'Electronic Nose' Could Detect Hazards

Source:

http://www.sciencedaily.com/releases/2007/11/071109171606.htm

ScienceDaily (Nov. 12, 2007) — A tiny "electronic nose" that MIT researchers have engineered with a novel inkjet printing method could be used to detect hazards including carbon monoxide, harmful industrial solvents and explosives.

Led by MIT professor Harry Tuller, the researchers have devised a way to print thin sensor films onto a microchip, a process that could eventually allow for mass production of highly sensitive gas detectors.
"Mass production would be an enormous breakthrough for this kind of gas sensing technology," said Tuller, a professor in the Department of Materials Science and Engineering (MSE), who is presenting the research Oct. 30 at the Composites at Lake Louise Conference in Alberta, Canada.
The prototype sensor, created by Tuller, postdoctoral fellow Kathy Sahner and graduate student Woo Chul Jung, members of MIT's Electroceramics Group in MSE, consists of thin layers of hollow spheres made of the ceramic material barium carbonate, which can detect a range of gases. Using a specialized inkjet print head, tiny droplets of barium carbonate or other gas-sensitive materials can be rapidly deposited onto a surface, in any pattern the researchers design.
The miniature, low-cost detector could be used in a variety of settings, from an industrial workplace to an air-conditioning system to a car's exhaust system, according to Tuller. "There are many reasons why it's important to monitor our chemical environment," he said.
For a sensor to be useful, it must be able to distinguish between gases. For example, a sensor at an airport would need to know the difference between a toxic chemical and perfume, Tuller said. To achieve this, sensors should have an array of films that each respond differently to different gases. This is similar to the way the human sense of smell works, Tuller explained.
"The way we distinguish between coffee's and fish's odor is not that we have one sensor designed to detect coffee and one designed to detect fish, but our nose contains arrays of sensors sensitive to various chemicals. Over time, we train ourselves to know that a certain distribution of vapors corresponds to coffee," he said.
In previous work designed to detect nitrogen oxide (NOx) emissions from diesel exhaust, the researchers created sensors consisting of flat, thin layers of barium carbonate deposited on quartz chips. However, the films were not sensitive enough, and the team decided they needed more porous films with a larger surface area.
To create more texture, they applied the barium carbonate to a layer of microspheres, hollow balls less than a micrometer in diameter made of a plastic polymer. When the microspheres are burned away, a textured, highly porous layer of gas-sensitive film is left behind.
The resulting film, tens of nanometers (billionths of a meter) thick, is much more sensitive than flat films because it allows the gas to readily permeate through the film and interact with a much larger active surface area.
At first, the researchers used a pipette to deposit the barium carbonate and microspheres. However, this process proved time-consuming and difficult to control.
To improve production efficiency, the researchers took advantage of a programmable Hewlett-Packard inkjet print head located in the MIT Laboratory of Organic Optics and Electronics. The inkjet print head, like that in a regular inkjet printer, can deposit materials very quickly and controllably. The special gas-sensitive "inks" used in this work were optimized for printing by Amy Leung, an MIT sophomore in chemical engineering.
This allows the researchers to rapidly produce many small, identical chips containing geometrically well-defined gas-sensing films with micrometer dimensions. Patterns of different gas-sensitive inks, just as in a color printer, can be easily generated to form arrays with very little ink required per sensor.
In future studies, the team hopes to create large arrays of gas-sensitive films with controlled three-dimensional shapes and morphologies.
The research is funded by the National Science Foundation.
Adapted from materials provided by Massachusetts Institute of Technology.

Fausto Intilla

www.oloscience.com

New Technology Can Be Operated By Thought

Source:

http://www.sciencedaily.com/releases/2007/11/071107210708.htm

ScienceDaily (Nov. 9, 2007) — Neuroscientists have significantly advanced brain-machine interface (BMI) technology to the point where severely handicapped people who cannot contract even one leg or arm muscle now can independently compose and send e-mails and operate a TV in their homes. They are using only their thoughts to execute these actions.

