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Knife cleanly cuts water droplets

Two professors and a student spent months of trial and error developing a knife that can cleanly cut droplets of water.

Chemistry graduate student Ryan Yanashima said this superhydrophobic knife repels water so much so that the water rolls off the blade’s surface and will open doors for further analysis within the biotechnology industry and patient diagnosis.

Yanashima, one of the knife’s developers, began researching and gathering data to develop the knife in February 2011 and discovered that only copper and zinc effectively cut through water.  She finished the experiment in April 2011.

The superhydrophobic knife creates a foundation for larger works in science, Yanashima said.

Yanashima and her collaborators intend to help lead the way for more in-depth analysis of water samples, particularly in medical diagnosis.

“Most biological samples are going to be water-based, so the superhydrophobic surfaces help for many different things,” she said.  “Also, it is a lot easier to dissolve a protein in a water droplet than, for example, an oil droplet, so this will help in our ultimate goal of the analysis of proteins or cells.”

The ability to dissect a sample with the knife could assist in determining what’s wrong with a patient by allowing close analysis of bodily fluids, such as blood or urine, Yanashima said.

Project co-developer Mark Hayes, a chemistry and biochemistry professor, said the knife can have important and practical uses in the real world, despite its beginnings as a simple concept.

“It really is basic physics when you get right down to it,” Hayes said. “Underneath that is a very serious assessment of the way water reacts with superhydrophobic surfaces.”

The experiment is part of a larger scientific study conducted by Hayes and Antonio Garcia, co-developer and professor in the Ira A. Fulton Schools of Engineering.

By creating smaller samples of water, the professors intend to aid field analysis, Garcia said.

“(Hayes) does a lot of work in bio-analysis and trying to do analysis of smaller and smaller amounts of material, which is really important when you are trying to understand everything that’s going on in a cell,” Garcia said.

The entire process took about a year and a half, culminating in the Sept. 24 publication of a research paper titled “Cutting a Drop of Water Pinned by Wire Loops Using a Superhydrophobic Surface and Knife.” The paper is available in the open-access journal PLOS ONE.

The group’s goal for the invention is to show the unique interactions water can have with other materials.

Yanashima created a video demonstrating the process of a droplet being cut in half by the knife. The video has received many views from around the world, Garcia said.

“All we had to do is sit back and let it go viral,” he said.  “Google tells us (it received) about 300,000 hits in Spanish, 200,000 in Portuguese, (and) … about 100,000 or so in Italian.”


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