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Tiny labs need super gasket
Joseph Ogando, Materials Editor -- Design News, June 4, 2001
Ithaca, NY —Any fluid handling system that can transport nanoliter-sized chemical samples around a lab-on-a-chip relies on its share of advanced technology. It also has to rely on the humble gasket.
Miniature analytical devices, which occupy silicon wafers not much bigger than a postage stamp, ask a lot from their gaskets: These gaskets have to exhibit enough chemical resistance to stand up to the solvents used in biological testing. And they have to provide multiple sealing surfaces in order to prevent any cross-contamination between the fluid wells that pock the surface of the chip and serve as miniscule test tubes.
Engineers at Advion BioSciences, a firm that specializes in lab-on-a-chip technology, recently found a new gasket that fit the bill on both scores. For a microsystem that combines a liquid chromatography and mass spectrometry interface on a single chip, they picked Chemtyte gaskets from Greene, Tweed & Co. (Kulpsville, PA).
Made from Chemraz perfluorelastomer, rather than more common silicone or EPDM, the Chemtyte gaskets got the nod primarily because they promised low extractables when exposed to solvents, reports Simon Prosser, Advion's director of new product development.
And extractables count, given how just a little of an errant chemical compound can throw off readings in devices that have molecular resolution. "Extractables are a big worry," says Prosser. "A vanishingly small amount of a trace compound can mask what we're trying to look at," he notes.
The Chemtyte gaskets also gave Advion some design freedom. A lab-on-a-chip typically has 96, 354, or 1,053 different wells with an equal number of sealing surfaces. What's more, they can also have additional fluid-handling passages that bring the chemicals "off-chip" and have more complex sealing surfaces than round wells, explains Barry Chadwick, Greene, Tweed's manager for medical applications.
The company can support a variety of custom gasket geometries thanks to a proprietary compression molding and finishing process. The gaskets, which can be applied not just to silicon but also to glass or ceramic substrates, can be supplied at thicknesses down to 0.002 inches. "Ten-thousandths is the standard thickness," Chadwick adds.
Greene, Tweed can also make the gaskets from less expensive elastomers—like silicone or EPDM. But 0.010-inch-thick gaskets require small amounts of material, so Chadwick thinks most applications will use the pricier material. "Perfluorelastomer is the Rolls Royce of elastomers," he says, "but in this application it doesn't have to cost more than the alternatives."
For more information about gaskets from Greene, Tweed & Co.: Enter 538
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