Penn Researchers Find New Way to Mimic the Color and Texture of Butterfly Wings

October 10, 2012

Yang's group has a new way of combining the structural color and superhydrophobicity found in butterfly wings (Credit: AFM)

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A drop of water sits on a material with structural color and superhydrophobicity. (Credit: AFM)

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Shu Yang

PHILADELPHIA — The colors of a butterfly’s wings are unusually bright and beautiful and are the result of an unusual trait; the way they reflect light is fundamentally different from how color works most of the time.

A team of researchers at the University of Pennsylvania has found a way to generate this kind of “structural color” that has the added benefit of another trait of butterfly wings: super-hydrophobicity, or the ability to strongly repel water.

The research was led by Shu Yang, associate professor in the Department of Materials Science and Engineering at Penn’sSchool of Engineering and Applied Science,and included other members of her group: Jie Li, Guanquan Liang and Xuelian Zhu.

Their research was published in the journalAdvanced Functional Materials.

“A lot of research over the last 10 years has gone into trying to create structural colors like those found in nature, in things like butterfly wings and opals,” Yang said.” People have also been interested in creating superhydrophobic surfaces which is found in things like lotus leaves, and in butterfly wings, too, since they couldn’t stay in air with raindrops clinging to them.”

The two qualities — structural color and superhydrophobicity — are related by structures. Structural color is the result of periodic patterns, while superhydrophobicity is the result of surface roughness

When light strikes the surface of a periodic lattice, it’s scattered, interfered or diffracted at a wavelength comparable to the lattice size, producing a particularly bright and intense color that is much stronger than color obtained from pigments or dyes.

When water lands on a hydrophobic surface, its roughness reduces the effective contact area between water and a solid area where it can adhere, resulting in an increase of water contact angle and water droplet mobility on such surface. 

While trying to combine these traits, engineers have to go through complicated, multi-step processes, first to create color-providing 3D structures out of a polymer, followed by additional steps to make them rough in the nanoscale. These secondary steps, such as nanoparticle assembly, or plasma etching, must be performed very carefully as to not vary the optical property determined by the 3D periodic lattice created in the first step.

Yang’s method begins with a non-conventional photolithography technique, holographic lithography, where a laser creates a cross-linked 3D network from a material called a photoresist. The photoresist material in the regions that are not exposed to the laser light are later removed by a solvent, leaving the “holes” in the 3D lattice that provides structural color.

Instead of using nanoparticles or plasma etching, Yang’s team was able to add the desired nano-roughness to the structures by simply changing solvents after washing away the photoresist. The trick was to use a poor solvent; the better a solvent is, the more it tries to maximize the contact with the material. Bad solvents have the opposite effect, which the team used to its advantage at the end of the photolithography step.

“The good solvent causes the structure to swell,” Yang said. “Once it has swollen, we put in the poor solvent. Because the polymer hates the poor solvent, it crunches in and shrivels, forming nanospheres within the 3D lattice.

“We found that the worse the solvent we used, the more rough we could make the structures,” Yang said.

Both superhydrophobicity and structural color are in high demand for a variety of applications. Materials with structural color could be used in as light-based analogs of semiconductors, for example, for light guiding, lasing and sensing. As they repel liquids, superhydrophobic coatings are self-cleaning and waterproof. Since optical devices are highly dependent on their degree of light transmission, the ability to maintain the device surface’s dryness and cleanliness will minimize the energy consumption and negative environmental impact without the use of intensive labors and chemicals. Yang has recently received a grant to develop such coatings for solar panels.

The researchers have ideas for how the two traits could be combined in one application, as well.

“Specifically, we’re interested in putting this kind of material on the outside of buildings,” Yang said. “The structural color we can produce is bright and highly decorative, and it won’t fade away like conventional pigmentation color dyes. The introduction of nano-roughness will offer additional benefits, such as energy efficiency and environmental friendliness.

“It could be a high-end facade for the aesthetics alone, in addition to the appeal of its self-cleaning properties. We are also developing energy efficient building skins that will integrate such materials in optical sensors.”

The research was supported by the Office of Naval Research and the National Science Foundation.

La Era del Diamante.

