David Kirkpatrick

August 4, 2010

Invisibility cloak update

It’s been several months since I’ve come across any news on invisibility cloak technology, something of a pet subject around here, but here’s the very latest — findings on transformation optics.

From the second link, the release:

New findings promising for ‘transformation optics,’ cloaking

WEST LAFAYETTE, Ind. — Researchers have overcome a fundamental obstacle in using new “metamaterials” for radical advances in optical technologies, including ultra-powerful microscopes and computers and a possible invisibility cloak.

The metamaterials have been plagued by a major limitation: too much light is “lost,” or absorbed by metals such as silver and gold contained in the metamaterials, making them impractical for optical devices.

However, a Purdue University team has solved this hurdle, culminating three years of research based at the Birck Nanotechnology Center at the university’s Discovery Park.

“This finding is fundamental to the whole field of metamaterials,” said Vladimir M. Shalaev, Purdue’s Robert and Anne Burnett Professor of Electrical and Computer Engineering. “We showed that, in principle, it’s feasible to conquer losses and develop these materials for many applications.”

Research findings are detailed in a paper appearing on Aug. 5 in the journal Nature.

The material developed by Purdue researchers is made of a fishnet-like film containing holes about 100 nanometers in diameter and repeating layers of silver and aluminum oxide. The researchers etched away a portion of the aluminum oxide between silver layers and replaced it with a “gain medium” formed by a colored dye that can amplify light.

Other researchers have applied various gain media to the top of the fishnet film, but that approach does not produce sufficient amplification to overcome losses, Shalaev said.

Instead, the Purdue team found a way to place the dye between the two fishnet layers of silver, where the “local field” of light is far stronger than on the surface of the film, causing the gain medium to work 50 times more efficiently.

The approach was first developed by former Purdue doctoral student Hsiao-Kuan Yuan, now at Intel Corp., and it was further developed and applied by doctoral student Shumin Xiao.

Unlike natural materials, metamaterials are able to reduce the “index of refraction” to less than one or less than zero. Refraction occurs as electromagnetic waves, including light, bend when passing from one material into another. It causes the bent-stick-in-water effect, which occurs when a stick placed in a glass of water appears bent when viewed from the outside.

Being able to create materials with an index of refraction that’s negative or between one and zero promises a range of potential breakthroughs in a new field called transformation optics. Possible applications include a “planar hyperlens” that could make optical microscopes 10 times more powerful and able to see objects as small as DNA; advanced sensors; new types of “light concentrators” for more efficient solar collectors; computers and consumer electronics that use light instead of electronic signals to process information; and a cloak of invisibility.

Excitement about metamaterials has been tempered by the fact that too much light is absorbed by the materials. However, the new approach can dramatically reduce the “absorption coefficient,” or how much light and energy is lost, and might amplify the incident light so that the metamaterial becomes “active,” Shalaev said.

“What’s really important is that the absorption coefficient can be as small as only one-millionth of what it was before using our approach,” Shalaev said. “We can even have amplification of light instead of its absorption. Here, for the first time, we showed that metamaterials can have a negative refractive index and amplify light.”

The Nature paper was written by Xiao, senior research scientist Vladimir P. Drachev, principal research scientist Alexander V. Kildishev, doctoral student Xingjie Ni, postdoctoral fellow Uday K. Chettiar, Yuan, and Shalaev.

Fabricating the material was a major challenge, Shalaev said.

First, the researchers had to learn how to precisely remove as much as possible of the aluminum oxide layer in order to vacate space for dye without causing a collapse of the structure.

“You remove it almost completely but leave a little bit to act as pillars to support the structure, and then you spin coat the dye-doped polymer inside the structure,” he said.

The researchers also had to devise a way to deposit just the right amount of dye mixed with an epoxy between the silver layers of the perforated film.

“You can’t deposit too much dye and epoxy, which have a positive refractive index, but only a thin layer about 50 nanometers thick, or you lose the negative refraction,” Shalaev said.

Future work may involve creating a technology that uses an electrical source instead of a light source, like semiconductor lasers now in use, which would make them more practical for computer and electronics applications.

###

The work was funded by the U.S. Army Research Office and the National Science Foundation.

Hit this link for the related image (it’s just too big for this blog and I didn’t feel like doing any resizing), and here’s the accompanying caption for the image:

This illustration shows the structure of a new device created by Purdue researchers to overcome a fundamental obstacle in using new “metamaterials” for radical advances in optical technologies, including ultrapowerful microscopes and computers and a possible invisibility cloak. The material developed by the researchers is a perforated, fishnet-like film made of repeating layers of silver and aluminum oxide. The researchers etched away a portion of the aluminum oxide between silver layers and replaced it with a “gain medium” to amplify light. (Birck Nanotechnology Center, Purdue University)

July 13, 2010

CEO salaries are too high — here comes the science

I could have filed this one under, “the department of ‘no duh’,” as well. Not sure if this intersection of thermodynamic physics statistics and free market capitalism is completely accurate, but the idea that executive compensation has been completely divorced from the free market for a long time is very obvious to anyone outside the boardroom. If nothing else you can look no further than the many, many examples of CEOs who utterly failed at the job — sometimes from day one in a short tenure — who leave the company worse for the experience and with a golden parachute that would make Midas jealous.

The release:

‘Econophysics’ points way to fair salaries in free market

WEST LAFAYETTE, Ind. – A Purdue University researcher has used “econophysics” to show that under ideal circumstances free markets promote fair salaries for workers and do not support CEO compensation practices common today.

The research presents a new perspective on 18th century economist Adam Smith’s concept that an “invisible hand” drives a free market economy to a collective good.

