 |
|
Penn Researchers Take a Big Step Forward in Making Smaller Circuits
August 01, 2005PHILADELPHIA - Physicists at the University of Pennsylvania have overcome a major hurdle in the race to create nanotube-based electronics. In an article in the August issue of the journal Nature Materials, available online now, the researchers describe their method of using nanotubes tiny tubes entirely composed of carbon atoms - to create a functional electronic circuit. Their method creates circuits by dipping semiconductor chips into liquid suspensions of carbon nanotubes, rather than growing the nanotubes directly on the circuit.
"Given their amazing electric properties, nanotubes have been a subject of keen interest for creating such things as chemical sensors, flexible electronics and high-speed, high-device-density microprocessors for computing," said Alan T. Johnson, associate professor in Penn's Department of Physics and Astronomy. "The problem is that the properties we like best about nanotubes their size and physical properties also make them very difficult to manipulate."
Instead of growing nanotubes in a pattern on a silicon chip, as is conventionally done, the Penn researchers devised a means of "sprinkling" nanotubes onto chips.
"We dip the chips into nanotubes much like dipping an ice cream cone into candy," said Danvers Johnston, a graduate student in Johnson's laboratory and lead author of the study. "Ultimately we can make it so that the nanotubes only stick where want them to in order to form a circuit."
Single-walled nanotubes are formed by turning a single sheet of carbon atoms into a seamless cylinder approximately one nanometer a billionth of a meter in diameter.
Nanotubes can be either semiconducting or "metallic" the latter is highly conductive to electricity depending on the exact geometry of the carbon atoms. Semiconducting nanotubes make for exceptional transistors, which is why so much attention has been devoted to finding a way to use them in electronics.
Previously, most nanotube circuits have been made by growing each nanotube on the surface of a chip, using a process known as chemical vapor deposition. Unfortunately, this method often results in a circuit comprised of both types of nanotubes, metallic and semiconducting. Furthermore, the growth direction of the nanotube is arbitrary, and their diameters are large. Small diameter carbon nanotubes are more useful for switches.
"Fortunately, other researchers have made it possible to grow small diameter nanotubes and to separate metallic from semiconducting nanotubes in solution," said Arjun Yodh, a professor in Penn's Department of Physics and Astronomy. "Ultimately our process can create a large batch of small diameter nanotubes in solution, can separate out the semiconducting nanotubes and then can place them in proper position on a patterned silicon chip."
The researchers, along with post-doctoral associate Mohammed F. Islam, found their biggest challenge in purifying the mass-produced nanotubes. The process they used to create nanotubes in bulk frequently adds impurities usually stray bits of carbon and leftover catalysts that ultimately detract from the quality of the nanotubes.
The Penn researchers found a purification scheme for the nanotubes by heating them in moist air with a gentle acid treatment and then using magnetic fields to separate the nanotubes from the impurities. They deposit the nanotubes by dipping a chip covered with a glue-like substance into the nanotube solution, and then they wash off the excess glue and whatever solvents that remain.
The resulting circuits take advantage of unique electrical properties of nanotubes and can be produced in bulk. Since the researchers can create nanotubes via processes separate from the chips, this process allows for a better control of the quality and diameter. The Penn researchers believe there is a definite role for nanotechnology in the future of electronics.
"The only way to make faster processors is to cram more transistors together," Johnson said. "Nanotubes are just about the smallest transistors that exist right now. So the more densely they can be packed on a chip, the faster the chips can become."
Funding for this research was provided by grants from the National Science Foundation and NASA.
University of Pennsylvania
"We dip the chips into nanotubes much like dipping an ice cream cone into candy," said Danvers Johnston, a graduate student in Johnson's laboratory and lead author of the study. "Ultimately we can make it so that the nanotubes only stick where want them to in order to form a circuit."
Single-walled nanotubes are formed by turning a single sheet of carbon atoms into a seamless cylinder approximately one nanometer a billionth of a meter in diameter.
Nanotubes can be either semiconducting or "metallic" the latter is highly conductive to electricity depending on the exact geometry of the carbon atoms. Semiconducting nanotubes make for exceptional transistors, which is why so much attention has been devoted to finding a way to use them in electronics.
Previously, most nanotube circuits have been made by growing each nanotube on the surface of a chip, using a process known as chemical vapor deposition. Unfortunately, this method often results in a circuit comprised of both types of nanotubes, metallic and semiconducting. Furthermore, the growth direction of the nanotube is arbitrary, and their diameters are large. Small diameter carbon nanotubes are more useful for switches.
