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'Nanocantilevers' yield surprises critical for designing new detectors
August 29, 2006Researchers at Purdue University have made a discovery about the behavior of tiny structures called nanocantilevers that could be crucial in designing a new class of ultra-small sensors for detecting viruses, bacteria and other pathogens.
The nanocantilevers, which resemble tiny diving boards made of silicon, could be used in future detectors because they vibrate at different frequencies when contaminants stick to them, revealing the presence of dangerous substances. Because of the nanocantilever's minute size, it is more sensitive than larger devices, promising the development of advanced sensors that detect minute quantities of a contaminant to provide an early warning that a dangerous pathogen is present.
The researchers were surprised to learn that the cantilevers, coated with antibodies to detect certain viruses, attract different densities - or quantity of antibodies per area - depending on the size of the cantilever. The devices are immersed into a liquid containing the antibodies to allow the proteins to stick to the cantilever surface.
"But instead of simply attracting more antibodies because they are longer, the longer cantilevers also contained a greater density of antibodies, which was very unexpected," said Rashid Bashir, a researcher at the Birck Nanotechnology Center and a professor of electrical and computer engineering and biomedical engineering at Purdue University. The research also shows that the density is greater toward the free end of the cantilevers.
The engineers found that the cantilevers vibrate faster after the antibody attachment if the devices have about the same nanometer-range thickness as the protein layer. Moreover, the longer the protein-coated nanocantilever, the faster the vibration, which could only be explained if the density of antibodies were to increase with increasing lengths, Bashir said. The research group also proved this hypothesis using optical measurements and then worked with Ashraf Alam, a researcher at the Birck Nanotechnology Center and professor of electrical and computer engineering, to develop a mathematical model that describes the behavior.
The information will be essential to properly design future "nanomechanical" sensors that use cantilevers, Bashir said.
Findings are detailed in a research paper appearing online today (Monday, Aug. 28) in Proceedings of the National Academy of Sciences. The paper was authored by Amit K. Gupta, a former Purdue doctoral student working with Bashir and now a postdoctoral researcher at Harvard University; Pradeep R. Nair, a doctoral student in electrical and computer engineering; Demir Akin, research assistant professor of biomedical engineering; Michael Ladisch, Distinguished Professor of Agricultural and Biological Engineering with a joint appointment in the Weldon School of Biomedical Engineering; Steven Broyles, a professor of biochemistry; Alam and Bashir.
The work, funded by the National Institutes of Health, is aimed at developing advanced sensors capable of detecting minute quantities of viruses, bacteria and other contaminants in air and fluids by coating the cantilevers with proteins, including antibodies that attract the contaminants. Such sensors will have applications in areas including environmental-health monitoring in hospitals and homeland security. So-called "lab-on-a-chip" technologies could make it possible to replace bulky lab equipment with miniature sensors, saving time, energy and materials. Thousands of the cantilevers can be fabricated on a 1-square-centimeter chip, Bashir said.
The cantilevers studied in the recent work range in length from a few microns to tens of microns, or millionths of a meter, and are about 20 nanometers thick, which is also roughly the thickness of the antibody coating. A nanometer is a billionth of a meter, or approximately the length of 10 hydrogen atoms strung together.
A cantilever naturally "resonates," or vibrates at a specific frequency, depending on its mass and mechanical properties. The mass changes when contaminants land on the devices, causing them to vibrate at a different "resonant frequency, " which can be quickly detected. Because certain proteins attract only specific contaminants, the change in vibration frequency means a particular contaminant is present.
Ordinarily, when using cantilevers that are on a thickness scale of microns or larger, attaching mass causes the resonant frequency to decrease, which is the opposite of what occurs with the nanoscale-thickness cantilevers. Researchers believe the unexpected behavior is a result of the antibodies being about the same thickness as the ultra-thin nanocantilevers, meaning their vibration is more profoundly affected than a more massive cantilever would be by the attachment of the antibodies.
"The conclusion is that when the attached mass is as thick as the cantilever, then you not only affect the mass but you also affect a key property called the net stiffness constant and the resonant frequency can actually go up," Bashir said.