“It is generally believed that the free market cares only about efficiency and not fairness. However, my theory shows that even though companies focus primarily on making profits and individuals are only looking out for themselves, the collective self-organizing free market dynamics, under ideal conditions, leads to fairness as an emergent property,” said Venkat Venkatasubramanian, a professor of chemical engineering. “In reality, the self-correcting free market mechanisms have broken down for CEOs and other top executives in the market, but they seem to be working fine for the remaining 95 percent of employees.”

Venkatasubramanian is proposing the use of statistical mechanics and econophysics concepts to gain some insights into the problem.

“This is at the intersection of physics and economics,” he said. “We are generalizing concepts from statistical thermodynamics – the branch of physics that describes the behavior of gases, liquids and solids under heat – to analyze how free markets should perform ideally.”

In previous work, Venkatasubramanian used the approach to determine that the 2008 salaries of the top 35 CEOs in the United States were about 129 times their ideal fair salaries – and CEOs in the Standard & Poor’s 500 averaged about 50 times their fair pay – raising questions about the effectiveness of the free market to properly determine CEO pay.

In the new work, the researcher has determined that fairness is integral to a normally functioning free market economy.

Findings are detailed in a research paper that appeared in June in the online journal Entropy and is available at http://www.mdpi.com/1099-4300/12/6/1514/

A key idea in Venkatasubramanian’s theory is a new interpretation of entropy, used in science to measure disorder in thermodynamics and uncertainty in information theory. He shows, however, that entropy also is a measure of fairness, an insight that seems to have been largely missed over the years, he said.

“Venkat’s insight goes beyond the simple grafting of the mathematics of information theory and statistical physics onto the question of fairness of salary distributions within a free market economy,” said Andrew Hirsch, a Purdue physics professor familiar with the research. “He has recast the notion of entropy into a context that has meaning and relevance for this particular problem.”

Venkatasubramanian calls his new theory, “statistical teleodynamics,” from the Greek telos, which means goal-driven.

“In statistical thermodynamics, we study the movement of large numbers of molecules,” Venkatasubramanian said. “In economic systems, we have a large number of people moving around in a free market system, but instead of thermal energy driving the movement people are motivated by goals.”

His theory describes how goal-driven “rational agents,” or people, will behave in a free market economic environment under ideal conditions.

“The bottom line is that the free market does care about fairness,” he said. “Clearly, the next step is to conduct more comprehensive studies of salary distributions in various organizations and sectors in order to understand in greater detail the deviations in the real world from the ideal, fairness maximizing, free market for labor.”

January 28, 2010

The microbots are coming …

Filed under: Science, Technology — Tags: , , , , , — David Kirkpatrick @ 1:53 pm

… and that sounds like a good thing.

Via KurzweilAI.net:

Insectlike ‘microids’ might walk, run, work in colonies
Physorg.com, Jan. 27, 2010

Insectlike “microids” — robots the size of ants that move their tiny legs and mandibles using solid-state “muscles” — have been modeled by Jason Clark, an assistant professor of electrical, computer and mechanical engineering at Purdue University.

The microids could have significantly better dexterity than previous microscale robots, while having the ability to “scavenge vibrational energy” from the environment to recharge their power supply.

He also envisions the possibility of thousands of microids working in unison and communicating with each other to perform a complex task.


(Jason Clark)


Read Original Article>>

November 27, 2009

Semiconducting nanowires are coming

With all the news about nanotechnology and wiring that’s been coming out over the last year or so, this release is no surprise.

The release:

November 26, 2009

Nanowires key to future transistors, electronics

WEST LAFAYETTE, Ind. –

Nanowire formation
Download photo
caption below

A new generation of ultrasmall transistors and more powerful computer chips using tiny structures called semiconducting nanowires are closer to reality after a key discovery by researchers at IBM, Purdue University and the University of California at Los Angeles.The researchers have learned how to create nanowires with layers of different materials that are sharply defined at the atomic level, which is a critical requirement for making efficient transistors out of the structures.

 

“Having sharply defined layers of materials enables you to improve and control the flow of electrons and to switch this flow on and off,” said Eric Stach, an associate professor of materials engineering at Purdue.

Electronic devices are often made of “heterostructures,” meaning they contain sharply defined layers of different semiconducting materials, such as silicon and germanium. Until now, however, researchers have been unable to produce nanowires with sharply defined silicon and germanium layers. Instead, this transition from one layer to the next has been too gradual for the devices to perform optimally as transistors.

The new findings point to a method for creating nanowire transistors.

The findings are detailed in a research paper appearing Friday (Nov. 27) in the journal Science. The paper was written by Purdue postdoctoral researcher Cheng-Yen Wen, Stach, IBM materials scientists Frances Ross, Jerry Tersoff and Mark Reuter at the Thomas J. Watson Research Center in Yorktown Heights, N.Y, and Suneel Kodambaka, an assistant professor at UCLA’s Department of Materials Science and Engineering.

Whereas conventional transistors are made on flat, horizontal pieces of silicon, the silicon nanowires are “grown” vertically. Because of this vertical structure, they have a smaller footprint, which could make it possible to fit more transistors on an integrated circuit, or chip, Stach said.

“But first we need to learn how to manufacture nanowires to exacting standards before industry can start using them to produce transistors,” he said.

Nanowires might enable engineers to solve a problem threatening to derail the electronics industry. New technologies will be needed for industry to maintain Moore’s law, an unofficial rule stating that the number of transistors on a computer chip doubles about every 18 months, resulting in rapid progress in computers and telecommunications. Doubling the number of devices that can fit on a computer chip translates into a similar increase in performance. However, it is becoming increasingly difficult to continue shrinking electronic devices made of conventional silicon-based semiconductors.

“In something like five to, at most, 10 years, silicon transistor dimensions will have been scaled to their limit,” Stach said.