Thanks to the rapid pace of research on the BMI, one day these and other individuals may be able to feed themselves with a robotic arm and hand that moves according to their mental commands.
"Our work has shown how important the learning process is when using brain-controlled devices," says Andrew Schwartz, PhD, of the University of Pittsburgh. "By permitting the subject to adaptively recode the generated neural activity, the overall performance of the device is dramatically increased.
"Furthermore, as we have progressed in this work, it has become apparent that the basic idea of 'intention' during learning is very important and can be addressed by the direct observation of the neuronal transformations taking place during this fundamental processing," Schwartz says.
Among the research institutions conducting cutting-edge research on the BMI is the University of Pittsburgh, where scientists recently succeeded in developing the technology that allows a rhesus macaque monkey to mentally control a robotic arm to feed itself pieces of fruit. The robotic arm's fast and smooth movements were triggered by electrical signals that were generated in the monkey's brain when the animal thought about an action.
In previous studies, this lab developed the technology to tap a macaque monkey's motor cortical neural activity making it possible for the animal to use its thoughts to control a robotic arm to reach for food targets presented in 3D space.
In the Pittsburgh lab's latest studies, macaque monkeys not only mentally guided a robotic arm to pieces of food but also opened and closed the robotic arm's hand, or gripper, to retrieve them. Just by thinking about picking up and bringing the fruit to its mouth, the animal fed itself.
The monkey's own arm and hand did not move while it manipulated the two-finger gripper at the end of the robotic arm. The animal used its own sight for feedback about the accuracy of the robotic arm's actions as it mentally moved the gripper to within one-half centimeter of a piece of fruit.
"The monkey developed a great deal of skill using this physical device," says Meel Velliste, PhD. "We are in the process of extending this type of control to a more sophisticated wrist and hand for the performance of dexterous tasks."
Velliste and the other members of the Pittsburgh research team point out that imparting skill and dexterity to these devices will help amputees and paralyzed patients to perform everyday tasks.
The animal's thoughts emitted electrical signals that were recorded by tiny electrodes that the scientists had implanted in the monkey's motor cortex. A computer-decoding algorithm translated the signals into the robotic arm and gripper's movements.
In another study, a Washington University School of Medicine research team has generated new information about a long-held theory about the separate functions and responsibilities of the left brain and the right brain. In the process, the researchers, led by Eric Leuthardt, PhD, and his graduate students Kimberly Wisneski and Nick Anderson, have applied their findings to a new neuroprosthetic strategy to improve the rehabilitation of stroke and trauma victims who have suffered damage to either the right or left half of the brain.
"Classic understanding of brain function has asserted that one hemisphere, or one side of the brain, controls arm and leg movement on the opposite side of the body," Wisneski explains.
The team's new findings indicated that if the left hemisphere were damaged, the right side of the brain still had electrical signals that could be used to trigger right-sided arm and leg movement.
The scientists recorded the brain activity of six epilepsy patients in which electrodes were placed over the surface of their brain for reasons that were not connected to the purpose of the study. (The intracranial electrode arrays were implanted on the surface of each patient's brain to locate the brain areas that were involved with the patient's seizures.) "This access provided us with insights that could not be obtained using other methods," Leuthardt says.
The team recorded electrocorticographic signals while each patient opened and closed his or her hands. These recordings revealed brain activity in the hemisphere on the same side of the body in which movement was occurring. These same-side signals occurred at a lower frequency than did the signals emitted in the hemisphere opposite to the moving side of the body.
In addition, these same-side signals were emitted in spatially distinct areas of the brain and earlier in time in comparison to the hemispheric signals recorded for opposite-side hand movement.
"This evidence demonstrates that the brain encodes information regarding planning for movements of the same-sided limb and that this information is encoded in a way that is unique from that corresponding to opposite-side limb movements," Wisneski says.
The team next determined how these results could be used to improve the rehabilitation of stroke and brain injury patients. Their focus: the brain computer interface (BCI), an external device that was designed to benefit patients with spinal cord injury and other disorders that did not affect the brain. The BCI enables individuals to control with their thoughts alone a cursor on a computer screen, a wheelchair, or a robotic arm.
To benefit stroke and brain injury patients, the BCI would have to be adapted to respond to signals from only one side of the brain.
"To allow these patients to benefit from the use of a brain-computer interface, signals for control for two sides of the body must be acquired from the single functioning hemisphere alone," Leuthardt says. "In this paradigm, one side of the body -- the side opposite to the unaffected half of the brain -- would be controlled through normal physiologic pathways, and the other side of the body -- the side affected by the stroke and on the same side as the unaffected hemisphere -- would be controlled through neuroprosthetic assistance using same-side signals from the undamaged hemisphere."
Other scientists are studying the phenomenon in which neurons are active in the brain's motor cortex, not only when an individual bends a leg but also when he or she observes other people while moving their legs. This neural mechanism may help explain the development of innate skills such as speech and new motor skills such as a golf swing.
