Water-hating knife slices droplet in half

To quote Jacob Aron reporting for the New Scientist blog, “Cutting a drop of water in half may sound like the kind of impossible task given to heroes of folk tales. You don't need a magic knife, though – just one that really, really hates liquid (water).”

Recently published work led by graduate student Ryan Yanashima and associate professor Mark Hayes in the Department of Chemistry and Biochemistry in ASU’s College of Liberal Arts and Sciences, and initiated by professor Antonio Garcia in ASU’s School of Biological and Health Systems Engineering, has shown that a superhydrophobic knife can create two cleanly separated drops of water, with potential applications in biomedical research.

Watch how a drop of water can be separated in this 10-second YouTube video.

By creating two droplets from a single drop under very controlled conditions, a variety of micro and nano techniques can be used to study the contents of the drop or produce very small amounts of a rare molecule or biological structure. For example, in biomedicine there can be reason to isolate a single, rare cell (such as a cell suspected of being cancerous) and perform a series of analyses to detect what exactly is in the cell that makes it different from others.  

“Isoelectric focusing is a means of separating and concentrating proteins in a sample, and we are able to show this could be done on the scale of, and within, a single water droplet," explains Yanashima. "Our work on drop splitting is a follow-up to show how one could reliably split the sample droplet so that we don't have undesired mixing within the droplet, which would preserve the separated contents (proteins, as an example) contained within.”

“Scientists in general have been trying to understand cells and the details of how they function down to the molecular level, and they have also been working on ways to separate every molecule in a liquid," says Garcia. "We hope that our work stimulates more creative ideas on how to achieve these goals and perhaps create new technologies that we cannot yet imagine.”

“Our work points to fundamental physical advances being interesting and popular, yet practically applicable to biotechnology problems of immediate impact,” explains Hayes.