Ultra-Simple Method for Creating

Nanoscale Gold Coatings Developed

Researchers at Rensselaer have developed a new, ultra-simple method for making layers of gold that measure only billionths of a meter thick. As seen in the research image, drops of gold-infused toluene applied to a surface evaporate within a few minutes and leave behind a uniform layer of nanoscale gold. The process requires no sophisticated equipment, works on nearly any surface, takes only 10 minutes, and could have important implications for nanoelectronics and semiconductor manufacturing. (Credit: Image courtesy of Rensselaer Polytechnic Institute)

Gold plated porche.Munich show.

Science (June 21, 2010) — Researchers at Rensselaer Polytechnic Institute have developed a new, ultra-simple method for making layers of gold that measure only billionths of a meter thick. The process, which requires no sophisticated equipment and works on nearly any surface including silicon wafers, could have important implications for nanoelectronics and semiconductor manufacturing.

Sang-Kee Eah, assistant professor in the Department of Physics, Applied Physics, and Astronomy at Rensselaer, and graduate student Matthew N. Martin infused liquid toluene — a common industrial solvent — with gold nanoparticles. The nanoparticles form a flat, closely packed layer of gold on the surface of the liquid where it meets air. By putting a droplet of this gold-infused liquid on a surface, and waiting for the toluene to evaporate, the researchers were able to successfully coat many different surfaces — including a 3-inch silicon wafer — with a monolayer of gold nanoparticles.

“There has been tremendous progress in recent years in the chemical syntheses of colloidal nanoparticles. However, fabricating a monolayer film of nanoparticles that is spatially uniform at all length scales — from nanometers to millimeters — still proves to be quite a challenge,” Eah said. “We hope our new ultra-simple method for creating monolayers will inspire the imagination of other scientists and engineers for ever-widening applications of gold nanoparticles.”

Results of the study, titled “Charged gold nanoparticles in non-polar solvents: 10-min synthesis and 2-D self-assembly,” were published recently in the journal Langmuir.

Whereas other synthesis methods take several hours, this new method chemically synthesizes gold nanoparticles in only 10 minutes without the need for any post-synthesis cleaning, Eah said. In addition, gold nanoparticles created this way have the special property of being charged on non-polar solvents for 2-D self-assembly.

Previously, the 2-D self-assembly of gold nanoparticles in a toluene droplet was reported with excess ligands, which slows down and complicates the self-assembly process. This required the non-volatile excess ligands to be removed in a vacuum. In contrast, Eah’s new method ensures that gold nanoparticles float to the surface of the toluene drop in less than one second, without the need for a vacuum. It then takes only a few minutes for the toluene droplet to evaporate and leave behind the gold monoloayer.

“The extension of this droplet 2-D self-assembly method to other kinds of nanoparticles, such as magnetic and semiconducting particles, is challenging but holds much potential,” Eah said. “Monolayer films of magnetic nanoparticles, for instance, are important for magnetic data storage applications. Our new method may be able to help inform new and exciting applications.”

Co-authors on the paper are former Rensselaer undergraduate researchers James I. Basham ‘07, who is now a graduate student at Pennsylvania State University, and Paul Chando ‘09, who will begin graduate study in the fall at the City College of New York.

The research project was supported by Rensselaer, the Rensselaer Summer Undergraduate Research Program, the National Science Foundation (NSF) Research Experiences for Undergraduates, and the NSF’s East Asia and Pacific Summer Institutes and Japan Society for the Promotion of Science.

Watch a video demonstration of this new fabrication process at: http://www.youtube.com/watch?v=nqkwM9o1s-w

Sourced & published by Henry Sapiecha

Natural Solar Collectors

On Butterfly Wings

Inspire More Powerful Solar Cells

ScienceDaily (Feb. 5, 2009) — The discovery that butterfly wings have scales that act as tiny solar collectors has led scientists in China and Japan to design a more efficient solar cell that could be used for powering homes, businesses, and other applications in the future.

In the study, Di Zhang and colleagues note that scientists are searching for new materials to improve light-harvesting in so-called dye-sensitized solar cells, also known as Grätzel cells for inventor Michael Grätzel. These cells have the highest light-conversion efficiencies among all solar cells — as high as 10 percent.

