By Roland Piquepaille
Researchers from the University of Texas M.D. Anderson Cancer Center have devised a new programmable biochip which cn manipulate nanoliter droplets. In this article, Technology Research News says that this biochip "uses an array of electrodes to place water droplets on a surface, insert substances into the droplets, and move and merge the droplets." The device, which has no moving parts, could help to identify pathogen agents in the field. A prototype should be ready by the end of the first half of 2004.The droplets, which range from 20 to 500 microns in diameter and 0.5 to 65 nanoliters in volume, serve as carriers for samples, contaminants, chemical reagents, viral and genetic material, and cells. A nanoliter is one millionth of a milliliter, and there are about 5 milliliters to a teaspoon.
The device makes it possible to automate biochemical analysis and detection to, for instance, identify pathogens in the field. The biochip and its computer controller could eventually be miniaturized and incorporated into portable medical, biological and chemical diagnostic devices, according to the researchers.
The biochip contains a 32-by-32 array of electrodes. Water droplets suspended in a thin film of liquid hydrocarbon can be moved and merged by sending electrical current to the right sequence of electrodes.
Here is a picture of this biochip, shown as it is loaded with fluorescent dye, moves and mixes droplets to perform biological and medical tests (Credit: M. D. Anderson Cancer Center).
Even if the researchers plan to have a protoype ready by the ned of the first half of 2004, they don't expect to have a miniaturized, fully-automated device available for field testing before two years.
The research work has been published in the first issue of Lab on a Chip in 2004. Here is the abstract.
We describe the manipulation of aqueous droplets in an immiscible, low-permittivity suspending medium. Such droplets may serve as carriers for not only air- and water-borne samples, contaminants, chemical reagents, viral and gene products, and cells, but also the reagents to process and characterise these samples. We present proofs-of-concept for droplet manipulation through dielectrophoresis by: (1) moving droplets on a two-dimensional array of electrodes, (2) achieving dielectrically-activated droplet injection, (3) fusing and reacting droplets, and (4) conducting a basic biological assay through a combination of these steps. A long-term goal of this research is to provide a platform fluidic processor technology that can form the core of versatile, automated, micro-scale devices to perform chemical and biological assays at or near the point of care, which will increase the availability of modern medicine to people who do not have ready access to modern medical institutions, and decrease the cost and delays associated with that lack of access.
Sources: Eric Smalley, Technology Research News, February 25 - March 3, 2004; Issue 1 of Lab on a Chip, 2004
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