Transistors made of nanowires represent one potential way to continue the tradition of Moore’s law.

The researchers used an instrument called a transmission electron microscope to observe the nanowire formation. Tiny particles of a gold-aluminum alloy were first heated and melted inside a vacuum chamber, and then silicon gas was introduced into the chamber. As the melted gold-aluminum bead absorbed the silicon, it became “supersaturated” with silicon, causing the silicon to precipitate and form wires. Each growing wire was topped with a liquid bead of gold-aluminum so that the structure resembled a mushroom.

Then, the researchers reduced the temperature inside the chamber enough to cause the gold-aluminum cap to solidify, allowing germanium to be deposited onto the silicon precisely and making it possible to create a heterostructure of silicon and germanium.

The cycle could be repeated, switching the gases from germanium to silicon as desired to make specific types of heterostructures, Stach said.

Having a heterostructure makes it possible to create a germanium “gate” in each transistor, which enables devices to switch on and off.

The work is based at IBM’s Thomas J. Watson Research Center and Purdue’s Birck Nanotechnology Center in the university’s Discovery Park and is funded by the National Science Foundation through the NSF’s Electronic and Photonic Materials Program in the Division of Materials Research.

PHOTO CAPTION:
Researchers are closer to using tiny devices called semiconducting nanowires to create a new generation of ultrasmall transistors and more powerful computer chips. The researchers have grown the nanowires with sharply defined layers of silicon and germanium, offering better transistor performance. As depicted in this illustration, tiny particles of a gold-aluminum alloy were alternately heated and cooled inside a vacuum chamber, and then silicon and germanium gases were alternately introduced. As the gold-aluminum bead absorbed the gases, it became “supersaturated” with silicon and germanium, causing them to precipitate and form wires. (Purdue University, Birck Nanotechnology Center/Seyet LLC)

August 16, 2009

Nanolaser could lead to optical computer and more

Sounds promising. The field of alternate computation — such a quantum, optical, biological, et. al. — is always interesting.

The release:

New nanolaser key to future optical computers and technologies

Because the new device, called a “spaser,” is the first of its kind to emit visible light, it represents a critical component for possible future technologies based on “nanophotonic” circuitry, said Vladimir Shalaev, the Robert and Anne Burnett Professor of Electrical and Computer Engineering at Purdue University.

Such circuits will require a laser-light source, but current lasers can’t be made small enough to integrate them into electronic chips. Now researchers have overcome this obstacle, harnessing clouds of electrons called “surface plasmons,” instead of the photons that make up light, to create the tiny spasers.

Findings are detailed in a paper appearing online Sunday (Aug. 16) in the journal Nature, reporting on work conducted by researchers at Purdue, Norfolk State University and Cornell University.

Nanophotonics may usher in a host of radical advances, including powerful “hyperlenses” resulting in sensors and microscopes 10 times more powerful than today’s and able to see objects as small as DNA; computers and consumer electronics that use light instead of electronic signals to process information; and more efficient solar collectors.

“Here, we have demonstrated the feasibility of the most critical component – the nanolaser – essential for nanophotonics to become a practical technology,” Shalaev said.

The “spaser-based nanolasers” created in the research were spheres 44 nanometers, or billionths of a meter, in diameter – more than 1 million could fit inside a red blood cell. The spheres were fabricated at Cornell, with Norfolk State and Purdue performing the optical characterization needed to determine whether the devices behave as lasers.

The findings confirm work by physicists David Bergman at Tel Aviv University and Mark Stockman at Georgia State University, who first proposed the spaser concept in 2003.

“This work represents an important milestone that may prove to be the start of a revolution in nanophotonics, with applications in imaging and sensing at a scale that is much smaller than the wavelength of visible light,” said Timothy D. Sands, the Mary Jo and Robert L. Kirk Director of the Birck Nanotechnology Center in Purdue’s Discovery Park.

The spasers contain a gold core surrounded by a glasslike shell filled with green dye. When a light was shined on the spheres, plasmons generated by the gold core were amplified by the dye. The plasmons were then converted to photons of visible light, which was emitted as a laser.

Spaser stands for surface plasmon amplification by stimulated emission of radiation. To act like lasers, they require a “feedback system” that causes the surface plasmons to oscillate back and forth so that they gain power and can be emitted as light. Conventional lasers are limited in how small they can be made because this feedback component for photons, called an optical resonator, must be at least half the size of the wavelength of laser light.

The researchers, however, have overcome this hurdle by using not photons but surface plasmons, which enabled them to create a resonator 44 nanometers in diameter, or less than one-tenth the size of the 530-nanometer wavelength emitted by the spaser.

“It’s fitting that we have realized a breakthrough in laser technology as we are getting ready to celebrate the 50th anniversary of the invention of the laser,” Shalaev said.

The first working laser was demonstrated in 1960.

The research was conducted by Norfolk State researchers Mikhail A. Noginov, Guohua Zhu and Akeisha M. Belgrave; Purdue researchers Reuben M. Bakker, Shalaev and Evgenii E. Narimanov; and Cornell researchers Samantha Stout, Erik Herz, Teeraporn Suteewong and Ulrich B. Wiesner.

Future work may involve creating a spaser-based nanolaser that uses an electrical source instead of a light source, which would make them more practical for computer and electronics applications.

 

###

The work was funded by the National Science Foundation and U.S. Army Research Office and is affiliated with the Birck Nanotechnology Center, the Center for Materials Research at Norfolk State, and Cornell’s Materials Science and Engineering Department.