The unique atomic structure of diamonds will likely make them a vital cog in the next generation of high technology, bionic eyes to new lasers and tamper proof communications.

IN THE 1953 MOVIE, Gentleman Prefer Blondes, an ageing aristocrat called Sir Francis Beekman gave away his wife’s diamond tiara to gain the affections of Marilyn Monroe’s character Lorelei Lee. The movie’s hit song was "Diamonds are a girl’s best friend".

But nearly 60 years later, developments in the fields of physics and nanotechnology are proving that diamonds can be used for far more interesting things than plain old seduction.

In fact this physicist’s ‘new best friend’ is popping up all over the show and playing a starring role in new research into bionic eyes, delicate new lasers, tamper proof communication and prosthetic knees. According to David Awschalom, a quantum physicist at the University of California in Santa Barbara, we’re on the verge of 'the Diamond Age'.

It’s long been recognised that diamond is the hardest natural substance known. The Ancient Greeks called it ‘adamas’, which means ‘unconquerable and indestructible’.

Less well known is that diamond conducts heat faster than any other material, making it ideal for drawing waste heat away from energy intensive electronics.

Diamond is also virtually transparent through a wide spectrum of wavelengths ranging from ultraviolet to the far infrared. Light absorption only tends to occur because of impurities of boron or nitrogen in the tight crystal lattice of carbon atoms that makes up diamond.

Natural diamonds were formed millions of years ago in hot, high pressure environments more than 100 km beneath the Earth’s surface. But nowadays, diamonds can be grown in the lab in a process called chemical vapour deposition (CVD), which involves ionising a mixture of gases including methane.

As carbon is freed from the methane, it forms diamond on a specially prepared base material heated to 800°C. It’s also possible to ‘dope’ the diamond by adding elements such as boron or nitrogen to the recipe, in order to take advantage of its unique properties.

In fact, some of the most exciting opportunities in quantum technology today rely on these dopants within diamond. One such impurity occurs when a single nitrogen atom gets caught in the lattice of carbon atoms. It bonds with the diamond in such a way that an electron is left 'free'.

David Awschalom’s research focuses on manipulating the ‘spin’ of these free electrons with microwaves in a new field of research termed ‘spintronics’. Spin can be thought of as a magnetic property of elementary particles on a quantum level and electrons usually exist as spin up or spin down.

This is a natural fit with the concept of the ones and zeroes of the binary code on which modern digital computing is based. But due to the baffling rules of quantum mechanics, microwaves can be used to put the electron somewhere between spin up and spin down, as a combination of any number of different states.

The electron could thus become a way to store massive amounts of data, and it could also form the basis for quantum computers, which would use quantum effects to manipulate the data. This is predicted to greatly increase the speed of computers, because of the vast number of calculations that could occur on a single electron.

THE ADVANTAGE of using diamond for these operations is that the electrons are held firmly in place by the crystal, and are less vulnerable to environmental interference that would scramble their state. So the information stored on electrons in diamond remains in place for much longer than in other materials.

Importantly, in diamond this effect also exists at room temperature and Awschalom has been able manipulate the electron at high speeds, changing its state within a billionth of a second.

Awschalom says this will help move quantum technologies from the science lab into everyday life. “It's exciting to stand back and realise that we can already electrically control the quantum state of just a few atoms at gigahertz rates – speeds comparable to what you might find in your computer at home,” he says.

The impurities in diamond are also behind a revolutionary new form of communication that has been developed by Steven Prawer, a physicist at the Melbourne Materials Institute based at he University of Melbourne. “Diamond has a magical property, that some of the defects are so bright that you can see a single atom,” he says.

When stimulated by a short burst of light, the electron bound to an impurity absorbs energy, and then releases that energy a short time later by emitting a single photon. Prawer has managed to harness these photons for communication, either through fibre optic cable of simply through the air.

Amazingly, it is impossible to eavesdrop on this communication without destroying the signal.

“If you and I are talking along an optical fibre then we have pulses to give us our ones and zeroes,” says Prawer. “These pulses consist of a huge number of photons per pulse, so if someone wants to listen in on the line they can just snap on a gizmo that sucks some of the photons out of the optical fibre.