"Fortunately, other researchers have made it possible to grow small diameter nanotubes and to separate metallic from semiconducting nanotubes in solution," said Arjun Yodh, a professor in Penn's Department of Physics and Astronomy. "Ultimately our process can create a large batch of small diameter nanotubes in solution, can separate out the semiconducting nanotubes and then can place them in proper position on a patterned silicon chip."
The researchers, along with post-doctoral associate Mohammed F. Islam, found their biggest challenge in purifying the mass-produced nanotubes. The process they used to create nanotubes in bulk frequently adds impurities usually stray bits of carbon and leftover catalysts that ultimately detract from the quality of the nanotubes.
The Penn researchers found a purification scheme for the nanotubes by heating them in moist air with a gentle acid treatment and then using magnetic fields to separate the nanotubes from the impurities. They deposit the nanotubes by dipping a chip covered with a glue-like substance into the nanotube solution, and then they wash off the excess glue and whatever solvents that remain.
The resulting circuits take advantage of unique electrical properties of nanotubes and can be produced in bulk. Since the researchers can create nanotubes via processes separate from the chips, this process allows for a better control of the quality and diameter. The Penn researchers believe there is a definite role for nanotechnology in the future of electronics.
"The only way to make faster processors is to cram more transistors together," Johnson said. "Nanotubes are just about the smallest transistors that exist right now. So the more densely they can be packed on a chip, the faster the chips can become."
Funding for this research was provided by grants from the National Science Foundation and NASA.
University of Pennsylvania
Nanotubes Current Events and Nanotubes News RSSNew study confirms exotic electric properties of graphene
First, it was the soccer-ball-shaped molecules dubbed buckyballs. Then it was the cylindrically shaped nanotubes. Now, the hottest new material in physics and nanotechnology is graphene: a remarkably flat molecule made of carbon atoms arranged in hexagonal rings much like molecular chicken wire.
Caltech scientists develop DNA origami nanoscale breadboards for carbon nanotube circuits
In work that someday may lead to the development of novel types of nanoscale electronic devices, an interdisciplinary team of researchers at the California Institute of Technology (Caltech) has combined DNA's talent for self-assembly with the remarkable electronic properties of carbon nanotubes, thereby suggesting a solution to the long-standing problem of organizing carbon nanotubes into nanoscale electronic circuits.
Breakthrough in industrial-scale nanotube processing
Rice University scientists today unveiled a method for the industrial-scale processing of pure carbon-nanotube fibers that could lead to revolutionary advances in materials science, power distribution and nanoelectronics.
Next-generation microcapsules deliver 'chemicals on demand'
Scientists in California are reporting development of a new generation of the microcapsules used in carbon-free copy paper, in which capsules burst and release ink with pressure from a pen.
Transforming Nanowires Into Nano-Tools Using Cation Exchange Reactions
A team of engineers from the University of Pennsylvania has transformed simple nanowires into reconfigurable materials and circuits, demonstrating a novel, self-assembling method for chemically creating nanoscale structures that are not possible to grow or obtain otherwise.
Study shows how carbon nanotubes can affect lining of the lungs
Carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems.
Advance in 'nano-agriculture': Tiny stuff has huge effect on plant growth
With potential adverse health and environmental effects often in the news about nanotechnology, scientists in Arkansas are reporting that carbon nanotubes (CNTs) could have beneficial effects in agriculture.
A step toward better brain implants using conducting polymer nanotubes
Brain implants that can more clearly record signals from surrounding neurons in rats have been created at the University of Michigan. The findings could eventually lead to more effective treatment of neurological disorders such as Parkinson's disease and paralysis.
A recipe for controlling carbon nanotubes
Nanoscopic tubes made of a lattice of carbon just a single atom deep hold promise for delivering medicines directly to a tumor, sensors so keen they detect the arrival or departure of a single electron, a replacement for costly platinum in fuel cells or as energy‐saving transistors and wires.
Friction force differences could offer a new means for sorting and assembling nanotubes
Nanotubes and nanowires are promising building blocks for future integrated nanoelectronic and photonic circuits, nanosensors, interconnects and electro-mechanical nanodevices. But some fundamental issues remain to be resolved - among them, how to position and manipulate the tiny tubes.
