Getting out of a sticky situation

June 1, 2006
Researchers at the National Institute of Standards and Technology (NIST) and George Mason University (GMU) have found an easy way to bond thermoplastic

Researchers at the National Institute of Standards and Technology (NIST) and George Mason University (GMU) have found an easy way to bond thermoplastic microchannel plates together with solvent. This technology could be used for low-cost, high-volume production of disposable “lab-on-a-chip” devices.

Microfluidics could perform rapid and inexpensive chemical and biochemical analyses using tiny channels less than a fraction of a millimeter wide to move samples and reagents through the device. For high-volume production, the channels likely will be molded or embossed in high-quality thermoplastic and then sealed with a cover plate. However, bonding the two pieces together securely without blocking or altering the channels may pose a problem.

One approach is to weld the two plates together by clamping them and heating the plastic until the polymer chains begin diffusing together. This requires just the right combination of time, pressure, and temperature — which must be fine-tuned for each new lot of plastic. The other method is to weld the pieces with a solvent-type glue.

A team from NIST and GMU suggests clamping the two plates together, injecting a tiny amount of solvent at one end of the network of channels, and applying a vacuum at the other end. As the solvent is quickly sucked through the channels without clogging, a minute amount is drawn between the plates by capillary action and welds them together. The whole process takes about 8 minutes. To demonstrate utility, the team used this technique to successfully perform high-efficiency electrophoretic separation of 400-base single-strand DNA ladders — a typical microfluidics application — in the devices fabricated.

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