Graduate student Dennis Tkach and colleagues at University of Chicago hope to tap this neural mechanism to modify BMI systems for use by people who are paralyzed from spinal cord injury or related trauma. Currently the BMI's functioning depends on mathematical maps that connect brain cell activity to the action -- arm or leg movement, for example -- that the system is designed to replace.
Tkach says that the phenomenon of congruent neural activity may provide the mathematical maps of these paralyzed patients. "The existence of these neurons offers the means of creating this mapping by relating neural activity of the patient to an action observed by that patient," he says. "The neural activity is congruent because the way that the neurons fire during observation of familiar action is the same as the way they fire when the individual is performing that same action."
The University of Chicago study, which was conducted with rhesus monkeys, was the first to analyze a neural system that showed congruent activity with movement on a single cell level in the primary motor cortex.
The monkeys were trained to perform a video task in a two-dimensional, horizontal workspace located in front of them. They guided a circular cursor to a square target. Both the cursor and the target were projected onto the workspace. The animals controlled the cursor by moving an exoskeletal robot arm in which their active arm rested.
They were then trained to relax and watch a playback of the task they had just performed. During the playback, the monkeys saw either or both the target and the cursor on the screen.
"We varied visibility of the video task components in an attempt to gain a better understanding of what facilitates the neural congruency between observation and action," Tkach says. "The study showed that the presence of the goal of an action bears a greater impact on the strength of this congruence, while the observation of the motion to this goal carries minimal importance."
This result emphasized the importance of the goal as the facilitator of this action-like neural response, Tkach says.
The brain cell activity patterns were recorded from arrays of 100 electrodes surgically implanted in the monkeys' motor cortical areas. Because of these arrays, Tkach was able to obtain simultaneous neural activity data from a population of single cells along with a more global neural signal. Analyzing the data, he noted that the activity patterns of the neurons during the observation period correlated highly with the cells' activity patterns when the animal was using its right arm to guide the cursor.
"Our results lead us to believe that when presented with the observation of a familiar action the monkeys inadvertently generate a motor command that is very similar to one that would occur if the animal were to execute the behavior," Tkach says. The congruence of this motor command to the "actual" one was not an all-or-nothing phenomenon but instead spanned a continuum that was contingent upon the components of the observed action that was present.
In other work, Wadsworth Center scientists in Albany, N.Y., have succeeded in developing a BCI that provided people who are severely disabled with the ability to use their personal computers. For example, they were able to word-process, send e-mail messages, and remotely turn on or off the lights or TV in their homes. In the future, even more environmental control options will be available, says Eric Sellers, PhD.
The Wadsworth Center BCI system enabled a scientist with advanced amyotrophic lateral sclerosis (ALS), to communicate by e-mail with his research team. "It has allowed him to continue to direct a highly successful NIH-funded medical research program," Sellers says. "The initial results indicate that the BCI can function without close technical oversight and can improve communication ability and quality of life. This initial success suggests that a home BCI system can be of practical value for people with severe motor disabilities and that caregivers without special expertise can learn to support it."
Five severely disabled people have participated in the Wadsworth research program that evaluates the center's BCI system. The first participant, the 49-year-old scientist with ALS, has been unable to move any muscles in his body except for his eyes. For up to five to seven hours every day since February 2006, he has worn a simple electrode cap on his scalp that picks up the electrical activity generated by his brain. The cap recorded electroencephalographic (EEG, or brain wave) activity at eight scalp locations.
The user's brain waves were translated into simulated keystrokes. Software developed at Wadsworth presented rows and columns of a 72-element, 8" x 9" matrix that flashed in random order while the user paid attention to the element that he or she wanted to select. The software recognized that element and executed the appropriate keystroke. With this design, the patient could use the entire keyboard.
Sellers says that caregivers and family members learned to place the electrode cap on patients' scalps, enable the software, and generally maintain the system, which the researchers monitored remotely via data transferred weekly from patients' homes to the lab. To date, a total of five people with ALS have used the Wadsworth system in their homes.
In addition, the Wadsworth Center team has tested protocols in the laboratory that extend BCI functionality to benefit people with limited eye mobility, poor visual acuity, or difficulty maintaining gaze, impairments that can occur with severe motor disorders such as ALS, brainstem stroke, or cerebral palsy. For these individuals, the scientists have been developing a BCI system that uses auditory rather than visual stimuli.
In the auditory BCI system, the rows and columns of a 6" x 6" matrix of 36 letters and numbers are represented by six environmental sounds. For each selection, the user paid attention to the sound representing the column or row containing the desired choice. Thus far, most of the people who tested this auditory system in the lab used it with accuracy sufficient to support effective BCI operation.
The researchers also have been developing a BCI system that uses sensorimotor rhythms (SMRs), oscillations in the EEG recorded from the scalp over the sensorimotor cortex. The SMRs provided simple communication capabilities, and the people learned to use SMRs to control a computer cursor in one or two dimensions.
Adapted from materials provided by Society for Neuroscience.