IMAGE CAPTION:

Researchers have created the tiniest laser since its invention nearly 50 years ago. Because the new device, called a “spaser,” is the first of its kind to emit visible light, it represents a critical component for possible future technologies based on “nanophotonic” circuitry. The color diagram (a) shows the nanolaser’s design: a gold core surrounded by a glasslike shell filled with green dye. Scanning electron microscope images (b and c) show that the gold core and the thickness of the silica shell were about 14 nanometers and 15 nanometers, respectively. A simulation of the SPASER (d) shows the device emitting visible light with a wavelength of 525 nanometers. (Birck Nanotechnology Center, Purdue University)

A publication-quality image is available at http://news.uns.purdue.edu/images/+2009/shalaev-spasers.jpg

Abstract on the research in this release is available at: http://news.uns.purdue.edu/x/2009b/090817ShalaevSpasers.html

STORY AND PHOTO CAN BE FOUND AT:

http://news.uns.purdue.edu/x/2009b/090817ShalaevSpasers.html

May 22, 2009

The latest in cloaking tech

I’ve done plenty of blogging on invisibility cloaking technology. Here’s a release from yesterday on the very latest news. It does seem we’re getting pretty close to an actual invisibility cloak. Science fiction becomes science fact once again.

The release:

New ‘broadband’ cloaking technology simple to manufacture

IMAGE: This image shows the design of a new type of invisibility cloak that is simpler than previous designs and works for all colors of the visible spectrum, making it possible…

Click here for more information. 

WEST LAFAYETTE, Ind. – Researchers have created a new type of invisibility cloak that is simpler than previous designs and works for all colors of the visible spectrum, making it possible to cloak larger objects than before and possibly leading to practical applications in “transformation optics.”

Whereas previous cloaking designs have used exotic “metamaterials,” which require complex nanofabrication, the new design is a far simpler device based on a “tapered optical waveguide,” said Vladimir Shalaev, Purdue University’s Robert and Anne Burnett Professor of Electrical and Computer Engineering.

Waveguides represent established technology – including fiber optics – used in communications and other commercial applications.

The research team used their specially tapered waveguide to cloak an area 100 times larger than the wavelengths of light shined by a laser into the device, an unprecedented achievement. Previous experiments with metamaterials have been limited to cloaking regions only a few times larger than the wavelengths of visible light.

Because the new method enabled the researchers to dramatically increase the cloaked area, the technology offers hope of cloaking larger objects, Shalaev said.

Findings are detailed in a research paper appearing May 29 in the journal Physical Review Letters. The paper was written by Igor I. Smolyaninov, a principal electronic engineer at BAE Systems in Washington, D.C.; Vera N. Smolyaninova, an assistant professor of physics at Towson University in Maryland; Alexander Kildishev, a principal research scientist at Purdue’s Birck Nanotechnology Center; and Shalaev.

“All previous attempts at optical cloaking have involved very complicated nanofabrication of metamaterials containing many elements, which makes it very difficult to cloak large objects,” Shalaev said. “Here, we showed that if a waveguide is tapered properly it acts like a sophisticated nanostructured material.”

The waveguide is inherently broadband, meaning it could be used to cloak the full range of the visible light spectrum. Unlike metamaterials, which contain many light-absorbing metal components, only a small portion of the new design contains metal.

Theoretical work for the design was led by Purdue, with BAE Systems leading work to fabricate the device, which is formed by two gold-coated surfaces, one a curved lens and the other a flat sheet. The researchers cloaked an object about 50 microns in diameter, or roughly the width of a human hair, in the center of the waveguide.

“Instead of being reflected as normally would happen, the light flows around the object and shows up on the other side, like water flowing around a stone,” Shalaev said.

The research falls within a new field called transformation optics, which may usher in a host of radical advances, including cloaking; powerful “hyperlenses” resulting in microscopes 10 times more powerful than today’s and able to see objects as small as DNA; computers and consumer electronics that use light instead of electronic signals to process information; advanced sensors; and more efficient solar collectors.

Unlike natural materials, metamaterials are able to reduce the “index of refraction” to less than one or less than zero. Refraction occurs as electromagnetic waves, including light, bend when passing from one material into another. It causes the bent-stick-in-water effect, which occurs when a stick placed in a glass of water appears bent when viewed from the outside. Each material has its own refraction index, which describes how much light will bend in that particular material and defines how much the speed of light slows down while passing through a material.

Natural materials typically have refractive indices greater than one. Metamaterials, however, can be designed to make the index of refraction vary from zero to one, which is needed for cloaking.

The precisely tapered shape of the new waveguide alters the refractive index in the same way as metamaterials, gradually increasing the index from zero to 1 along the curved surface of the lens, Shalaev said.

Previous cloaking devices have been able to cloak only a single frequency of light, meaning many nested devices would be needed to render an object invisible.

Kildishev reasoned that the same nesting effect might be mimicked with the waveguide design. Subsequent experiments and theoretical modeling proved the concept correct.

Researchers do not know of any fundamental limit to the size of objects that could be cloaked, but additional work will be needed to further develop the technique.

Recent cloaking findings reported by researchers at other institutions have concentrated on a technique that camouflages features against a background. This work, which uses metamaterials, is akin to rendering bumps on a carpet invisible by allowing them to blend in with the carpet, whereas the Purdue-based work concentrates on enabling light to flow around an object.

 

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Related Web site:

Vladimir Shalaev:
https://engineering.purdue.edu/ECE/People/profile?resource_id=3322

IMAGE CAPTION:

This image shows the design of a new type of invisibility cloak that is simpler than previous designs and works for all colors of the visible spectrum, making it possible to cloak larger objects than before and possibly leading to practical applications in “transformation optics.” (Purdue University)

A publication-quality image is available at http://news.uns.purdue.edu/images/+2009/shalaev-cloaking.jpg

Abstract on the research in this release is available at: http://news.uns.purdue.edu/x/2009a/090520ShalaevCloaking.html

January 22, 2009

Gel rocket fuel

Okay, this has now become a release dump but I couldn’t resist this story. It’s just that cool

The release:

January 21, 2009

Researchers cooking up new gelled rocket fuels

WEST LAFAYETTE, Ind. –

Testing gelled
rocket fuels
Download photo

caption below

Engineers and food scientists are teaming up to develop a new type of gelled fuel the consistency of orange marmalade designed to improve the safety, performance and range of rockets for space and military applications.

