A new sensor could quickly and cheaply detect mercury and other toxic metals in rivers, lakes and fish. The sensor relies on an analysis machine that would cost a few hundred dollars to buy, the sensor's creators estimated, compared to conventional machines' millions. Researchers hope cheap testing will encourage groups to check waterways more extensively, so fish will be safer for consumption.
"With this technology, it will be possible to conduct tests on a much larger scale in the field, or even in fish before they are put on the market," one of the sensor's developers, a graduate student in materials science at the Massachusetts Institute of Technology named Eun Seon Cho, said in a statement.
The sensor detects methyl mercury, a common pollutant in waterways, especially well; in high concentrations, the pollutant can damage the developing nervous systems of young children and unborn fetuses. Currently, the U.S. Environmental Protection Agency recommends how much certain mercury-heavy seafood, such as albacore tuna, kids and pregnant women can safely eat. The new sensor is the most mercury-sensitive device ever built and is able to detect very low amounts of the metal, Cho and a team of American and Swiss chemists reported Sept. 9 in the journal Nature Materials.
The new sensor is made of a strip of glass covered in tiny, nanosize gold hairs about 1/100 the width of particle of dust. When researchers dip the strip into a sample of water — or a bit of fish, dissolved in acid — the hairs trap molecules of metals in the sample. Depending on how researchers decide to manufacture the strip, the hairs will capture only molecules of one type of metal. (Researchers are able to make sensors that are sensitive to different metals by adjusting the lengths of the hairs.)
Afterward, researchers use a machine to run an electric current over the strips, determining the amount of metal the golden hairs have trapped.
To check the accuracy of the machine's measurements, the strip's developers compared their measurements of mercury in tap water, lake water and fish from Lake Michigan with the same measurements made by the U.S. Geological Survey using conventional methods. Cho and her colleagues found the two measures were very close.
The new strips should be both easier and cheaper than current metal-testing methods, the scientists say. "With a conventional method, you have to send samples to the laboratory and the analysis equipment costs several million dollars," said Francesco Stellacci, one of the researcher's lead researchers and a materials scientist at the Ecole Polytechnique Fédérale de Lausanne in Switzerland. The strips should cost less than $10 each to manufacture and the measuring machine's price should be a few hundred dollars, he and his colleagues estimated.
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