femtosecond laser to create metal with nanostructures that reflected almost no light at all, and in 2008 the team was able to tune the creation of nanostructures to reflect certain wavelengths of light—in effect turning almost any metal into almost any color.
Source: University of Rochester (news : web)
Nov 21, 2006 |
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Get it?
it really is that simple.
And Shotman, because you won't be able to exert this effect over a large enough scale without adding more energy than you take out.
put the anti bacterial etching on all doorknobs, handles (especially shopping carts), and any faucets and i wont even ask for any reward for the idea - just living in that world will be reward enough.
Because it takes energy to remove the water from the channel. In trees the water is removed by evaporation which takes energy.
Ethelred
Capillary. Venturi is the acceleration of a moving gas when its path is restricted.
Though I doubt that is why Parsec gave you a one.
I don't like solo ones without explanation. Its intellectual cowardice. A one that is a single vote after many others doesn't bother me as usually others have expressed something resembling a rebuttal and another would look a 'me too' post. Its that first one that is really annoying.
Ethelred
They mention how a paper towel "pulls" a fluid into it, but you wouldn't try to use a paper towel to pump water up a hill. It just absorbs water untill it is full.
Or has Rosie been keeping a miraculous secret from us for all these years?
"Bounty: The Perpetual Quick Picker-Upper"
Water is repelled by wax and attracted to glass. A thin tube or in this case a surface channel of a material that attracts water, which includes most if not all metals, will draw water into it.
The water can only be removed by an expenditure of some kind of energy. Squeezing in the case of a towel, evaporation in the case of trees.
The technique for creating the channels seems a bit impractical but maybe it can managed. The real problem I see is that it won't have much real world use. Handling will erode the channels and dirt or even water spots will fill them.
Its not a solution looking for a problem. Its a solution looking for a problem that won't destroy the solution. The companion article about using the laser on a light bulb at least has the surface change in a controlled environment so the change might be permanent enough to be useful. I have my doubts on that because tungsten evaporates in light bulbs.
Ethelred
Transpiration not capillary action draws water up trees. The height capillary action can draw water up a tube is dependent on its diameter. This sets an upper limit of about 1m for the thinnest tube.
I'm surprised at this simple error in the introduction to this article.
Transpiration is dependent on capillary action. That is why the diameter of the tube has to be that size or smaller. If it was larger the only thing pushing the water up the tube would be air pressure and that is limited to 33 feet. Without capillary forces trees could be at most 10 meters tall.
Ethelred
You're right, my bad.
Venturi effect is the change in stored energy when a fluid (gas or liquid) reaches a change in pressure due to effusion through a medium. Capillary action is the draw of a fluid through a medium due to a mismatch in pressures at the point of origin vs the end point.
And solo 1's without explanation are ridiculous.
I'm sorry to disagree but the mechanism behind transpirational water transport is transpirational pull and osmotic root presure, which has nothing to do with capillary action.
The pressure is not enough. Try looking at what YOU wrote. The narrow tubes are there because that is what is needed for capillary action. Capillary forces DON'T pump water through the tube, they just draw it into the tube at the most. The things you mention are what gets it out of the tube.
Osmosis in the tendency for water with a low solute concentration to move into a zone with a higher concentration thus diluting it, this normally occurs across a permeable membrane. But if the pressure is high enough on the high concentration side of the membrane water will move in the reverse direction. A 300 foot column of water has a fairly high pressure unless the column is narrow enough to create a capillary effect.
Evaporation (transpiration)is can only produce a low pressure area which is, at best, zero pressure. Nothing really sucks water. Water is PUSHED by pressure of the osmotic forces and atmospheric pressure towards the low pressure zone in the leaves or, in the case where this 33 foot limit was discovered, the top of the mine. Maximum height for lowering pressure, so called sucking, is 33 feet as that is as high as the atmospheric pressure can push a column of water. 33 feet of water produces one atmosphere of pressure thus the 33 foot limit.
So transpiration is only good for 33 feet. Osmotic pressure has limits as well but frankly I don't know how much pressure a solute differential can generate. I doubt that is enough to overcome 300 feet of solute heavy water. If so, then your right but then why are the tubes actual capillaries?
The fact that the tubes are so narrow shows capillary action is involved. Its certainly inherent in the width of the tubes that it will be involved.
http://en.wikiped...y_action
http://en.wikiped...piration
http://en.wikiped...pirational_pull
That last one shows what I was yammering on about. I wrote that on basic principles and then checked to see if I was full of it. Basic principles only get you so far, especially when you don't have a degree. Key paragraph is:
Which is what I was saying though you might not have seen it that way. Capillary effects, which are generated by surface tension or, more basically, the tendency for water to adhere to other compounds, can only work WITHIN the tube and can't get the water out of the tube(to bloody many commas but I think that parses). Which is why I said:
Ethelred
Surface tension is cohesion, the tendency for water to stick to water. Adhesion is the tendency for water to stick to non-water substances. Capillary action is a combination of both.
"A common misconception is that water moves in xylem by capillary action"
I'm surprised at this simple error in the introduction to this article.
To give an example:
'Boats float because they displace more water than they weigh.'
Its true as far it goes but it not right. Boats float because there is more total force pushing up on the boat then there is pushing down on the boat. However in the first way the math is easier and the result the same. Until you need to check the stress on the hull.
Ethelred
http://nanochemic...spot.com
Are you ever going to contribute to a discussion? Or is this posting of irrelevant links with not a word to show WHY all you are ever going to do? About all I can say for your posts is that its not actually spam.
Ethelred