Gupta measured the cantilever's vibration frequency using an instrument called a laser Doppler vibrometer, which detects changes in the cantilever's velocity as it vibrates. The researchers then treated the antibodies with a fluorescent dye and took images of the proteins on the cantilever's surface, proving that the density increases with longer cantilevers.
Nair and Alam then developed a mathematical model to explain why the density increases as the area of the cantilever rises. The model uses a "diffusion reaction equation" to simulate the antibodies sticking to the cantilever's surface.
The research is based at the Birck Nanotechnology Center at Discovery Park, the university's hub for interdisciplinary research.
Purdue University
"But instead of simply attracting more antibodies because they are longer, the longer cantilevers also contained a greater density of antibodies, which was very unexpected," said Rashid Bashir, a researcher at the Birck Nanotechnology Center and a professor of electrical and computer engineering and biomedical engineering at Purdue University. The research also shows that the density is greater toward the free end of the cantilevers.
The engineers found that the cantilevers vibrate faster after the antibody attachment if the devices have about the same nanometer-range thickness as the protein layer. Moreover, the longer the protein-coated nanocantilever, the faster the vibration, which could only be explained if the density of antibodies were to increase with increasing lengths, Bashir said. The research group also proved this hypothesis using optical measurements and then worked with Ashraf Alam, a researcher at the Birck Nanotechnology Center and professor of electrical and computer engineering, to develop a mathematical model that describes the behavior.
The information will be essential to properly design future "nanomechanical" sensors that use cantilevers, Bashir said.
Findings are detailed in a research paper appearing online today (Monday, Aug. 28) in Proceedings of the National Academy of Sciences. The paper was authored by Amit K. Gupta, a former Purdue doctoral student working with Bashir and now a postdoctoral researcher at Harvard University; Pradeep R. Nair, a doctoral student in electrical and computer engineering; Demir Akin, research assistant professor of biomedical engineering; Michael Ladisch, Distinguished Professor of Agricultural and Biological Engineering with a joint appointment in the Weldon School of Biomedical Engineering; Steven Broyles, a professor of biochemistry; Alam and Bashir.
The work, funded by the National Institutes of Health, is aimed at developing advanced sensors capable of detecting minute quantities of viruses, bacteria and other contaminants in air and fluids by coating the cantilevers with proteins, including antibodies that attract the contaminants. Such sensors will have applications in areas including environmental-health monitoring in hospitals and homeland security. So-called "lab-on-a-chip" technologies could make it possible to replace bulky lab equipment with miniature sensors, saving time, energy and materials. Thousands of the cantilevers can be fabricated on a 1-square-centimeter chip, Bashir said.
The cantilevers studied in the recent work range in length from a few microns to tens of microns, or millionths of a meter, and are about 20 nanometers thick, which is also roughly the thickness of the antibody coating. A nanometer is a billionth of a meter, or approximately the length of 10 hydrogen atoms strung together.
A cantilever naturally "resonates," or vibrates at a specific frequency, depending on its mass and mechanical properties. The mass changes when contaminants land on the devices, causing them to vibrate at a different "resonant frequency, " which can be quickly detected. Because certain proteins attract only specific contaminants, the change in vibration frequency means a particular contaminant is present.
Ordinarily, when using cantilevers that are on a thickness scale of microns or larger, attaching mass causes the resonant frequency to decrease, which is the opposite of what occurs with the nanoscale-thickness cantilevers. Researchers believe the unexpected behavior is a result of the antibodies being about the same thickness as the ultra-thin nanocantilevers, meaning their vibration is more profoundly affected than a more massive cantilever would be by the attachment of the antibodies.
"The conclusion is that when the attached mass is as thick as the cantilever, then you not only affect the mass but you also affect a key property called the net stiffness constant and the resonant frequency can actually go up," Bashir said.
Gupta measured the cantilever's vibration frequency using an instrument called a laser Doppler vibrometer, which detects changes in the cantilever's velocity as it vibrates. The researchers then treated the antibodies with a fluorescent dye and took images of the proteins on the cantilever's surface, proving that the density increases with longer cantilevers.