“This is a very multidisciplinary project,” said Stephen Heister, the Purdue University professor of aeronautics and astronautics who is leading one of two teams on the project, which is funded by the U.S. Army Research Office.

 

Gels are inherently safer than liquids because they don’t leak, and they also would allow the military to better control rockets than is possible with solid fuels now used. Motors running on gelled fuels could be throttled up and down and controlled more precisely than conventional rockets that use solid propellants, Heister said.

“You can turn the engine on and off, you can coast, go fast or slow,” he said. “You have much greater control, which means more range for missiles. The gelled propellants also tend to have a little more energy than the solid propellants.”

Gelled fuels also could be used in thrusters to position satellites and on NASA space missions.

The team includes researchers from mechanical engineering, aeronautics and astronautics, food science, and agricultural and biological engineering at Purdue, as well as researchers from Iowa State University and University of Massachusetts.

Paul Sojka, a professor of mechanical engineering and an associate director of the project, is building an experiment to take high-speed videos of the gelatinous fuel’s behavior. Jets of the gel form during the fuel-injection process.

“These jets are wiggling, there are pulsations, and those pulsations, we believe, lead to the formation of specific spray patterns and droplet formation,” Sojka said. “The fluid mechanics of gels are quite challenging. The viscous properties of the gel change depending on how fast it’s flowing, which is not true of common liquids such as water or gasoline.”

The project will tap the expertise of food scientists and food engineers, who are accustomed to working with gels, said Carlos Corvalan, an associate professor of food science.

“Gels are more complex than ordinary solids and fluids,” Corvalan said. “Fluids are characterized by viscosity, and solids are characterized by elasticity. Because gels share properties of both solids and fluids, they possess viscoelastic properties, or a combination of both.”

Food science and agricultural engineering researchers will study these viscoelastic properties and create simulations describing how the gels behave.

The five-year, $6.4 million “spray and combustion of gelled hypergolic propellants” project is a U.S. Army Multidisciplinary University Research Initiative, or MURI. Another team is led by Pennsylvania State University.

Future rockets could require that gelled propellants be sprayed by fuel injectors into a motor’s combustion chamber at rates of thousands of pounds per second. Using the gelled propellants, however, will require a thorough knowledge of how the fuel breaks into droplets as it is being sprayed into the chamber.

The fuels are hypergolic, meaning they require no ignition source but ignite spontaneously when mixed with an oxidizer. The fuel and oxidizer tanks each feed into a separate fuel injector. As the streams of fuel and oxidizer mix, they form droplets that ignite.

“There is an unsteadiness of these two jets, and these fluctuations can have all sorts of ramifications in terms of engine performance,” said Sojka, who specializes in research to learn what happens between the fuel and oxidizer streams as they form elliptical sheets, spaghetti-like strands and droplets.

The high-speed movies are recorded at about 10,000 frames per second, or roughly 300 times faster than the typical video signal.

The collision of fuel and oxidizer jets causes “impact waves.”

“We are trying to understand the source of those waves and be able to control or capitalize on the unsteadiness to make smooth combustion,” Heister said.

Purdue faculty members and graduate students are conducting experiments at the university’s Maurice J. Zucrow Laboratories, in the Department of Food Science and in the School of Agricultural and Biological Engineering aimed at developing a comprehensive spray model that describes the precise behavior of propellant droplets in a rocket motor.

One aim is to be able to consistently create the relatively small, uniform droplets that would be needed for rocket propulsion. Food scientists are familiar with processes used to create droplets in foods.

“The texture of those foods is closely associated with the average size and range of sizes of droplets,” said Osvaldo Campanella, a professor of agricultural and biological engineering. “In a combustion chamber you also want to control droplet size, but for a different reason – to precisely control combustion. You want uniform combustion, and for that you need controlled drop size.”

Corvalan will lead work to develop simulations that determine the viscoelastic behavior of the gels and droplets.

Researchers will first work with water-based gels that simulate fuels and will eventually conduct experiments using actual propellants.

“It’s kind of like orange marmalade without the rind,” Heister said. “We are going to make this gel and push it through holes and study how it flows and how big the drops are. Eventually we’ll study the real gelled fuels, which can be quite hazardous and reactive, so we will use them in small quantities and under tightly controlled conditions.”

The viscoelastic properties of the gels will not only be experimentally measured, but molecular models representing the gels also will be developed as part of research in Purdue’s Department of Chemistry. The models will enable researchers to predict the behavior of gels and optimize their formulations.

Information from experiments and modeling will be used to design systems that have improved combustion.

Timothee Pourpoint, a research assistant professor of aeronautics and astronautics, is in charge of setting up and maintaining a propulsion lab to test the fuels at Zucrow. Because the fuels being tested are toxic, the lab will be equipped with a specialized ventilation system. Pourpoint conducted extensive research on hypergolic fuels for his doctoral thesis at Purdue.

 

PHOTO CAPTION:
Timothee Pourpoint, a research assistant professor of aeronautics and astronautics, is in charge of designing and operating a new Purdue lab to test gelled rocket fuels that have the consistency of orange marmalade. The fuels are designed to improve the safety, performance and range of rockets for space and military applications, and the research will involve a team of engineers and food scientists. Standing in the new lab are, from left, Tim Phillips and Mark James, both graduate students in aeronautics and astronautics, Pourpoint and Travis Kubal, a graduate student in mechanical engineering. (Purdue News Service photo/Andrew Hancock)

October 17, 2008

Transformation optics promise big payoff

It’s been quite a while since I’ve blogged on the possibility of a “cloak of invisibility,” so this PhysOrg article caught my eye. It covers a research field known as transformation optics, and the promise there is great. We’re talking the aforementioned cloak, plusultra-powerful microscopes and computers. All this is done by harnessing nanotechnology and “metamaterials.”