Fausto Intilla

www.oloscience.com

New Mini-sensor May Have Biomedical And Security Applications

Source:

http://www.sciencedaily.com/releases/2007/11/071101150116.htm

ScienceDaily (Nov. 6, 2007) — A tiny sensor that can detect magnetic field changes as small as 70 femtoteslas-equivalent to the brain waves of a person daydreaming-has been demonstrated at the National Institute of Standards and Technology (NIST). The sensor could be battery-operated and could reduce the costs of non-invasive biomagnetic measurements such as fetal heart monitoring. The device also may have applications such as homeland security screening for explosives.

Described in the November issue of Nature Photonics,* the prototype device is almost 1000 times more sensitive than NIST's original chip-scale magnetometer demonstrated in 2004 and is based on a different operating principle. Its performance puts it within reach of matching the current gold standard for magnetic sensors, so-called superconducting quantum interference devices or SQUIDs. These devices can sense changes in the 3- to 40-femtotesla range but must be cooled to very low (cryogenic) temperatures, making them much larger, power hungry, and more expensive.
The NIST prototype consists of a single low-power (milliwatt) infrared laser and a rice-grain-sized container with dimensions of 3 by 2 by 1 millimeters. The container holds about 100 billion rubidium atoms in gas form. As the laser beam passes through the atomic vapor, scientists measure the transmitted optical power while varying the strength of a magnetic field applied perpendicular to the beam. The amount of laser light absorbed by the atoms varies predictably with the magnetic field, providing a reference scale for measuring the field. The stronger the magnetic field, the more light is absorbed.
"The small size and high performance of this sensor will open doors to applications that we could previously only dream about," project leader John Kitching says.
The new NIST mini-sensor could reduce the equipment size and costs associated with some non-invasive biomedical tests. (The body's electrical signals that make the heart contract or brain cells fire also simultaneously generate a magnetic field.) The NIST group and collaborators have used a modified version of the original sensor to detect magnetic signals from a mouse heart.**
The new sensor is already powerful enough for fetal heart monitoring; with further work, the sensitivity can likely be improved to a level in the 10 femtotesla range, sufficient for additional applications such as measuring brain activity, the designers say. A femtotesla is one quadrillionth (or a millionth of a billionth) of a tesla, the unit that defines the strength of a magnetic field. For comparison, the Earth's magnetic field is measured in microteslas, and a magnetic resonance imaging (MRI) system operates at several teslas.
To make a complete portable magnetometer, the laser and vapor cell would need to be packaged with miniature optics and a light detector. The vapor cell can be fabricated and assembled on semiconductor wafers using existing techniques for making microelectronics and microelectromechanical systems (MEMS). This design, adapted from a previously developed NIST chip-scale atomic clock, offers the potential for low-cost mass production.
As described in the new paper, NIST scientists demonstrated that the prototype mini-sensor produces a strong signal that changes rapidly with the strength of a magnetic field from the outside world. The device exhibits a consistent minimum level of electromagnetic static, or "white noise," which indicates a stable limit on its overall sensitivity. The authors also estimated that a well-designed compact magnetometer with present sensitivity could operate continuously for weeks on a single AA battery.
Magnetometers need to be designed with applications in mind; smaller vapor cells require less power but are also less sensitive. Thus, an application for which low power is critical would benefit from a very small magnetometer, whereas a larger magnetometer would be more suitable for a different application requiring high sensitivity. The NIST work evaluates the tradeoffs between size, power and performance in a quantifiable way.
"This result suggests that millimeter-scale, low-power, inexpensive, femtotesla magnetometers are feasible ... Such an instrument would greatly expand the range of applications in which atomic magnetometers could be used," the paper states.
The NIST device could be used in a heart monitoring technique known as magnetocardiography (MCG), which is sensitive enough to measure fields of few picoteslas emitted by the fetal heart from small currents in heart muscle cells, providing complementary and perhaps better information than an electrocardiogram. With further improvements, the NIST sensor also might be used in magnetoencephalography (MEG), which measures the magnetic fields produced by electrical activity in the brain, helping to pinpoint tumors or determine function of various parts of the brain. The existing mini-sensor likely will be able to detect some brain activity, such as the signals from alpha waves, which are about 1 picotesla in magnitude at a distance of 1 centimeter from the skull surface, but not the fainter signals from the full range of brain function. (Signals of magnitude 1 picotesla are identifiable with a magnetometer sensitivity of 70 femtotesla per root Hertz.) MCG and MEG offer the advantage of not requiring contrast agents or injected tracers as do other medical procedures such as MRI or positron emission tomography (PET).
Potential NIST collaborators are interested in making a portable MEG helmet that could be worn by epileptics to record brain activity before and during seizures. The devices would be much smaller and lighter than the SQUID helmets currently used for such studies. Kitching said the NIST sensor also may have applications in MRI or in airport screening for explosives based on detection of nuclear quadrupole resonance in nitrogen compounds.
As a non-regulatory agency of the Commerce Department, NIST promotes U.S. innovation and industrial competitiveness by advancing measurement science, standards and technology in ways that enhance economic security and improve our quality of life.
* Vishal Shah, Svenja Knappe, Peter D.D. Schwindt, and John Kitching. Femtotesla Atomic Magnetometry with a Microfabricated Vapor Cell. Nature Photonics. 1 November 2007.
** Brad Lindseth, Peter Schwindt, John Kitching, David Fischer, Vladimir Shusterman. 2007. Non-contact Measurement of Cardiac Electromagnetic Field in Mice Using an Ultra-small Atomic Magnetometer. Feasibility Study. Presented at Computers in Cardiology, Durham, NC, Sept 30-Oct. 3, 2007.
How the NIST Mini-Sensor Works
The NIST compact magnetometer is based on the so-called SERF (spin-exchange relaxation free) principle, which was used by a group at Princeton University in 2003 to enhance the sensitivity of larger, tabletop-sized magnetometers to outperform SQUIDs. The NIST group developed novel approaches and technologies to adapt the SERF concept for tiny and practical devices.
At zero magnetic field, the atoms' electron "spins" (which can be roughly visualized as tiny magnetic arrows pointing through the electrons) all point in the same direction as the laser beam, and the atoms absorb virtually no light. As the magnetic field is increased, the electrons jump to higher-energy levels and their spins go out of sync, causing the atoms to absorb some of the light.
Ordinarily, the atoms would collide randomly and the electron spins would change direction in between collisions, degrading the sensor signal. The SERF approach maintains consistent spins for a relatively long time (10 milliseconds) by combining a low magnetic field with high temperatures of 150 degrees C (302 degrees F). The spins have little time to adjust in between the collisions. Like cars on a highway, the atoms behave more consistently when conditions are crowded.
Adapted from materials provided by National Institute of Standards and Technology.

