A tiny scale that is sensitive enough to weigh a single virus particle may become the basis for biodefense detection systems that can instantly recognize dangerous viruses. Scientists recently fabricated a microscopic, silicon-based device that looks like a tiny diving board and vibrates naturally at a particular frequency. Researchers measure the frequency by bouncing laser light off the tip of the device, known as a cantilever. Because the cantilever is so small, about one micron wide, or approximately one-hundredth the width of a human hair, it is extremely sensitive to changes in mass, even the addition of a single virus.
The researchers succeeded in placing a lone particle of the vaccinia virus on the cantilever, allowing them to weigh the virus. The addition of the virus changed the vibration frequency in a measurable way, signaling a change in weight. The virus weighed in at nine femtograms, or quadrillionths of a gram. The next step in development will involve efforts to coat the cantilevers with antibodies that will allow only a single type of virus to stick to the device. This research represents a significant step toward the development of handheld systems that can detect viruses, bacteria, and other airborne microbes in real time. Such biosensors could detect bioterror agents that might be used in attacks, and may be useful for other purposes, such as monitoring air quality in hospitals.
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