From the second link:

The field, which applies mathematical principles similar to those in Einstein’s theory of general relativity, will be described in an article to be published Friday (Oct. 17) in the journal Science. The article will appear in the magazine’s Perspectives section and was written by Vladimir Shalaev, Purdue’s Robert and Anne Burnett Professor of Electrical and Computer Engineering.

The list of possible breakthroughs includes a cloak of invisibility; computers and consumer electronics that use light instead of electronic signals to process information; a “planar hyperlens” that could make optical microscopes 10 times more powerful and able to see objects as small as DNA; advanced sensors; and more efficient solar collectors.

“Transformation optics is a new way of manipulating and controlling light at all distances, from the macro- to the nanoscale, and it represents a new paradigm for the science of light,” Shalaev said. “Although there were early works that helped to develop the basis for transformation optics, the field was only recently established thanks in part to papers by Sir John Pendry at the Imperial College, London, and Ulf Leonhardt at the University of St. Andrews in Scotland and their co-workers.”

July 21, 2008

Cheap LEDs

Filed under: et.al. — Tags: , , — David Kirkpatrick @ 1:48 pm

This is music to my ears. From KurzweilAI.net:

Low-cost LED lights?
KurzweilAI.net, July 21, 2008

Purdue University researchers have developed a new fabrication process that promises to make LEDs cost-competitive with compact fluorescent lights, which are four times more efficient than conventional incandescent lights, but contain harmful mercury.

They replaced the expensive sapphire-based substrate with low-cost, metal-coated silicon wafers using a built-in reflective layer of zirconium nitride, while solving its chemical instability problems.

Another advantage of silicon is that it dissipates heat better than sapphire, reducing damage caused by heating, which is likely to improve reliability and increase the lifetime of LED lighting.

LEDs also are expected to be far longer lasting than conventional lighting, lasting perhaps as long as 15 years before burning out.

Incandescent bulbs are about 10 percent efficient; white LEDs range from 47 percent to 64 percent efficient, but LED lights on the market cost about $100.

The researchers expect affordable LED lights to be on the market within two years.

Purdue University news release

 

I’ve become something of an efficient lighting geek. This news is great!

Here’s the release linked above:

July 17, 2008

Advance brings low-cost, bright LED lighting closer to reality

WEST LAFAYETTE, Ind. –

Operating a “reactor”
Download photo

caption below

Researchers at Purdue University have overcome a major obstacle in reducing the cost of “solid state lighting,” a technology that could cut electricity consumption by 10 percent if widely adopted.

The technology, called light-emitting diodes, or LEDs, is about four times more efficient than conventional incandescent lights and more environmentally friendly than compact fluorescent bulbs. The LEDs also are expected to be far longer lasting than conventional lighting, lasting perhaps as long as 15 years before burning out.

 

“The LED technology has the potential of replacing all incandescent and compact fluorescent bulbs, which would have dramatic energy and environmental ramifications,” said Timothy D. Sands, the Basil S. Turner Professor of Materials Engineering and Electrical and Computer Engineering.

The LED lights are about as efficient as compact fluorescent lights, which contain harmful mercury.

But LED lights now on the market are prohibitively expensive, in part because they are created on a substrate, or first layer, of sapphire. The Purdue researchers have solved this problem by developing a technique to create LEDs on low-cost, metal-coated silicon wafers, said Mark H. Oliver, a graduate student in materials engineering who is working with Sands.

Findings are detailed in a research paper appearing this month in the journal Applied Physics Letters, published by the American Institute of Physics.

LEDs designed to emit white light are central to solid-state lighting, semiconducting devices made of layers of materials that emit light when electricity is applied. Conventional lighting generates light with hot metal filaments or glowing gasses inside glass tubes.

The LEDs have historically been limited primarily to applications such as indicator lamps in electronics and toys, but recent advances have made them as bright as incandescent bulbs.

The light-emitting ingredient in LEDs is a material called gallium nitride, which is used in the sapphire-based blue and green LEDs, including those in traffic signals. The material also is used in lasers in high-definition DVD players.

The sapphire-based technology, however, is currently too expensive for widespread domestic-lighting use, costing at least 20 times more than conventional incandescent and compact fluorescent light bulbs.

One reason for the high cost is that the sapphire-based LEDs require a separate mirrorlike collector to reflect light that ordinarily would be lost.

In the new silicon-based LED research, the Purdue engineers “metallized” the silicon substrate with a built-in reflective layer of zirconium nitride.

“When the LED emits light, some of it goes down and some goes up, and we want the light that goes down to bounce back up so we don’t lose it,” said Sands, the Mary Jo and Robert L. Kirk Director of the Birck Nanotechnology Center in Purdue’s Discovery Park.

Ordinarily, zirconium nitride is unstable in the presence of silicon, meaning it undergoes a chemical reaction that changes its properties.

The Purdue researchers solved this problem by placing an insulating layer of aluminum nitride between the silicon substrate and the zirconium nitride.

“One of the main achievements in this work was placing a barrier on the silicon substrate to keep the zirconium nitride from reacting,” Sands said.

Until the advance, engineers had been unable to produce an efficient LED created directly on a silicon substrate with a metallic reflective layer.

