IN THE PALM OF YOUR HAND: ELECTRICITY AND MAGNETISM DRIVE NEW APPROACH TO MICROFLUIDICS

FAYETTEVILLE, Ark. - A team of University of Arkansas researchers has discovered an effective way to move small amounts of fluid around miniscule channels. Their work may one day lead to the creation of a lab on a chip, or a hand-held device, which could be used in medicine, research and industry to provide on-the-spot diagnosis, experimentation and monitoring.

Ingrid Fritsch, associate professor of chemistry and biochemistry, will report her team’s findings at a symposium on recent advances in microfluidics at 2:30 p.m. Thursday, April 5, at the 221^st meeting of the American Chemical Society in San Diego.

Moving small fluid volumes down hair-width channels is a difficult problem for the researchers who work with them. Current methods used to resolve this problem include electrokinetic pumping, mechanical pumping, and centrifugal force, which all have drawbacks, including moving parts and the need for high voltages.

"The method we are using has a larger fraction of the positive features (desired in a dynamic microfluidics system) than the other techniques," Fritsch said.

The system has low voltage requirements, no moving parts or valves, and can be used with a variety of channel materials and aqueous and non-aqueous solvents.

"We expect that this method will also allow mixing and stirring in ultra-small volumes of solution," Fritsch said.

Fritsch and her team apply a technique called magnetohydrodynamics (MHD) to microfluidics. As early as 1832, scientists knew that they could pump water by applying a voltage to it and creating a magnetic field. This phenomenon has been used to understand plasmas in astrophysics, control plasmas in nuclear fusion, generate electrical power, pump liquid metal coolants, and control the quality of electroplating, but only recently has been applied to microfluidics.

Although a few researchers have shown how MHD can be applied to microfluidics, they are beset by problems. Fritsch eliminated those barriers by using charged molecules to carry the current through the system.

Using MHD, researchers could design a device with electrodes and magnets in different geometries to control the flow of fluids. The fields’ respective strengths determine the flow rate. And if one of the fields is reversed, the flow reverses, without need of mechanical manipulation. The researchers could also create a vortex and control the mixing of compounds they want to study.

Fritsch’s team is applying the MHD microfluidics approach to ELISAs, commonly used to detect proteins in solution. ELISAs are currently a popular method used for clinical diagnostics.

"The currents and magnetic fields are all appropriate magnitudes suitable for a chip-based system," Fritsch said, "so it could potentially be a hand-held device."

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Editor’s note: Ingrid Fritsch will be at the Hyatt Regency San Diego during the ACS meeting. The hotel phone number is (619) 232-1234.