The researchers turned to the microscopic solar scales on butterfly wings in their search for improvements. Using natural butterfly wings as a mold or template, they made copies of the solar collectors and transferred those light-harvesting structures to Grätzel cells. Laboratory tests showed that the butterfly wing solar collector absorbed light more efficiently than conventional dye-sensitized cells. The fabrication process is simpler and faster than other methods, and could be used to manufacture other commercially valuable devices, the researchers say.

Sourced and published by Henry Sapiecha 15th April 2010

Apr 09

Posted by: Editor in COATINGS, INVENTIONS, MANUFACTURING, METALS 5 Comments »

Metal Conductive Rubber

Chemists Create Self-assembling

April 1, 2007 — Polymer chemists have created a flexible, indestructible material, called metal rubber, that can be heated, frozen, washed or doused with jet fuel, and still retain its electricity-conducting properties. To make metal rubber, chemists and engineers use a process called self-assembly. The material is repeatedly dipped into positively charged and negatively charged solutions. The positive and negative charges bond, forming layers that conduct electricity. Uses of metal rubber include bendy, electrically charged aircraft wings, artificial muscles and wearable computers.

Portable gadgets were meant to be taken on the move. Portable also means accidents and damage can happen. Now, imagine electronics that can take a beating and bounce back! It’s soon possible with a shocking new flexible, indestructible material, called metal rubber.

“You can heat it. You can freeze it. You can stretch it. You can douse it with jet fuel,” Jennifer Lalli, a polymer chemist at NanoSonic, Inc., in Blacksburg, Va., tells DBIS.

Abuse it, and metal rubber snaps back to its original shape. But the best part of this rubbery material? It conducts electricity just like metal and is also lightweight.

To make metal rubber, chemists and engineers use a process called self-assembly. The material is repeatedly dipped into positively charged and negatively charged solutions. The positive and negative charges bond, forming layers that conduct electricity.

“Electricity flows through metal rubber because there are little metal particles, and the electricity flows from little metal particle, to little metal particle, to little metal particle, between the two ends just like a piece of copper metal,” Rick Claus, a NanoSonic electrical engineer, tells DBIS.

The self-assembly process coats almost anything — even fabric can be made to carry electrical power. Lalli says you can wash the metal rubber textiles and they maintain electrical current.

Scientists are looking into uses of metal rubber like bendy, electrically charged aircraft wings and artificial muscles — and wearable computers. Abuse-resistant, flexible circuits, like cell phones, are still years away, but the future looks bright — and powerful — for bendable products.

BACKGROUND: Materials engineers and chemists at NanoSonic, Inc. have developed a way to produce lightweight electrically conductive textiles that won’t break or disintegrate when you wash or stretch them. This makes the textiles perfect for use in sensor-laden ’smart clothes.’ An important component is the company’s trademarked metal rubber, a substance that has the elasticity of rubber and ability of steel to conduct electricity/ NanoSonic’s metal rubber and e-textiles could find use in protective clothing; flexible antennae and circuits; flexible displays; electromagnetic shielding; biomedical sensors and health monitoring; and applications in outer space.

HOW IT’S MADE: Instead of just mixing different materials together, like in a blender or weaving metal wire components into fabrics, NanoSonic’s manufacturing technique is a bit like ‘growing’ textiles in a makeshift washing machine. It’s called “electrostatic self-assembly.” By dipping the base material into baths of alternating electrons and protons, those nanoparticles with opposite charges attract and stick to each other like Velcro. So many different properties can be linked together without the material falling apart when it is washed or stretched. Each dip adds one layer. The e-textiles are lower in weight, with lower manufacturing costs and few byproducts, plus they can withstand repeated washings without falling apart.

EXAMPLES: In combat conditions, a US solder clothed in layers of garments made from e-textiles could wear sensors close to the skin that monitor blood pressure, body temperature, and heart rate. Another layer could be integrated into the Kevlar vest to register impact from a bullet or shrapnel. And sensors in an outer garment could ’sniff’ the air for toxic agents of chemical or biological warfare. It might also be possible to make a thicker but lightweight conductive fabric for electric power workers that would not limit their range of motion, but would reduce the effects of electric power line radiation.

