Chip mixes droplets faster

Researchers are working to make entire chemistry labs on omputer chip-size pieces of glass or plastic, which promises to automate, speed, and shrink the samples needed for testing and sensing.

It is a challenge, however, to quickly mix tiny amounts of fluids because samples get more molasses-like as they get smaller. A team of researchers from Duke University has improved a method to mix droplets smaller than a nanoliter, or billionth of a liter. The method makes it possible to mix a pair of merged nanoscale-size droplets in less than two seconds rather than the 90 seconds ordinarily needed.

The team carried out the quick mixing on a surface connected to a two by four array of electrodes. They used electrowetting -- a method that uses electricity to move liquids on a surface -- to work out paths that would cause the droplets to mix most efficiently.

The method could eventually be used on labs-on-a-chip that require only small amounts of samples like blood to run tests. It could also be used in a wide variety of chemistry applications including DNA sequencing, according to the researchers.

An automated, self-contained lab-on-a-chip using the technology could be ready for practical use in one to two years, according to the researchers. The work appeared in the September 12, 2003 issue of Lab on a Chip.