From PESWiki

Page first featured March 18, 2010

Liquid flows uphill on a treated silicon surface.
Credit: Press Office at University of Rochester

Researches Chunlei Guo and Anatoliy Vorobyev at the Institute of Optics at the University of Rochester have devised a process in which a special high-power laser etching on the surface of silicon makes liquid flow vertically upward along the silicon surface, overcoming the pull of gravity, without pumps or other mechanical devices.

Using a short-pulse, high-intensity laser, they have created tiny grooves in silicon that exhibit strong capillary action — they quickly wick water along, even against gravity. Prior to silicon, they were using this approach on metal surfaces.

Because the same adhesion that causes the fluid to climb the substrate would also prevent it from easily leaving the substrate at the top, such a system would not be plausible for feeding a turbine to harness energy.

The primary application of the technology would be for evaporative cooling systems, probably for the computer industry.

Because the etching makes the surface capture photons, making it pitch black, another application might be on the collecting surface of solar thermal systems.

Official Websites

• http://www.optics.rochester.edu
  • Ultra-powerful Laser Makes Silicon Pump Liquid Uphill with No Added Energy (University of Rochester News; March 16, 2010)
  • Chunlei Guo, the Professor heading the project at the University of Rochester.

Press Release

via Ultra-powerful Laser Makes Silicon Pump Liquid Uphill with No Added Energy (University of Rochester News; March 16, 2010)

Researchers at the University of Rochester’s Institute of Optics have discovered a way to make liquid flow vertically upward along a silicon surface, overcoming the pull of gravity, without pumps or other mechanical devices.

In a paper in the journal Optics Express, professor Chunlei Guo and his assistant Anatoliy Vorobyev demonstrate that by carving intricate patterns in silicon with extremely short, high-powered laser bursts, they can get liquid to climb to the top of a silicon chip like it was being sucked through a straw.

Unlike a straw, though, there is no outside pressure pushing the liquid up; it rises on its own accord. By creating nanometer-scale structures in silicon, Guo greatly increases the attraction that water molecules feel toward it. The attraction, or hydrophile, of the silicon becomes so great, in fact, that it overcomes the strong bond that water molecules feel for other water molecules.

Thus, instead of sticking to each other, the water molecules climb over one another for a chance to be next to the silicon. (This might seem like getting energy for free, but even though the water rises, thus gaining potential energy, the chemical bonds holding the water to the silicon require a lower energy than the ones holding the water molecules to other water molecules.) The water rushes up the surface at speeds of 3.5 cm per second.

Yet the laser incisions are so precise and nondestructive that the surface feels smooth and unaltered to the touch.

In a paper a few months ago in the journal Applied Physics Letters, the same researchers proved that the phenomenon was possible with metal, but extending it to silicon could have some important implications. For instance, Guo said, this work could pave the way for novel cooling systems for computers that operate much more effectively, elegantly, and efficiently than currently available options.

“Heat is definitely the number one problem deterring the design of faster conventional processors,” said Michael Scott, a professor of computer science at the University, who is not involved in this research.

PES Coverage

• 
  Featured: Cooling / Capillary Action > NEW: U of Rochester's laser-etching
  Laser-etched silicon draws fluid upward – ideal for evaporative cooling, not for perpetual motion - Researches at the University of Rochester have devised a process in which a special high-power laser etching on the surface of silicon makes liquid flow vertically upward along the silicon surface, overcoming the pull of gravity, without pumps or other mechanical devices. (PESN; March 18, 2010) (Comments)
  

In the News

• University of Rochester researchers coax liquid to climb silicon chip - This new technique of cooling has not been implemented in a prototype as yet, though Guo considers the ability of silicon to pump its own coolant to have ... (TechGadgets.in; March 18, 2010)

• Ultra-powerful laser makes silicon pump liquid uphill with no added energy - Although Guo's discovery has not yet been incorporated into a prototype, he thinks that silicon that can pump its own coolant has the potential to ... (Sify; ‎Mar 17, 2010‎)

• Researchers Create Silicon that Pumps Water Vertically with no Moving Parts - A pair of researchers at the University of Rochester has discovered a new method that may one day lead to a very efficient and effective cooling system for processors. (DailyTech; March 17, 2010)

• Ultra-powerful Laser Makes Silicon Pump Liquid Uphill with No Added Energy – Speculates: "Water moves uphill at 0.078 mile per hour, forever with no extra energy added! Close the system add a little electrical generator spun by the water when it falls after collecting in a pool at the top… I don’t see why this couldn’t be made into something that would qualify as the perpetual motion machine." (Xenophilius; March 16, 2010)

• For Cooler Chips, Follow the Grooves - what if water or other liquid could be circulated on the silicon itself? That might make for better cooling, and faster chips. (NY Times; March 15, 2010)

Contact

Chunlei Guo, the Professor heading the project at the University of Rochester.

U of R story contact: Alan Blank
email: alan.blank@rochester.edu
phone: 585-275-2671

See also

• Directory:Capillary Action Engines (which this is not)
• Directory:Refrigeration

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