Professor Chunlei Guo’s lab at the Robert B. Goergen Hall for Biomedical Engineering and Optics announced the first successful initiative in making liquid climb vertically up a surface without the use of any mechanical forces.

This research was funded primarily by the Air Force Office of Scientific Research and in part by the National Science Foundation, and published in the journal Optics Express. In their paper, Guo and his assistant Anatoliy Vorobyev discuss how this discovery can be attributed to the treatment of silicon plates with incredibly fast femtosecond lasers.

Extremely short, high-powered pulses delivered from such lasers have the ability to create tiny structures in the silicon. These structures increase the attraction of water molecules to silicon by so much that neighboring water molecules compete to come in contact with the silicon.

Consequently, the bonds holding water molecules together are overcome and the molecules climb upward over one another, opposing gravity at the rate of 3.5 centimeters per second.

Moreover, while the femtosecond laser bursts are capable of creating intricate patterns in silicon precisely, they leave its surface undestroyed and relatively smooth to the touch.
Guo envisions this discovery paving the way for more effective cooling systems, thereby advancing the design of faster processors.

Most modern computer chips generate a tremendous amount of heat. Current cooling systems primarily use fans, and since air circulation absorbs little heat, these systems are noisy and highly inefficient. This limits processing speed and can endanger chip components.

One possible solution to this problem that is gaining momentum is the use of liquids as a coolant. Liquids are capable of absorbing heat much more efficiently than air, but they must be circulated in order to do this.

Guo has high hopes for his new technique as a way to accomplish this circulation, which would allow for a much greater absorption of heat.

He has made several other contributions to the field of femtosecond lasers as well, eliciting their potential to alter metal surface structures, making brighter, more efficient sources of light, colorizing metals and structuring titanium.

‘In the past few years, my lab has developed a number of techniques that dramatically change material properties of metals,” Guo said. ‘That motivated us to make liquids flowing uphill on silicon, and we have been working on this project over the past half a year.”
He also mentioned potential applications of this research in microfluidics, chemical and biological sensors and lob-on-chip technology.

Rath is a member of the class of 2012.

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