Fausto Intilla

www.oloscience.com

World's Most Complex Silicon Phased-array Chip Developed

Source:

http://www.sciencedaily.com/releases/2007/10/071030135705.htm

ScienceDaily (Nov. 4, 2007) — UC San Diego electrical engineers have developed the world's most complex “phased array” -- or radio frequency integrated circuit. This DARPA-funded advance is expected to find its way into U.S. defense satellite communication and radar systems. In addition, the innovations in this chip design will likely spill over into commercial applications, such as automotive satellite systems for direct broadcast TV, and new methods for high speed wireless data transfer.

“This is the first 16 element phased array chip that can send at 30-50 GHz. The uniformity and low coupling between the elements, the low current consumption and the small size – it is just 3.2 by 2.6 square millimeters – are all unprecedented. As a whole system, there are many many firsts,” said Gabriel Rebeiz, the electrical engineering professor from the UCSD Jacobs School of Engineering leading the project.
This chip – the UCSD DARPA Smart Q-Band 4x4 Array Transmitter – is strictly a transmitter. “We are working on a chip that can do a transmit and receive function,” said Rebeiz.
“This compact beamforming chip will enable a breakthrough in size, weight, performance and cost in next-generation phased arrays for millimeter-wave military sensor and communication systems,” DARPA officials wrote in a statement.
“DARPA has funded us to try to get everything on a single silicon chip – which would reduce the cost of phased arrays tremendously. In large quantities, this new chip would cost a few dollars to manufacture. Obviously, this is only the transmitter. You still need the receiver but one can easily build the receiver chip based on the designs available in the transmitter chip. Our work addresses the most costly part of the phased array – the 16:1 divider, phase shifters, amplitude controllers and the uniformity and isolation between channels,” said Rebeiz
The chip also contains all the CMOS digital circuits necessary for complete digital control of the phased array, and was done using the commercial Jazz SBC18HX process. This is a first and greatly reduces the fabrication complexity of the phased array. The chip has been designed for use at the defense satellite communications frequency – the Q-band - which goes from 40 to 50 GHz.
“If you take the same design and move it to the 24 or 60 GHz range, you can use it for commercial terrestrial communications,” said Rebeiz who is also a lead on a separate project, funded by Intel and a UC-Discovery Grant, to create silicon CMOS phased array chips that could be embedded into laptops and serve as high speed data transfer tools.
The Intel project is a collaboration between Rebeiz, Larry Larson and Ian Galton – all electrical engineering professors at the UCSD Jacobs School of Engineering. Larson also serves as the chair of the Department of Electrical and Computer Engineering.
“If you wanted to download a large movie file, a base station could find you, zoom onto you, and direct a beam to your receiver chip. This could enable data transfer of hundreds of gigabytes of information very quickly, and without connecting a cable or adhering to the alignment requirements of wireless optical data transfer,” explained Rebeiz who estimated that this kind of system could be available in as little as three years.
Phased Array Background Information
Phased arrays have been around for more than half a century. They are groups of antennas in which the relative phases of the signals that feed them are varied so that the effective radiation pattern of the array is reinforced in a particular direction and suppressed in undesired directions. This property – combined with the fact that radio waves can pass through clouds and most other materials that stymie optical communication systems – has led engineers to use phased arrays for satellite communications, and for detecting incoming airplanes, ships and missiles.
Some phased arrays are larger than highway billboards and the most powerful – used as sophisticated radar, surveillance and communications systems for military aircraft and ships – can cost hundreds of millions of dollars. The high cost has prevented significant spread beyond military and high-end satellite communication applications. Engineers are now working to miniaturize them and fully integrate them into silicon-based electronic systems for both military and commercial applications.
The new UCSD chip packs 16 channels into a 3.2 by 2.6 mm² chip. The input signal is divided on-chip into 16 different paths with equal amplitude and phase using an innovative design, and the phase and gain of each of the 16 channels is controlled electronically to direct the antenna pattern (beam) into a specific direction.