Nair and Alam then developed a mathematical model to explain why the density increases as the area of the cantilever rises. The model uses a "diffusion reaction equation" to simulate the antibodies sticking to the cantilever's surface.
The research is based at the Birck Nanotechnology Center at Discovery Park, the university's hub for interdisciplinary research.
Purdue University
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Cantilevers Current Events and Cantilevers News RSSBioengineers develop a microfabricated device to measure cellular forces during tissue development
A University of Pennsylvania-collaboration of bioengineers studying the physical forces generated by individual cells has created a tiny micron-sized device that allows researchers to measure and manipulate cellular forces as assemblies of living cells reorganize themselves into tissues.
Caltech scientists create nanoscale zipper cavity that responds to single photons of light
Physicists at the California Institute of Technology (Caltech) have developed a nanoscale device that can be used for force detection, optical communication, and more.
Catching the lightwave: Nano-mechanical sensors 'wired' by photonics
As researchers push towards detection of single molecules, single electron spins and the smallest amounts of mass and movement, Yale researchers have demonstrated silicon-based nanocantilevers, smaller than the wavelength of light, that operate on photonic principles eliminating the need for electric transducers and expensive laser setups.
New method for detecting explosives
A group of researchers in Tennessee and Denmark has discovered a way to sensitively detect explosives based on the physical properties of their vapors. Their technology, which is currently being developed into prototype devices for field testing, is described in the latest issue of the journal Review of Scientific Instruments, which is published by the American Institute of Physics (AIP).
New research identifies faster detection of viruses
A more specific and faster detection of viruses has been identified in new research by Trinity College Dublin's Professor of Physics, Martin Hegner at Trinity College's Centre of Research on Adaptive Nanostructures and Nanodevices (CRANN) and an international team of researchers.
Clemson researchers advance nano-scale electromechanical sensors
Clemson physics professor Apparao Rao and his team are researching nano-scale cantilevers that have the potential to read and alert us to toxic chemicals or gases in the air. Put them into a small handheld device and the potential is there for real-time chemical alerts in battle, in industry, in health care and even at home.
Nanotechnology boosts war on superbugs
This week Nature Nanotechnology journal (October 12th) reveals how scientists from the London Centre for Nanotechnology (LCN) at UCL are using a novel nanomechanical approach to investigate the workings of vancomycin, one of the few antibiotics that can be used to combat increasingly resistant infections such as MRSA.
Fast AFM probes measure multiple properties of biomolecules or materials simultaneously
New research demonstrates that novel probe technology based on flexible membranes can replace conventional atomic force microscopy (AFM) cantilevers for applications such as fast topographic imaging, quantitative material characterization and single molecule mechanics measurements.
'Radio wave cooling' offers new twist on laser cooling
Visible and ultraviolet laser light has been used for years to cool trapped atoms-and more recently larger objects-by reducing the extent of their thermal motion.
Bioengineers at University of Pennsylvania devise nanoscale system to measure cellular forces
University of Pennsylvania researchers have designed a nanoscale system to observe and measure how individual cells react to external forces.