The Purdue team used a technique common in the electronics industry called reactive sputter deposition. Using the method, the researchers bombarded the metals zirconium and aluminum with positively charged ions of argon gas in a vacuum chamber. The argon ions caused metal atoms to be ejected, and a reaction with nitrogen in the chamber resulted in the deposition of aluminum nitride and zirconium nitride onto the silicon surface. The gallium nitride was then deposited by another common technique known as organometallic vapor phase epitaxy, performed in a chamber, called a reactor, at temperatures of about 1,000 degrees Celsius, or 1,800 degrees Fahrenheit.

As the zirconium nitride, aluminum nitride and gallium nitride are deposited on the silicon, they arrange themselves in a crystalline structure matching that of silicon.

“We call this epitaxial growth, or the ordered arrangement of atoms on top of the substrate,” Sands said. “The atoms travel to the substrate, and they move around on the silicon until they find the right spot.”

This crystalline formation is critical to enabling the LEDs to perform properly.

“It all starts with silicon, which is a single crystal, and you end up with gallium nitride that’s oriented with respect to the silicon through these intermediate layers of zirconium nitride and aluminum nitride,” Sands said. “If you just deposited gallium nitride on a glass slide, for example, you wouldn’t get the ordered crystalline structure and the LED would not operate efficiently.”

Using silicon will enable industry to “scale up” the process, or manufacture many devices on large wafers of silicon, which is not possible using sapphire. Producing many devices on a single wafer reduces the cost, Sands said.

Another advantage of silicon is that it dissipates heat better than sapphire, reducing damage caused by heating, which is likely to improve reliability and increase the lifetime of LED lighting, Oliver said.

The widespread adoption of solid-state lighting could have a dramatic impact on energy consumption and carbon emissions associated with electricity generation since about one-third of all electrical power consumed in the United States is from lighting.

“If you replaced existing lighting with solid-state lighting, following some reasonable estimates for the penetration of that technology based on economics and other factors, it could reduce the amount of energy we consume for lighting by about one-third,” Sands said. “That represents a 10 percent reduction of electricity consumption and a comparable reduction of related carbon emissions.”

Incandescent bulbs are about 10 percent efficient, meaning they convert 10 percent of electricity into light and 90 percent into heat.

“Its actually a better heater than a light emitter,” Sands said.

By comparison, efficiencies ranging from 47 percent to 64 percent have been seen in some white LEDs, but the LED lights now on the market cost about $100.

“When the cost of a white LED lamp comes down to about $5, LEDs will be in widespread use for general illumination,” Sands said. “LEDs are still improving in efficiency, so they will surpass fluorescents. Everything looks favorable for LEDs, except for that initial cost, a problem that is likely to be solved soon.”

He expects affordable LED lights to be on the market within two years.

Two remaining hurdles are to learn how to reduce defects in the devices and prevent the gallium nitride layer from cracking as the silicon wafer cools down after manufacturing.

“The silicon wafer expands and contracts less than the gallium nitride,” Sands said. “When you cool it down, the silicon does not contract as fast as the gallium nitride, and the gallium nitride tends to crack.”

Sands said he expects both challenges to be met by industry.

“These are engineering issues, not major show stoppers,” he said. “The major obstacle was coming up with a substrate based on silicon that also has a reflective surface underneath the epitaxial gallium nitride layer, and we have now solved this problem.”

The research, based at the Birck Nanotechnology Center and funded by the U.S. Department of Energy through its solid-state lighting program, is part of a larger project at Purdue aimed at perfecting white LEDs for lighting.

The Applied Physics Letters paper was written by researchers in the School of Materials Engineering and the School of Electrical and Computer Engineering: Oliver; fellow graduate students Jeremy L. Schroeder, David A. Ewoldt, Isaac H. Wildeson, Robert Colby, Patrick R. Cantwell and Vijay Rawat; Eric A. Stach, an associate professor of materials engineering; and Sands.

 

Writer: Emil Venere, (765) 494-4709, venere@purdue.edu

 

Sources: Timothy Sands, (765) 496-6105, tsands@purdue.edu

 

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

Note to Journalists: An electronic copy of the research paper is available from Emil Venere, Purdue News Service, at (765) 494-4709, venere@purdue.edu

PHOTO CAPTION:
Timothy D. Sands, at left, director of Purdue’s Birck Nanotechnology Center in Discovery Park, and graduate student Mark Oliver, operate a “reactor” in work aimed at perfecting solid-state lighting, a technology that could cut electricity consumption by 10 percent if widely adopted. Inside the reactor, a material called gallium nitride is deposited on silicon at  temperatures of about 1,000 degrees Celsius, or 1,800 degrees Fahrenheit. Purdue researchers have overcome a major obstacle in reducing the cost of the lighting technology, called light-emitting diodes . (Purdue News Service photo/David Umberger)

A publication-quality photo is available at http://news.uns.purdue.edu/images/+2008/sands-LEDs.jpg

 


ABSTRACTOrganometallic Vapor Phase Epitaxial Growth of GaN on ZrN/AlN/Si Substrates

An intermediate ZrN/AlN layer stack that enables the epitaxial growth of GaN on (111) silicon substrates using conventional organometallic vapor phase epitaxy at substrate temperatures of 1000 °C is reported. The epitaxial (111) ZrN layer provides an integral back reflector and Ohmic contact to n-type GaN, whereas the (0001) AlN layer serves as a reaction barrier, as a thermally conductive interface layer, and as an electrical isolation layer. Smooth (0001) GaN films less than 1 micron thick grown on ZrN/AlN/ Si yield 0002 x-ray rocking curve full-width-at-half-maximum values as low as 1230 arc sec. © 2008 American Institute of Physics

 

Mark H. Oliver,1,3,a Jeremy L. Schroeder,1,3 David A. Ewoldt,1,3 Isaac H. Wildeson,1,2, Vijay Rawat,1,3 Robert Colby,1,3 Patrick R. Cantwell,1,3 Eric A. Stach,1,3
and Timothy D. Sands 1,2,3

1School of Materials Engineering, Purdue University,
West Lafayette, Indiana

2 School of Electrical and Computer Engineering,
Purdue University

3Birck Nanotechnology Center, Purdue University

 

July 7, 2008

Building a better heat sink and mass producing nanotube circuits

From KurzweilAI.net — amazing advances in chip-cooling tech removes 1K watts per square centimeter and nanotube-laden integrated circuits become economical.