By manipulating the phase, you can steer the beam electronically in nanoseconds. With the amplitude, you control the width of the beam, which is critical, for example, when you send information to from one satellite to another but you don’t want the signal to reach any nearby satellites. And with amplitude and phase control, you can synthesize deep nulls in the antenna pattern so as to greatly reduce the effect of interfering signals from neighboring transmitters.
The work was done by two graduate students, Kwang-Jin Koh and Jason May, both at the Electrical and Computer Engineering Department (ECE) at UCSD. Rebeiz presented the new chip at DARPA TEAM Meeting, August 28-29, 2007 in Chicago, Illinois. Additional details of the chip will be submitted to an academic journal later this year.
Adapted from materials provided by University of California - San Diego.

Fausto Intilla

www.oloscience.com

New Magnet Design Sheds Light On Nanotechnology And Semiconductor Research

Source:

http://www.sciencedaily.com/releases/2007/10/071031152845.htm

ScienceDaily (Oct. 31, 2007) — Engineers at Florida State University's National High Magnetic Field Laboratory have successfully tested a groundbreaking new magnet design that could literally shed new light on nanoscience and semiconductor research.

When the magnet -- called the Split Florida Helix -- is operational in 2010, researchers will have the ability to direct and scatter laser light at a sample not only down the bore, or center, of the magnet, but also from four ports on the sides of the magnet, while still reaching fields above 25 tesla. By comparison, the highest-field split magnet in the world attains 18 tesla. "Tesla" is a measurement of the strength of a magnetic field; 1 tesla is equal to 20,000 times the Earth's magnetic field.
Magnetism is a critical component of a surprising number of modern technologies, including MRIs and disk drives, and high-field magnets stand beside lasers and microscopes as essential research tools for probing the mysteries of nature. With this new magnet, scientists will be able to expand the scope of their experimental approach, learning more about the intrinsic properties of materials by shining light on crystals from angles not previously available in such high magnetic fields. In materials research, scientists look at which kinds of light are absorbed or reflected at different crystal angles, giving them insight into the fundamental electronic structure of matter.
The Split Florida Helix design represents a significant accomplishment for the magnet lab's engineering staff. High magnetic fields exert tremendous forces inside the magnet, and those forces are directed at the small space in the middle . . . that's where Mag Lab engineers cut big holes in it.
"You have enough to worry about with traditional magnets, and then you try to cut huge holes from all four sides from which you can access the magnet," said lab engineer Jack Toth, who is spearheading the project. "Basically, near the midplane, more than half of the magnet structure is cut away for the access ports, and it's still supposed to work and make high magnetic fields."
Magnet engineers worldwide have been trying to solve the problem of creating a magnet with side access at the midsection, but they have met with little success in higher fields. Magnets are created by packing together dense, high-performance copper alloys and running a current through them, so carving out empty space at the heart of a magnet presents a huge engineering challenge.
Instead of fashioning a tiny pinhole to create as little disruption as possible, as other labs have tried, Toth and his team created a design with four big elliptical ports crossing right through the midsection of the magnet. The ports open 50 percent of the total space available for experiments, a capability the laboratory's visiting scientists have long desired.
"It's different from any traditional magnet that we've ever built before, and even the fabrication of our new parts was very challenging," Toth said. "In search of a vendor for manufacturing the prototypes, I had phone conversations where people would promise me, 'Jack, we looked at it from every possible angle and this part is impossible to machine.'"
Of course, that wasn't the case, and the model coil, crafted from a mix of copper-beryllium blocks and copper-silver plates, met expectations during its testing in a field higher than 32 tesla with no damage to its parts.
Though the National Science Foundation-funded model has reached an important milestone, years of work will go into the final product. The lab hopes to have a working magnet for its User Program by 2010, and other research facilities have expressed great interest in having split magnets that can generate high magnetic fields.
Adapted from materials provided by Florida State University.