“Because there are so many photons per pulse, you and I would never know.”

But with Prawer’s system there’s only one photon per pulse and the information is carried in the polarisation of the photon. By the laws of quantum mechanics, any one who disturbs the signal also disrupts the polarity of the photons, destroying the information and alerting those on both ends of the call to the gatecrasher.

This concept has already been commercialised and work is currently underway to provide the Victorian Police Force in Australia with an ultra-secure communication system between various police headquarters.

Prawer is also recruiting diamond to create a bionic eye for Bionic Vision Australia. “Our goal is to create an electrode array that has about a thousand pixels, because a thousands pixels is the point at which you can just recognise faces and large print,” he says.

“Most of the blind people are telling us that’s what they miss the most.”

DIAMOND WAS the ideal candidate to create the array because in addition to its strength, the free electrons attached to the impurities in diamond allow it to act as a semi-conductor.

What’s more, diamond is made from carbon, which by a lucky coincidence, makes up 20% of our bodies too. This makes diamond ‘biocompatible’, meaning the body doesn’t reject it.

The plan is to implant the array behind the retinas of people blinded by degenerative eye diseases such as retinitis pigmentosa or age-related macular degeneration.

An electronic signal will pass from a camera, and through the diamond, to stimulate the ganglion nerves behind the retina, literally allowing the blind to see again. Prawer says that some lower resolution arrays should be implanted in humans by 2013.

xANOTHER AREA of medicine that could benefit from diamond is the field of prosthetics, due to an effect which seems to defy the laws of physics.

Prosthetics have a limited lifetime, and people who have knee replacements sometimes require another after 10 to 15 years. Coating the prosthetic in a thin layer of diamond could solve that, but the problem is the diamond might be abrasive to flesh.

Alexander Wissner-Gross, a theoretical physicist at Harvard University in Boston has performed computer simulations which show that adding a single layer of sodium atoms to the diamond could create a surface on which a layer of ice just a few molecules deep would persist well above body temperature.

Theoretically, the ice could then act as a lubricant, eliminating the harsh effects of the diamond.

He stresses his research was purely theoretical, but says there is evidence of ice layers at room temperature on other surfaces.

"There is very active experimental research," he says, "both in terms of the phase transition of ice in the presence of surfaces not too dissimilar from the type that we studied and the general physical properties of biocompatible yet hard finishings for joint replacements."

While many of the technological advances being made with diamond rely on their impurities, optical physicist Rich Mildren likes his diamonds pure. Using synthetic diamonds about 8 millimetres long, the Macquarie University researcher in Sydney has created a diamond laser that is the first of its kind.

Using high purity diamonds reduces the amount of waste produced by light passing through the material, which increases the power output that can be achieved. Dissipation of waste heat is critical in lasers and the extremely fast conduction rate of diamond is a major attraction for creating compact lasers of unprecedented output power.

A further major advantage of a diamond laser is that it can operate at infrared wavelengths that have been unobtainable with conventional lasers. One important application could be for lasers, with wavelengths around six to seven millionths of a metre, which would benefit neurosurgeons.

"There is a protein absorption band in that wavelength region," says Mildren. "A laser at that wavelength, with the right beam characteristics, has significant potential for enabling you to do very fine cuts in tissue, with precision approaching a single cell."

Another use for the diamond laser is tuning to the particular wavelength absorption bands of the vapours given off by explosives. This has obvious application in airports and warzones.

"The idea is to use the laser to sniff out explosive vapours from a remote and safe distance," says Mildren. "The laser beam return signal is affected by the absorbing vapour allowing any potential threats to be instantly visualized."

As physicists continue to find more and more uses for synthetic diamond, Mildren says there are more and more companies meeting this demand.

The price of the diamonds he uses is in the ballpark of diamonds one might buy in a jewellery store. "I wouldn’t be surprised if that drops quite significantly in the future," he says.

"It’s only carbon after all right?"

