| Posted: February 12, 2010 |
Novel sensor exploits traditional weakness of nano-devices |
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(Nanowerk News) By taking advantage of a phenomenon that until now has been a virtual showstopper for electronics designers, a team led by Oak Ridge National Laboratory's Panos Datskos is developing a chemical and biological sensor with unprecedented sensitivity.
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Ultimately, researchers believe this new "sniffer" will achieve a detection level that approaches the theoretical limit, surpassing other state-of-the-art chemical sensors. The implications could be significant for anyone whose job is to detect explosives, biological agents and narcotics.
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"While the research community has been avoiding the nonlinearity associated with the nanoscale mechanical oscillators, we are embracing it," said co-developer Nickolay Lavrik, a member of the Department of Energy lab's Center for Nanophase Materials Sciences Division. "In the end, we hope to have a device capable of detecting incredibly small amounts of explosives compared to today's chemical sensors."
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The device consists of a digital camera, a laser, imaging optics, a signal generator, digital signal processing and other components that collectively, much like a dog's nose, can detect tiny amounts of substances in the air.
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The underlying concept is based on micro-scale resonators that are similar to microcantilevers used in atomic force microscopy, which has recently been explored as mass and force sensing devices. Although the basic principle is simple - measuring changes in the resonance frequency due to mass changes - a number of obstacles have impeded widespread applications of such systems.
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"These challenges are due to requirements of measuring and analyzing tiny oscillation amplitudes that are about the size of a hydrogen atom," Lavrik said. Such traditional approaches require sophisticated low-noise electronic components such as lock-in amplifiers and phase-locked loops, which add cost and complexity.
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Instead, this new type of sniffer works by deliberately hitting the microcantilevers with relatively large amounts of energy associated with a range of frequencies, forcing them into wide oscillation, or movement. Lavrik likened the response to a diving board's movement after a swimmer dives.
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"In the past, people wanted to avoid this high amplitude because of the high distortion associated with that type of response," said Datskos, a member of the Measurement Science and Systems Engineering Division. "But now we can exploit that response by tuning the system to a very specific frequency that is associated with the specific chemical or compound we want to detect."
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When the target chemical reacts with the microcantilever, it shifts the frequency depending on the weight of the compound, thereby providing the detection.
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"With this new approach, when the microcantilever stops oscillating we know with high certainty that the target chemical or compound is present," Lavrik said.
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The researchers envision this technology being incorporated in a handheld instrument that could be used by transportation security screeners, law enforcement officials and the military. Other potential applications are in biomedicine, environmental science, homeland security and analytical chemistry.
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With adequate levels of funding, Datskos envisions a prototype being developed within six to 18 months.
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