Fausto Intilla

www.oloscience.com

First Fully-functional Radio From A Single Carbon Nanotube Created

Source:

http://www.sciencedaily.com/releases/2007/10/071031135307.htm

ScienceDaily (Oct. 31, 2007) — Make way for the real nanopod and make room in the Guinness World Records. A team of researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley have created the first fully functional radio from a single carbon nanotube, which makes it by several orders of magnitude the smallest radio ever made.
Wielding a single carbon nanotube 10,000 times smaller than a human hair, this is definitely the smallest radio yet. The nanotube vibrates at radio frequencies to receive the signal, then acts as both amplifier and demodulator. With only a battery and sensitive earphones, it can pick up AM or FM. With such a small receiver or transmitter, you could put a tracking collar on a bacterium.
“A single carbon nanotube molecule serves simultaneously as all essential components of a radio — antenna, tunable band-pass filter, amplifier, and demodulator,” said physicist Alex Zettl, who led the invention of the nanotube radio. “Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation (FM and AM), we were able to demonstrate successful music and voice reception.”
Given that the nanotube radio essentially assembles itself and can be easily tuned to a desired frequency band after fabrication, Zettl believes that nanoradios will be relatively easy to mass-produce. Potential applications, in addition to incredibly tiny radio receivers, include a new generation of wireless communication devices and monitors. Nanotube radio technology could prove especially valuable for biological and medical applications.
“The entire radio would easily fit inside a living cell, and this small size allows it to safely interact with biological systems,” Zettl said. “One can envision interfaces with brain or muscle functions, or radio-controlled devices moving through the bloodstream.”
It is also possible that the nanotube radio could be implanted in the inner ear as an entirely new and discrete way of transmitting information, or as a radically new method of correcting impaired hearing.
Zettl holds joint appointments with Berkeley Lab's Materials Sciences Division (MSD) and the UC Berkeley Physics Department where he is the director of the Center of Integrated Nanomechanical Systems. In recent years, he and his research group have created an astonishing array of devices out of carbon nanotubes - hollow tubular macromolecules only a few nanometers (billionths of a meter) in diameter and typically less than a micron in length – including sensors, diodes and even a motor. The nanotube radio, however, is the first that – literally – rocks!
“When I was a young kid, I got a transistor radio as a gift and it was the greatest thing I could imagine - music coming from a box I could hold in my hand!” Zettl said. “When we first played our nanoradio, I was just as excited as I was when I first turned on that transistor radio as a kid.”
The carbon nanotube radio consists of an individual carbon nanotube mounted to an electrode in close proximity to a counter-electrode, with a DC voltage source, such as from a battery or a solar cell array, connected to the electrodes for power. The applied DC bias creates a negative electrical charge on the tip of the nanotube, sensitizing it to oscillating electric fields. Both the electrodes and nanotube are contained in vacuum, in a geometrical configuration similar to that of a conventional vacuum tube.
Kenneth Jensen, a graduate student in Zettl’s research group, did the actual design and construction of the radio.
“We started out by making an exceptionally sensitive force sensor,” Jensen said.“Nanotubes are like tiny cat whiskers.Small forces, on the order of attonewtons, cause them to deflect a significant amount.By detecting this deflection, you can infer what force was acting on the nanotube. This incredible sensitivity becomes even greater at the nanotube’s flexural resonance frequency, which falls within the frequencies of radio broadcasts, cell phones and GPS broadcasting. Because of this high resonance frequency, Alex (Zettl) suggested that nanotubes could be used to make a radio.”
Although it has the same essential components, the nanotube radio does not work like a conventional radio. Rather than the entirely electrical operation of a conventional radio, the nanotube radio is in part a mechanical operation, with the nanotube itself serving as both antenna and tuner.
Incoming radio waves interact with the nanotube’s electrically charged tip, causing the nanotube to vibrate. These vibrations are only significant when the frequency of the incoming wave coincides with the nanotube’s flexural resonance frequency, which, like a conventional radio, can be tuned during operation to receive only a pre-selected segment, or channel, of the electromagnetic spectrum.
Amplification and demodulation properties arise from the needle-point geometry of carbon nanotubes, which gives them unique field emission properties. By concentrating the electric field of the DC bias voltage applied across the electrodes, the nanotube radio produces a field-emission current that is sensitive to the nanotube’s mechanical vibrations. Since the field-emission current is generated by the external power source, amplification of the radio signal is possible. Furthermore, since field emission is a non-linear process, it also acts to demodulate an AM or FM radio signal, just like the diode used in traditional radios.
“What we see then is that all four essential components of a radio receiver are compactly and efficiently implemented within the vibrating and field-emitting carbon nanotube,” said Zettl. “This is a totally different approach to making a radio - the exploitation of electro-mechanical movement for multiple functions. In other words, our nanotube radio is a true NEMS (nano-electro-mechanical system) device.”
Because carbon nanotubes are so much smaller than the wavelengths of visible light, they cannot be viewed with even the highest powered optical microscope. Therefore, to observe the critical mechanical motionof their nanotube radio, Zettl and his research team, which in addition to Jensen, also included post-doc Jeff Weldon and graduate student Henry Garcia, mounted their nanotube radio inside a high resolution transmission electron microscope (TEM). A sine-wave carrier radio signal was launched from a nearby transmitting antenna and when the frequencies of the transmitted carrier wave matched the nanotube resonance frequency, radio reception became possible.
“To correlate the mechanical motions of the nanotube to an actual radio receiver operation, we launched an FM radio transmission of the song Good Vibrations by the Beach Boys,” said Zettl. “After being received, filtered, amplified, and demodulated all by the nanotube radio, the emerging signal was further amplified by a current preamplifier, sent to an audio loudspeaker and recorded. The nanotube radio faithfully reproduced the audio signal, and the song was easily recognizable by ear.”
When the researchers deliberately detuned the nanotube radio from the carrier frequency, mechanical vibrations faded and radio reception was lost. A “lock” on a given radio transmission channel could be maintained for many minutes at a time, and it was not necessary to operate the nanotube radio inside a TEM. Using a slightly different configuration, the researchers successfully transmitted and received signals across a distance of several meters.
“The integration of all the electronic components of a radio happened naturally in the nanotube itself,” said Jensen. “Within a few hours of figuring out that our force sensor was in fact a radio, we were playing music!”
Added Zettl, “Our nanotube radio is sophisticated and elegant in the physics of its operation, but sheer simplicity in technical design. Everything about it works perfectly, without additional patches or tricks.”
Berkeley Lab’s Technology Transfer Department is now seeking industrial partners to further develop and commercialize this technology.
A paper on this work is now on-line at the Nano Letters Website. It will also be published in the November 2007 print edition of Nano Letters. The paper is entitled “Nanotube Radio” and the co-authors are Zettl, Jensen, Weldon and Garcia. In that same print edition, there appears a paper by Peter Burke and Chris Rutherglen of UC Irvine, reporting on the use of a carbon nanotube as a demodulator.
The nanotube radio research was supported by the U.S. Department of Energy and by the National Science Foundation within the Center of Integrated Nanomechanical Systems.
Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.
Adapted from materials provided by DOE/Lawrence Berkeley National Laboratory.