La Quimica del Boro

Boron naturally occurs in borax . It is isolated by reduction with magnesium Boron hydrides are the best fuels known. They are pyrophoric, however, and ignite upon contact with the atmosphere. In addition to being toxic, boron hydrides also yield high-mass B(OH)3 (s) as exhaust which does not provide good thrust. The molecule B12 is icosahedral. Boric acid decomposes as Boron Hydride (BH3) exists only as a reaction intermediate It is a Lewis acid which forms BH, BH4CO, BH4NH3. Diborane (B2H6) is a bridge-bonded compound: It decomposes at 200  as which are all 11-electron compounds. Additional reactions are (-2229 kJ mol-1) and (-1557 kJ mol-1). The compound B5H9 has C symmetry. The number of bonding electrons are which are allocated to bonds as The compound B4H10 is icosahedral (with 12 vertices and 20 faces), and undergoes  hybridization. B3N3H6 is cycloborane with N's and B's occupying alternate sites in the ring.

La Enzima de la Inmortalidad

Researchers investigating an enzyme which permits unlimited cell replication have received the Nobel Prize for Medicine. The enzyme is called telomerase. Telomerase affects telomeres, parts of cells which govern cell replication. According to Bloomberg, human genes are packed into chromosomes, which are topped by telomeres. Telomeres get shorter each time a cell divides -- except in cells with the telomerase enzyme. "When the caps get too short, the cell can’t divide anymore and dies. While the telomerase enzyme isn’t active in most human cells, which stop reproducing and eventually die, it has been found in cancer cells, the Nobel committee for the medicine prize said in a statement on its Web site." Telomeres, when discovered a decade ago, became a subject of intense scientific speculation. Their apparent capacity to define cell replication, naturally, was a subject of equally intense debate, and ways of manipulating them were considered in a menagerie of efforts ranging from the science fiction approach to the fatalistic. The prize was awarded to American researchers Elizabeth H. Blackburn, Carol W. Greider, and Jack W. Szostak. Articulo Completo aqui

Este video muestra una manera faci de comprender las telomerasas y la accion de estas en nuestro cuerpo

Harder , Better , Faster , Stronger & Smaller

¿1TB de capacidad de almacenamiento en una pequeña memoria ?

Actualmente las memorias flash mas grandes alcanzan capacidades de hasta 32GB , pero a un precio excesivo , esto podria estar a punto de cambiar una vez mas gracias a la nanotecnologia.

Esta nueva memoria es llamada PMC(por su nombre en ingles)  y este nombre hace referencia a Celda de Metalizacion programable y utiliza nanotecnologia para cargar particulas de cobre a escala molecular haciendola hasta 1,000 veces mas eficiente en cuanto a consumo de energia contra las memorias flash que existen hoy en dia. Por lo que se espera que este neuvo tipo de memoria se utilize en los dispositivos portatiles como ipods, celulares , laptops.
Probablemente esta sea la respuesta de las compañias que quieren implementar memorias de estado solido pero no lo hacen por ser caras , esta tecnologia es similar a los SSD pero mucho mas barata.

DNA Origami

El ADN es la estrutura primordial para la vida pues este define morfologia,comportamiento,color,etc de un organismo. Sin embargo el ADN desde su descubrimiento por Watson y Crick ah sido base para el estudio de la misma. Hoy en dia se investiga para crear nanomaquinaria utilizando ADN como andamio molecular para construir maquinaria nanoestructurada , haciendo uso de propiedades bastante utiles del adn como su habilidad de auto replicarse y autoensamblarse , podriamos imaginar que en un futuro el ADN y otros acidos nucleicos como ARN podrían servirnos para construir maquinara nanoestructurada de manera sencilla utilizando oligonucleotidos como grapas moleculares y así hacer dobleces donde fuese necesario para el diseño de la nanomaquina. Estas nanomaquinas no estarian gobernadas por motores, poleas , palancas y otras cosas con las que las maquinas a nivel macroscopico(autos,aviones,gruas) funcionan si no reaccionarian frente a ambientes quimicos como concentraciones de iones en solución acuosa , ph ,etc. De poder diseñar nanomaquinas con adn se podrian esperar en un futuro maquinara nanoestructurada que se auto ensamble y se auto replique por si sola . Para leer mas haz click aqui

