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March 29, 2010

Laser makes silicon pump liquid uphill

Work could pave way for more efficient cooling systems for computers

silicon chip
Chunlei Guo, associate professor of optics, and research assistant Anatoliy Vorobyev
demonstrate that by carving intricate patterns in silicon with extremely short,
high-powered laser bursts, they can induce liquid to climb to the top of a silicon chip


Researchers at the 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 as if it were 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, the same researchers proved that the phenomenon was possible with metal, but extending it to silicon could have some important implications. For instance, Guo says, 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,” says Michael Scott, a professor of computer science at the University, who is not involved in this research.

Chunlei Guo

Computer chips are essentially wafers of silicon covered with billions of microscopic transistors that communicate by sending electrical signals through metal wires that connect them. As technological innovations make it possible to pack astounding numbers of transistors on small pieces of silicon, computer processing speeds could increase substantially; however, the electrical current constantly surging through the chips creates a lot of heat, Scott says. If left unchecked, the heat can melt or otherwise destroy the chip components.

Most computers these days are cooled with fans. Essentially, the air around the circuit components absorbs the heat that’s generated, and the fan blows the hot air away from the components. The disadvantages are that cold air cannot absorb much heat before becoming hot, making fans ineffective for faster processors, and fans are noisy.

For these reasons, many companies have been eager to investigate the possibility of using liquid as a coolant instead of air. Liquids can absorb far more heat and transmit heat much more effectively than air. So far, designers have not created liquid cooling systems that are cost-effective and energy efficient enough to become widely used in economical personal computers. 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 contribute greatly to the design of future cooling systems.

Sights—and sounds—of spring

Conference aims to build ‘stronger community’

On Monday, April 5, more than 100 administrators, trustees, faculty, staff, alumni, and community members will gather to discuss programs and policies related to issues of diversity and inclusion on Rochester’s campuses.

Be counted: Census 2010

Fill out the 10 questions on your census questionnaire when it arrives in your mailbox and you will help the Rochester region get its fair share of funding.

Yellowjackets Finish Fourth

Rochester finished fourth in the nation, the team’s best finish since 2004.

Taubman takes reins at medical school

Mark Taubman became the 10th dean of the School of Medicine and Dentistry earlier this month.

The University’s ‘eyes and ears on the ground’

“We act on behalf of the University—the institution and all of our affiliates—and we advocate on their behalf at all levels of governments,” says director Josh Farrelman. “We advance their missions, their priorities, their projects. We’re their eyes and ears on the ground.”

Berk returns as CEO

Bradford Berk returned March 1 from a serious injury—a cervical fracture and severe spinal cord injury—to assume full responsibilities as CEO of the Medical Center and the University’s senior vice president for health sciences.

New center to focus on early stage clinical research

The Center for Human Experimental Therapeutics represents the first university-based program focused on accelerating the development of novel medical therapies.

Staff Saluted for Outstanding Service

The recipients of this year’s staff awards are being honored for a long list of contributions to the University, including dedication, talent, and enthusiasm.

Virtual work space for academics promises greater access to research

“It’s a win-win relationship,” says Suzanne Bell, the librarian charged with introducing the system to the University community.

University intercessors examine issues through many lenses

Typically, intercessors assist with relationship problems among peers or with supervisors, harassment or discrimination concerns, diversity issues, and workplace accommodation needs.

First Presidential Diversity Awards presented

The first recipients of the Presidential Diversity Awards are members of the Latino Professional Alliance; the David T. Kearns Center; and John Hansen, associate dean for admissions for the School of Medicine and Dentistry.

College Diversity Roundtable launches second campus climate survey

The anonymous survey aims to evaluate undergraduates’ past and current experiences with issues of diversity, including race, ethnicity, gender, sexual orientation, religion, and disability.

Contest helps raise eco-awareness

Students, with the help of recycling coordinator Amy Kadrie, organized several events during the competition to raise awareness about RecycleMania and its goals for reducing campus waste.

ArtAwake brings historic building back to life

Constructed in 1924, the Monroe County Savings Bank at 35 State St. in downtown Rochester was designed to convey strength and security. Eighty-six years later, a shimmer of the bank’s past glory will be brought to life as ArtAwake 2010 turns the former financial institution into an art gallery and music hall.

Forum will examine impact of political rhetoric

The Institute for the Interdisciplinary Study of Political Rhetoric, Media and Public Opinion will host a forum April 1 to 3 in the Hawkins-Carlson Room to examine the increasing prominence and influence of political memoirs, specifically the books’ impact on the 2008 presidential election.

United Way campaign in final weeks

As of March 24, the University community had raised $757,000–nearly 60 percent of the goal.

How I Live United