The gas permeation micropumping mechanism moves miniature drops of fluid to specific locations in a microfluidic lab-on-a-chip device.
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A micropump that pushes lab samples through a credit-card-sized lab-on-a-chip is keeping up with the race to develop smaller, faster, and cheaper diagnostics. The tiny three-
layered pump could accelerate the time it takes for patients to receive test results. Instead of waiting for weeks, the patient might be able to get results almost immediately.
“The general motivation for our work is the development of lab-on-a-chip devices that can replace large, cumbersome laboratory equipment with a small portable benchtop and point-of-care instrumentation,” says Mark Eddings, a bioengineering graduate student at the University of Utah (Salt Lake City).
A micropump is a necessary component that manipulates the samples and reagents required for a medical test. Although some researchers have developed pumps that require sophisticated manufacturing and materials, others have designed low-cost silicone-rubber-based pumps, which are on the path to commercialization, according to Eddings. “Our micropump uses similar manufacturing and materials as these groups,” he says. “However, we exploit the permeable properties of the silicone rubber, polydimethylsiloxane (PDMS), to push and pull fluid to specific locations within our lab-on-a-chip.”
The pump is made of three layers of PDMS. The top fluid layer contains both the wells where the sample is placed and microchannels through which the sample flows. The thin middle layer allows only the passage of gas, not liquid. The bottom layer has inlets and channels through which air pressure or a vacuum is applied. The air pressure or vacuum respectively pushes or pulls air through channels and transmits pressure or suction through the middle layer. This pushes or draws fluids through the upper-layer channels. After flowing through the channels, the liquid is pushed into test chambers where the sample is mixed with the chemicals or antibodies needed for the test.
The PDMS-based gas-permeation pump isn't a stand-alone device; it must be incorporated into a system. About the size of a wallet, an outside device that has air pressure or a vacuum to run the micropumps would operate the lab-on-a-chip. The chip is like a credit card that fits into the wallet.
Eddings notes that practical applications of the micropump are mainly in point-of-care diagnostics and biochemical testing. The researchers at Utah have demonstrated the micropump's ability to generate controlled flows. That could lead to future drug-delivery applications.
“We're also looking at integrating the micropump into some of our own lab-on-a-chip applications for genotyping and mutation scanning of DNA,” adds Eddings. “A number of microfluidics research groups expressed interest in possible collaborations when the work was presented at a recent conference in Japan, but we are continuously looking for industry and academic partnerships.”
A paper on the work by Eddings and Bruce Gale, assistant professor of mechanical engineering at Utah, can be found in the November issue of the Journal of Micromechanics and Microengineering. Funding was provided by the university's Center for Biomedical Fluidics and the National Science Foundation.