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Coolaroo 10 Foot Round Cantilever Freestanding Patio Umbrella, Smoke by Gale Pacific, USA Large 10' Smoke Cantilever freestanding Patio Umbrella with unique Coolaroo knitted fabric provides up to 90% UV Block , reduces temperature underneath by up to 32%, is easy to clean and mildew resistant. Includes premium crank mechanism and 3 position tilt-aluminum pole. 5 year UV warranty. |
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Cantilever-Based CMOS Sensor Systems by D. Lange (Author), O. Brand (Author), H. Baltes (Author) This book introduces the use of industrial CMOS processes to produce arrays of nanomechanical cantilever transducers with on-chip driving and signal conditioning circuitry. These cantilevers are familiar from Scanning Probe Microscopy (SPM) and allow the sensitive detection of physical quantities such as forces and mass changes. The book is divided into three parts. First fabrication aspects and the mechanisms of cantilever resonators are introduced. Of the possible driving and sensing mechanisms, electrothermal and magnetic excitation, as well as piezoresistive detection and the use of MOS transistors for the deflection detection are introduced. This is followed by two application examples: The use of resonant cantilevers for the mass-sensitive detection of volatile organic compounds,... |
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Cantilever-Based CMOS Sensor Systems by Springer This book introduces the use of industrial CMOS processes to produce arrays of nanomechanical cantilever transducers with on-chip driving and signal conditioning circuitry. These cantilevers are familiar from Scanning Probe Microscopy (SPM) and allow the sensitive detection of physical quantities such as forces and mass changes. The book is divided into three parts. First fabrication aspects and the mechanisms of cantilever resonators are introduced. Of the possible driving and sensing mechanisms, electrothermal and magnetic excitation, as well as piezoresistive detection and the use of MOS transistors for the deflection detection are introduced. This is followed by two application examples: The use of resonant cantilevers for the mass-sensitive detection of volatile organic compounds,... |
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Avid Shorty 6 Bicycle Cantilever Brake (Silver, Rear) by SRAM Powerful and innovative short-arm brakes that use side-pull technology and convenience in a road-lever, compatible design - perfect for cyclo-cross, tandem, recumbent and sticker-laden courier bikes. Tough linear springs for stiff, positive response. High straddle cable clearance to accommodate mud and/or fenders. Cross Road cartridge pads are a full 70mm in length for greater stopping power. Forged aluminum construction with Mercury Silver finish. Specify Front or Rear. |
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10 ft Round Cantilever Aluminium by Coolaroo by Coolaroo Cantilever design with aluminum frame.Breathable umbrella moderates temperatures Synthetic fabric resists mold and mildew * Carton Dimension - 90.5"x22.5"x6".Weight - 48.5 lbs * 5-year warranty on UV degradation on Fabric * For wood decking:Use wood bolts to bolt into wood through the holes in the legs * For grass:Use tent stakes in holes of feet to stake in yard * For concrete, etc.:Purchase "paver stones" at local hardware/garden store to place between feet.We suggest 18" pavers/flagstones that come to the edge of the feet; useno smaller than 12" pavers/flagstones. There is a lip on the feet andthe pavers lay on that and weigh down the umbrella. |
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Jeff Murphy - Cantilever Jeff Murphy (Performer) The first solo effort from SHOES' Jeff Murphy. This 11-song collection was self-produced and engineered at home, in the spirit of the first McCartney album, Emitt Rhodes early works and Todd Rundgren's "Something/Anything" | |
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13" To 24" Single Arm LCD Cantilever Mount by OmniMount Cantilever arm allows extension and 180 degree lateral rotation for viewing from multiple locaton. Allows tilt and swivel of flat panel for optimum viewing angle. Provides optimum viewing angles Portrait or landscape positioning Low profile design - folds flat against wall Integrated cable management Lift & Lock mounting for easy installation Die cast aluminum construction 40 pounds (18.1 kg) max weight capacity |
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Beta C20L Five-Section Cantilever Long Series Tool Box by Beta The Ciceri family began producing tools in Northern Italy in the 1880s. Today, family owned Beta, or Beta Utensili is known for its direct involvement in Grand Prix racing, a relationship that dates back to the early 1970s. |
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Boss Caressoft Cantilever Sled Base Guest Chair by Boss Beautifully upholstered with ultra soft and durable caressoft upholstery. Executive mid back styling with extra lumbar support. Padded armrests covered with caressoft upholstery. Matching guest chair for models (B7401) and (B7406). | |
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Coolaroo 10 Foot Round Cantilever Freestanding Patio Umbrella, Mocha by Gale Pacific, USA The cantilever designs are timeless, distinctive and thanks to Coolaroo's unique long life 90% UV block outdoor fabric covers they are also guaranteed to retain their striking good looks season after season. Coolaroo's "breathable" fabric is much cooler underneath than other fabrics, making for a more pleasurable dining experience. The 10 foot umbrella has a crank lift and the unique Coolaroo knitted fabric provides up to 90% UV block and allows the cover to 'breathe' reducing temperatures underneath by up to 32%. The fabric resists mold and mildew and is easy to clean. The smooth action crank mechanism provides easy operation and solid construction provides years of outdoor use. Fabric has a five year warranty against UV degradation. |
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