'Laboratories on a chip' get super-small, super-smart plumbing

November 14, 2002

If a crime scene yields only a single drop of blood as evidence, how can a forensics lab perform the dozens of necessary tests on it? What if a doctor finds a suspicious bacterium, but a patient can't wait for the days needed to grow a large colony for testing?

University of Rochester researchers are working on a new way to move and distribute microscopic amounts of fluid around a chip, essentially mimicking the work of scientists testing dozens of samples in a laboratory. The research is in response to a growing demand for "laboratories on a chip," programmable devices that automatically perform the multiple tests on much smaller amounts of material--on site and more efficiently than ever before. Researchers around the world are already working to develop chips that will allow instant glucose monitoring, DNA testing, drug manufacturing, and environmental monitoring.

In order to work, all of these chips need some sort of plumbing system to move liquid. Thomas B. Jones, professor of electrical engineering, and his team have developed a way to use the electrostatic attraction of water to electric fields, called dielectrophoresis, to divide a single drop of water into dozens of incredibly tiny droplets and move them to designated sites on a chip. The droplets can be mixed with specialized testing chemicals or biological fluids, or positioned for diagnostic tests with lasers or electrical pulses. Essentially, any laboratory test that can be shrunk to fit on a chip will be able to be serviced by the new plumbing system.

"Microchemical analysis is a rapidly advancing field, but while there are ways to test minuscule liquid volumes, no one has yet come up with a practical way to dispense and move these liquid samples around a chip," says Jones. "We're hoping to change all that. We've been able to take a single drop of water and split it up into as many as 30 droplets of specific sizes, route them around corners, send different droplets to different points on a chip and even mix different drops together." Other microfluidic schemes use tiny channels and passages machined into substrates, but these are not only hard to make, but the pressure needed to move the fluid inside means that the slightest defect in fabrication could produce leaks. Jones' system uses narrow electrodes etched onto glass--so thin that they're almost invisible to the naked eye. AC voltage at about 60 kilohertz is applied to the electrodes and the resulting electrical force causes a "finger" to project from the drop. The finger stretches out along the electrode until it reaches the end, sort of a widened cul-de-sac. When the voltage is then switched off, the surface tension of the water itself pulls about half of the finger of water back toward the initial drop while half is left to form the droplets. This cul-de-sac can be quite a distance away across the chip--close to a centimeter in Jones' laboratory--and the path to it can even take sharp turns with ease.

Mixing different droplets together is as simple as setting the cul-de-sacs of two paths next to each other and then changing the electrical connections so that the droplets are attracted toward each other. To produce multiple droplets from a single finger, Jones widens the wires at certain areas along the path, making the finger bulge in that area and accumulating a droplet when the finger retracts.

In the same way that miniaturization changed computers from room-sized machines to pocket calculators, a similar change is coming to chemistry and the biological sciences. Familiar laboratory procedures are being automated and scaled down to the size of microchips. Some companies are even looking to such chips to manipulate and investigate individual cells, while others could benefit from a chip's ability to carry out possibly hundreds of tests on a new drug in just minutes. As the field expands, scientists are finding more uses for such micro-labs.

Eventually, other liquids will be able to be manipulated as well. Jones' team did some preliminary work on antifreeze and noted that while it stretched out similar fingers, the fingers always fully retracted to the mother drop. The team is now working on ways to control both water and other liquids with more finesse.

This research has received support from the National Science Foundation, the Japan Society for the Promotion of Science, the National Institutes of Health, the Infotonics Technology Center, and the Center for Future Health at the University of Rochester.
-end-


University of Rochester

Related Water Articles from Brightsurf:

Transport of water to mars' upper atmosphere dominates planet's water loss to space
Instead of its scarce atmospheric water being confined in Mars' lower atmosphere, a new study finds evidence that water on Mars is directly transported to the upper atmosphere, where it is converted to atomic hydrogen that escapes to space.

Water striders learn from experience how to jump up safely from water surface
Water striders jump upwards from the water surface without breaking it.

'Pregnancy test for water' delivers fast, easy results on water quality
A new platform technology can assess water safety and quality with just a single drop and a few minutes.

Something in the water
Between 2015 and 2016, Brazil suffered from an epidemic outbreak of the Zika virus, whose infections occurred throughout the country states.

Researchers create new tools to monitor water quality, measure water insecurity
A wife-husband team will present both high-tech and low-tech solutions for improving water security at this year's American Association for the Advancement of Science (AAAS) annual meeting in Seattle on Sunday, Feb.

The shape of water: What water molecules look like on the surface of materials
Water is a familiar substance that is present virtually everywhere.

Water, water everywhere -- and it's weirder than you think
Researchers at The University of Tokyo show that liquid water has 2 distinct molecular arrangements: tetrahedral and non-tetrahedral.

What's in your water?
Mixing drinking water with chlorine, the United States' most common method of disinfecting drinking water, creates previously unidentified toxic byproducts, says Carsten Prasse from Johns Hopkins University and his collaborators from the University of California, Berkeley and Switzerland.

How we transport water in our bodies inspires new water filtration method
A multidisciplinary group of engineers and scientists has discovered a new method for water filtration that could have implications for a variety of technologies, such as desalination plants, breathable and protective fabrics, and carbon capture in gas separations.

Source water key to bacterial water safety in remote Northern Australia
In the wet-dry topics of Australia, drinking water in remote communities is often sourced from groundwater bores.

Read More: Water News and Water Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.