As medical researchers and engineers try to shrink diagnostics to fit in a person's pocket, one question is how to easily move and mix small samples of liquid.
University of Washington researchers have built and patented a surface that, when shaken, moves drops along certain paths to conduct medical or environmental tests.
"This allows us to move drops as far as we want, and in any kind of layout that we want," said Karl Bhringer, a UW professor of electrical engineering and bioengineering. The low-cost system, published in a recent issue of the journal Advanced Materials, would require very little energy and avoids possible contamination by diluting or electrifying the samples in order to move them.
The simple technology is a textured surface that tends to push drops along a given path. It's inspired by the lotus effect a phenomenon in which a lotus leaf's almost fractal texture makes it appear to repel drops of water.
"The lotus leaf has a very rough surface, in which each big bump has a smaller bump on it," Bhringer said. "We can't make our surface exactly the same as a lotus leaf, but what we did is extract the essence of why it works."
The UW team used nanotechnology manufacturing techniques to build a surface with tiny posts of varying height and spacing. When a drop sits on this surface, it makes so little contact with the surface that it's almost perfectly round. That means even a small jiggle can move it.
Researchers used an audio speaker or machine to vibrate the platform at 50 to 80 times per second. The asymmetrical surface moves individual drops along predetermined paths to mix, modify or measure their contents. Changing the vibration frequency can alter a drop's speed, or can target a drop of a certain size or weight.
"All you need is a vibration, and making these surfaces is very easy. You can make it out of a piece of plastic," Bhringer said. "I could imagine this as a device that costs less than a doll
|Contact: Hannah Hickey|
University of Washington