More Nanotubes Current Events and Nanotubes News Articles
 |
Carbon Nanotube Science: Synthesis, Properties and Applications by Peter J. F. Harris (Author) Carbon nanotubes represent one of the most exciting research areas in modern science. These molecular-scale carbon tubes are the stiffest and strongest fibres known, with remarkable electronic properties, and potential applications in a wide range of fields. Carbon Nanotube Science is the most concise, accessible book for the field, presenting the basic knowledge that graduates and researchers need to know. Based on the successful Carbon Nanotubes and Related Structures, this new book focuses solely on carbon nanotubes, covering the major advances made in recent years in this rapidly developing field. Chapters focus on electronic properties, chemical and bimolecular functionalisation, nanotube composites and nanotube-based probes and sensors. The book begins with a comprehensive... |
 |
Physical Properties of Carbon Nanotubes by R. Saito (Author) This text is intended for researchers who want to perform theoretical analysis of carbon nanotubes. It can be used by graduate students in a solid state physics to learn how to investigate the structure of carbon nanotubes, its electronic and vibrational properties. |
 |
Nanotube Particular (Primary Contributor) |
 |
Easton MonkeyLite SL CNT Carbon Fiber MTB Riser Bicycle Handlebar (31.8mm Diameter, 635mm Wide, 20mm Rise) by Easton New carbon unidirectional design |
 |
Carbon Nanotubes: Properties and Applications by Michael J. O'Connell (Editor) Since their discovery more than a decade ago, carbon nanotubes (CNTs) have held scientists and engineers in captive fascination, seated on the verge of enormous breakthroughs in areas such as medicine, electronics, and materials science, to name but a few. Taking a broad look at CNTs and the tools used to study them, Carbon Nanotubes: Properties and Applications comprises the efforts of leading nanotube researchers led by Michael O’Connell, protégé of the late father of nanotechnology, Richard Smalley. Each chapter is a self-contained treatise on various aspects of CNT synthesis, characterization, modification, and applications. The book opens with a general introduction to the basic characteristics and the history of CNTs, followed by discussions on synthesis methods and the... |
 |
Carbon Nanotubes: Basic Concepts and Physical Properties by Stephanie Reich (Author), Christian Thomsen (Author), Janina Maultzsch (Author) Carbon nanotubes are exceptionally interesting from a fundamental research point of view. Many concepts of one-dimensional physics have been verified experimentally such as electron and phonon confinement or the one-dimensional singularities in the density of states; other 1D signatures are still under debate, such as Luttinger-liquid behavior. Carbon nanotubes are chemically stable, mechanically very strong, and conduct electricity. For this reason, they open up new perspectives for various applications, such as nano-transistors in circuits, field-emission displays, artificial muscles, or added reinforcements in alloys. This text is an introduction to the physical concepts needed for investigating carbon nanotubes and other one-dimensional solid-state systems. Written for... |
 |
Easton MonkeyLite XC CNT Carbon Fiber MTB Riser Bicycle Handlebar (660mm Wide, 20mm Rise) by Easton Low and high rise (8° sweep | 4° upsweep) |
 |
Carbon Nanotubes: Advanced Topics in the Synthesis, Structure, Properties and Applications (Topics in Applied Physics) by Ado Jorio (Author), Ado Jorio (Editor), Gene Dresselhaus (Editor), Mildred S. Dresselhaus (Editor) The carbon nanotubes field has evolved substantially since the publication of the bestseller Carbon Nanotubes: Synthesis, Structure, Properties and Applications . The present volume builds on the generic aspects of the aforementioned book, which emphasizes the fundamentals, with the new volume emphasizing areas that have grown rapidly since the first volume, guiding future directions where research is needed and highlighting applications. The volume also includes an emphasis on areas like graphene, other carbon-like and other tube-like materials because these fields are likely to affect and influence developments in nanotubes in the next 5 years. |
 |
Carbon Filaments and Nanotubes: Common Origins, Differing Applications? (NATO Science Series E: Applied Sciences, Volume 372) by L.P. Biró (Editor), Carlos A. Bernardo (Editor), G.G. Tibbetts (Editor), Ph. Lambin (Editor) Carbon filament, vapor grown carbon fibers and carbon nanotubes have been discovered to have remarkable properties, opening they way for their use in intriguing and novel applications in electronics, chemistry and materials science. There are many similarities between nanotubes and filaments, leading many researchers to critically compare the two materials, their production, and potential applications. The two materials are compared and contrasted in depth in the present book, which is a comprehensive review of current research activity, growth mechanisms, physical properties, industrial production, and applications. The structures are discussed using a unified approach, which helps to compare growth mechanisms, contrasting morphological differences, and detailing how novel ... |
|
|
Easton MonkeyLite DH CNT Carbon Fiber MTB Riser Bicycle Handlebar (31.8mm Diameter, 711mm Wide, 40mm Rise) by Easton New carbon unidirectional design |
| © 2009 BrightSurf.com |