Motor Electro unimolecular

Químicos en la universidad de Tufs han desarrollado el primer motor electrico funcional de una sola molecula , el cual se espera tenga aplicaciones en medicina y en dispositivos electronicos . El motor opero de manera correcta rotando hacia un lado u otro dependiendo de la corriente electrica aplicada en el mismo mediante el uso de un microscopio de fuerza atomica. Este primer motor de una sola molecula podria tener un gran impacto en el diseño de las primeras nanomaquinas.  Se utlizo el microscopio de fuerza atomica para para dar la corriente electrica a una molecula  sulfito de metil butil sobre una superficie de cobre conductor. Esta molecula de sulfuro tiene atomos de carbono y de hidrogeno que asemejan lo que parecen 2 brazos  con cuatro carbonos en cada lado , estas cadenas de carbono tienen libre rotacion de la molecula principal lo que permite su movimiento.
  Para leer la nota completa haz click aqui

Nanolistones de Grafeno

çDos grupos de investigadores han encontrado la forma de literalmente desdoblar nanotubos de carbono y asi crear nano listones de carbono. Se cree que estos pudieran desarrollar una nueva electronica haciendo uso de este material. Estos inclusive podrian tener mas aplicaciones que el grafeno puro pues estos se pueden doblar en estructuras mas pequeñas . Sin embargo estos listones han sido dificiles de sintetizar al igual que costosos en produccion. Estos nanolistones dr grafeno son altamente flexibles y conductores por lo que se planean aplicar para dispositivos electronicos flexibles. La nota completa Aqui.

New ultra-battery is the most powerful non-nuclear energy storage ever

What do you get when you combine some xenon, some fluoride, and pressures similar to those found at the center of the Earth? You get an ultra-battery, capable of storing more condensed energy than any other battery ever built.

The material used to make the "battery" is xenon difluoride (XeF₂), a white crystal primarily used to etch silicon conductors. The crystal was placed in a diamond anvil cell, a tiny device that measures only two inches by three inches. The cell uses two tiny diamond anvils (as you might expect, considering its name) to produce incredibly high pressures in tiny, contained spaces.

Normally, the molecules in xenon difluoride stay relatively far apart. The squeezing process the crystals underwent in the diamond anvil cell forced the molecules closer and closer together. At first, the squeezing caused the crystal to become a two-dimensional semiconductor, but then something even more remarkable happened. When the pressure reached a million atmospheres, similar to the pressure found halfway to the center of the Earth, the molecules formed 3D metallic "network structures", which forced all the mechanical energy of the compression process to be stored as chemical energy within the molecular bonds. At a million atmospheres, that's a whole lot of stored energy.

Heading up this research is Washington State chemistry professor Choong-Shik Yoo, who says this "is the most condensed form of energy storage outside of nuclear energy." The possible applications of the material pretty much all include the word "super": superconductors, super-oxidizing materials that can destroy chemical and biological agents, not to mention new fuels and, most obviously, an energy storage device.

Gel Touch Que se expande hasta 21 veces su tamaño.

September 05, 2012

Biocompatible material created at Harvard is much tougher than cartilage

Cambridge, Mass. - September 5, 2012 - A team of experts in mechanics, materials science, and tissue engineering at Harvard have created an extremely stretchy and tough gel that may pave the way to replacing damaged cartilage in human joints.
Called a hydrogel, because its main ingredient is water, the new material is a hybrid of two weak gels that combine to create something much stronger. Not only can this new gel stretch to 21 times its original length, but it is also exceptionally tough, self-healing, and biocompatible—a valuable collection of attributes that opens up new opportunities in medicine and tissue engineering.
The material, its properties, and a simple method of synthesis are described in the September 6 issue of Nature.

The researchers pinned both ends of the new gel in clamps and stretched it to 21 times its initial length before it broke. (Photo courtesy of Jeong-Yun Sun.)

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"Conventional hydrogels are very weak and brittle—imagine a spoon breaking through jelly," explains lead author Jeong-Yun Sun, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS). "But because they are water-based and biocompatible, people would like to use them for some very challenging applications like artificial cartilage or spinal disks. For a gel to work in those settings, it has to be able to stretch and expand under compression and tension without breaking."