Chip-cooling Technology Achieves ‘Dramatic’ 1,000-watt Capacity
Science Daily, July 2, 2008

Purdue University researchers have developed a technology that uses “microjets” to deposit liquid into tiny channels and remove five times more heat (1,000 watts per square centimeter) than other experimental high-performance chip-cooling methods for computers and electronics.

 
Read Original Article>>

Engineers show nanotube circuits can be made en masse
Nanowerk News, July 4, 2008

Stanford electrical engineers have developed a method for making integrated circuit chips with the needed variety of logic gates on the scale and with the parallelism that the semiconductor industry must employ to make chips that are economical.

The Stanford-devised process involves growing nanotubes on a quartz wafer and then transferring them onto a silicon wafer patterned with metal electrodes. The nanotubes could then connect the electrodes to make transistors and logic gates.

 
Read Original Article>>

April 9, 2008

Study shows Buckyballs don’t harm microbes

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 5:16 pm

I found this Nanowerk article via KurzweilAI.net. A Purdue University study found large numbers of Buckyballs don’t harm environment clean-up microbes. The study eases concerns that large amounts of the nanoparticle might be harmful if released into the environment.

From the link:

Nanowerk News) Even large amounts of manufactured nanoparticles, also known as Buckyballs, don’t faze microscopic organisms that are charged with cleaning up the environment, according to Purdue University researchers.
In the first published study to examine Buckyball toxicity on microbes that break down organic substances in wastewater, the scientists used an amount of the nanoparticles on the microbes that was equivalent to pouring 10 pounds of talcum powder on a person. Because high amounts of even normally safe compounds, such as talcum powder, can be toxic, the microbes’ resiliency to high Buckyball levels was an important finding, the Purdue investigators said.
The experiment on Buckyballs, which are carbon molecules C60, also led the scientists to develop a better method to determine the impact of nanoparticles on the microbial community.
“It’s important to look at the entire microbial community when nanomaterials are introduced because the microbes are all interdependent for survival and growth,” said Leila Nyberg, a doctoral student in the School of Civil Engineering and the study’s lead author. “If we see a minor change in these microorganisms it could negatively impact ecosystems.”
The microbes used in the study live without oxygen and also exist in subsurface soil and the stomachs of ruminant animals, such as cows and goats, where they aid digestion.
“We found no effect by any amount of C60 on the structure or the function of the microbial community over a short time,” Nyberg said. “Based on what we know about the properties of C60, this is a realistic model of what would happen if high concentrations of nanoparticles were released into the environment.”

April 2, 2008

Nanotech news in computing, display and medicine

The latest in nanotechnology developments from KurzweilAI.net.

First up is a variant of multidimensional hypercubes to be used as part of nanocomputers.

Next is an active-matrix display created with nanowires. This tech should eventually lead to e-paper, flexible monitors and other cool display applications.

Last is a nanomachine that kills cancer cells. UCLA researchers created a “nanoimpeller” that delivers anti-cancer drugs right to the cancer cell.

Hypercubes Could Be Building Blocks of Nanocomputers
PhysOrg.com, April 1, 2008University of Oklahoma researchers have investigated a new variant of multidimensional hypercubes as computational elements of nanocomputers: the “M-hypercube,” which could provide a higher-dimensional layout to support three-dimensional integrated circuits and the quantum properties of nanocomputers.The unique structure of hypercubes provides a massively parallel, distributed processing architecture with simple, robust communication linkages, able to count single electrons, and allow for parallel computing, reversibility, locality, and a three-dimensional architecture.

M-hypercubes contain two types of nodes: state nodes, which are embedded on the vertices of the M-hypercubes; and transmission nodes, which are embedded in the middle of the links between state nodes. Each node can be turned on or off; the transmission nodes can isolate parts of the cube from other parts when in the off state.

Read Original Article>>

Engineers make first ‘active matrix’ display using nanowires
PhysOrg.com, March 31, 2008Purdue University researchers have created the first active-matrix display using a new class of transparent nanowire transistors and circuits.Future applications include e-paper, flexible color monitors, and heads-up displays embedded in car windshields.
Read Original Article>>
Nanomachine kills cancer cells
PhysOrg.com, April 1, 2008UCLA researchers have developed a “nanoimpeller” nanomachine that stores anticancer drugs inside pores and then releases them into cancer cells in response to light.They claim it’s the first light-powered nanomachine that operates inside a living cell.

The interior of the pores are coated with azobenzene, a chemical that oscillates between two different shapes upon light exposure. The amount of drug released can be precisely controlled by the light‘s intensity, excitation time and specific wavelength.
Read Original Article>>

March 6, 2008

3D image of live virus captured

From KurzweilAI.net, the captured 3D image of a live virus.

New technique takes a big step in examination of small structures
KurzweilAI.net, March 6, 2008Researchers from Purdue University, Baylor College of Medicine, and MIT captured a three-dimensional image of a live virus at a resolution of 4.5 angstroms, tracing for the first time the polypeptide chain structure of a live virus.


bacteriophage Epsilon15

The technique used, single-particle electron cryomicroscopy, maintains the sample in a natural state. X-ray crystallography, for example, requires the sample to be crystallized.

Purdue University News Release