ABOUT SELF-ASSEMBLY: There are two basic ways to manipulate matter. On the large scale, we pick things up with our hands and physically put them together. Nature uses self-assembly, assembling its structures molecule by tiny molecule. Spread out in a liquid, the miniature parts jostle about and come together in random configurations, gradually matching up through trial and error according to shape and electrical charges. It’s as if you shook a box holding the pieces of a jigsaw puzzle, and looked in to find the puzzle had assembled itself. Yet biological systems, as well as several inorganic physical systems, exhibit self-assembling or self-ordering behavior all the time.

Sourced and published by Henry Sapiecha 9th April 2010


Shark-Inspired Boat Surface

Materials Engineers Turn to Ferocious

Fish for Nonstick Ship Coating

May 1, 2005 — Researchers are using shark skin as a model for creating new coatings that prevent adhesion of algae and barnacles to boats. The new coating is modeled after sharks’ placoid scales, which have a rectangular base embedded in the skin with tiny spines or bristles that poke up from the surface that prevent things from attaching to the shark’s skin.

GAINESVILLE, Fla.–In the boating industry, a huge problem exists that can be summed up in three words — algae, barnacles and slime. Until now, the only way to prevent these organisms from growing was toxic paint. But researchers are studying a more natural approach that’s inspired by the ocean’s fiercest predator.

In movies, they’re the enemy, but in the world of science, sharks are allies.

Materials engineer Tony Brennan, of University of Florida in Gainesville, uses shark skin as a model for creating new surfaces. “The shark scales have a roughness that approximates the roughness that we had predicted would be a good roughness to stop adhesion,” he says.

Brennan designed the surfaces to prevent algae and barnacles from growing on boats. He says, “We started making surfaces that are mimicking the shark’s skin.”

A computer program helped researchers create the pattern and structure…

“Whatever we can draw, we can make into a surface,” says UF graduate student, Jim Schumacher.

And just like shark skin, spores can’t fit in the ridges and don’t want to balance on top of the surface Brennan and his team designed in the lab. “That’s a tremendous benefit to energy consumption, dollars and maintenance,” Brennan says.

Getting rid of those barnacles and other organisms would mean less cleaning and not having to drag around the extra weight would lower fuel costs.

“If it’s effective, it would tremendously affect the industry,” Emerson says.

When the surface hits the market in the next year, it could impact private boaters and Navy vessels, too. Researchers are also studying the shark-coated surface for medical applications.

In addition to being very thick — as much as four inches in some species — shark skin is made up of tiny rectangular scales topped with even smaller spines or bristles, making the skin rough to the touch.

Shark skin was used in the past as an abrasive, for polishing wood. In Asia, it was used to decorate sword hilts. In the South Pacific, natives used it for the membranes on drums. Even today, because shark skin is so tough and pliable, it is used to make fine leather goods, including purses, shoes, boots and wallets.

Shark skin is covered with tiny scales, known as placoid scales. These scales resemble small shark teeth in both appearance and structure: there is an outer layer of enamel, dentine, and a central pulp cavity. (Biologists call them “dermal denticles,” which literally translates into “tiny skin teeth.”)

Sharks essentially have a built-in suit of chain mail armor that doesn’t make them too stiff to move. The scales move and flex as the shark swims.

The shark skin’s dentine layer is made of a hard, crystalline material, which is embedded in a soft protein. This is important because embedding a hard material inside a softer one combines the best properties of both: a material that is rigid without being brittle.

The structure of shark skin has another function besides protection. The streamlined shape of the scales decreases the friction of the water flowing along the shark’s body by channeling it through grooves. The grooves are so closely spaced, they prevent eddies from coming into contact with the surface of the shark’s moving body. This reduces the amount of “drag” as the shark swims, enabling the creature to glide farther on a given amount of energy. Scientists have found that the ridges created by shark scales can reduce drag in the water by as much as 8 percent. Golf balls and many military aircraft and vessels employ similar drag-reducing principles.

Sourced and published by Henry Sapiecha 9th April 2010