Fausto Intilla
www.oloscience.com

You Thought Your Nano Was Small: Nano-sized Detector Turns Radio Waves Into Music

Source:

http://www.sciencedaily.com/releases/2007/10/071017131851.htm

ScienceDaily (Oct. 19, 2007) — Researchers in California report development of the world's first working radio system that receives radio waves wirelessly and converts them to sound signals through a nano-sized detector made of carbon nanotubes.
The "carbon nanotube radio" device is thousands of times smaller than the diameter of a human hair. The development marks an important step in the evolution of nano-electronics and could lead to the production of the world's smallest radio, the scientists say.
Peter Burke and Chris Rutherglen developed a carbon nanotube "demodulator" that is capable of translating AM radio waves into sound. In a laboratory demonstration, the researchers incorporated the detector into a complete radio system and used it to successfully transmit classical music wirelessly from an iPod to a speaker several feet away from the music player.
Although other researchers have developed nano-sized radio wave detectors in the past, the current study marks the first time that a nano-sized detector has been demonstrated in an actual working radio system, the scientists say. The study demonstrates the feasibility of making other radio components at the nanoscale in the future and may eventually lead to a "truly integrated nanoscale wireless communications system," they say. Such a device could have numerous industrial, commercial, medical and other applications.
Their findings appeared online October 17 and are scheduled for publication in the Nov. 14 print edition of ACS' Nano Letters.
Adapted from materials provided by American Chemical Society.

Fausto Intilla
www.oloscience.com