Science

Scientists at the University of Buffalo have created a prototype visible light “hyperlens” that may help image objects that were once only clearly viewable through electron microscopes (Credit: University of Buffalo)

Using visible light magnified through a compound series of lenses to image small objects, standard optical microscopes have been with us for many centuries. Whilst continually being improved, the result of these many advances of optics and image-capturing techniques means that many high-end optical microscopes have now reached the limit of magnification possible as they push the resolution properties of light itself. In an attempt to resolve this issue, scientists at the University of Buffalo (UB) have created a prototype visible light “hyperlens” that may help image objects once only clearly viewable through electron microscopes.

The resolution limit for images captured by an optical microscope system is due to the diffraction of light from a viewed object. Put simply, as light passes through the circular aperture of a microscope lens, the light waves from very small points of light interfere with each other on the way through, causing the image to blur.

The diffraction problem is due to a phenomenon known as the “Rayleigh criterion”, which specifies the minimum separation distance between two observed objects that can be resolved into distinct objects. As the size of the aperture used in relation to the wavelength of light is inherent in the criterion’s formula, then the smaller the aperture and the closer in size an object is to the wavelength of light itself, the greater the diffraction and the more the image is blurred.

UB researchers working on metamaterials – that is, artificial materials engineered with properties not yet found in nature – claim to have overcome this diffraction limit problem by creating a photonic hyperlens that they say changes evanescent waves of light into propagating waves. In other words, they use these lenses to alter the properties of light from that which loses intensity rapidly (evanescent waves) to those that are increased in intensity (propagating waves).

The metamaterial hyperlenses first developed were made of silver and a dielectric insulating material arranged in concentric rings. Whilst this type of hyperlens worked very well at specific wavelengths of light, it suffered from large losses at resonant frequencies.

To help improve on this, UB researchers arranged minute slices of gold and PMMA (a clear thermoplastic) into a radiating semi-circular shape that the researchers point out looks like a very tiny Slinky suspended in its movement. This new shape turned out to be a much improved one, as it effectively ameliorates the diffraction limit on objects viewed in the visible light range.

An immediate use for such a device, the team believes, is that it could be combined with an optical waveguide to produce a hyperlens-based medical endoscope. As even high-resolution endoscopes can only resolve images of objects around 10,000 nanometers in size, a hyperlens-equipped endoscope could potentially increase that resolution to at least 250 nanometers or more, and may provide medical practitioners with that ability to locate tiny, hard-to-find cancers that could help catch the disease before it has time to spread.

“There is a great need in healthcare, nanotechnology and other areas to improve our ability to see tiny objects that elude even the most powerful optical systems,” said Natalia Litchinitser, PhD, professor of electrical engineering at UB. “The hyperlens we are developing is, potentially, a giant step toward solving this problem.”

The researchers also believe that the hyperlens may even eventually be capable of imaging single molecules in visible light, which has enormous implications for research in many fields, particularly chemistry and biology. In the field of physics, such a lens may also help such things as optical nanolithography, where light is shone through a mask to create a pattern on polymer or graphene films for integrated circuits, along with developments in the next generation of optoelectronic electronics, including sensors and data storage drives.

References: http://www.gizmag.com

Polysis is showing a plastic that can turn to clay when heated, according to a story on DigInfo TV. Polysis is described as a specialist developer of polyurethane resins and resin products, and they are marketing haplafreely, presented with a lower-case “h,” as a plastic that turns to clay when heated to temperatures above 60 degrees Centigrade.

Immerse the product in hot water—or heat it with a heat gun—and you find that the plastic is easy to shape, yet hardens again as it cools—and returns to its original hardness by the time it reaches room temperature.
Takato Mori, development division of Polysis, said the product remains in its clay state—staying malleable— five to 10 times longer than other products.”It also has a tensile strength,” he said, “three times greater than ordinary rubber, making it hard to break.”
It’s not difficult to peel off haplafreely; it won’t stick easily to other materials, according to DigInfo TV. It is softer than other plastics. As a cover material, it will not damage the product to which it is applied.
Promoted benefits include cutting costs. One does not have to think about thermal design or processing; the product can be formed into different shapes without them. “When heated, it will return to clay time and time again, making it ideal as a way of reducing costs in production line jigs.”
Real-world uses? The presentation suggested haplafreely as a cover for various components. Mori said haplafreely can be used to form bases on which to place unstable objects. For example, engine components need to be placed on a base for stability. Another case, he said, might be where motorcycle handlebars need to be worked on with a screwdriver. Haplafreey can be used in large quantities for protective covering.

Polysis is currently selling haplafreely in sheets measuring 40cm x 40cm and 4mm in thickness, and is aiming for monthly sales of 1,000 sheets, but haplafreely is also available in roll form, in thicknesses ranging from 0.6mm to 1.0mm.
The DigInfo TV report stated that “Polysis has received many requests from users for products that become soft at 70, 80 or 100°C, and will begin developing these this year.”
Commenting, Lee Mathews in Geek.com said the product was “noteworthy for its ability to become malleable with a minimal amount of heat applied.” He said haplafreely could make a difference on production lines. “If parts can be molded at a lower temperature, that means reduced energy use and shorter production times, which ultimately turns into either savings for you and me or higher profit margins for the producer. Or maybe even both.”

References:http://phys.org/

Even if you don’t know it by name, everyone is familiar with Newton’s third law, which states that for every action, there is an equal and opposite reaction. This idea can be seen in many everyday situations, such as when walking, where a person’s foot pushes against the ground, and the ground pushes back with an equal and opposite force. Newton’s third law is also essential for understanding and developing automobiles, airplanes, rockets, boats, and many other technologies.

Even though it is one of the fundamental laws of physics, Newton’s third law can be violated in certain nonequilibrium (out-of-balance) situations. When two objects or particles violate the third law, they are said to have nonreciprocal interactions. Violations can occur when the environment becomes involved in the interaction between the two particles in some way, such as when an environment moves with respect to the two particles. (Of course, Newton’s law still holds for the complete “particles-plus-environment” system.)

Although there have been numerous experiments on particles with nonreciprocal interactions, not as much is known about what’s happening on the microscopic level—the statistical mechanics—of these systems.

In a new paper published in Physical Review X, Alexei Ivlev, et al., have investigated the statistical mechanics of different types of nonreciprocal interactions and discovered some surprising results—such as that extreme temperature gradients can be generated on the particle scale.

“I think the greatest significance of our work is that we rigorously showed that certain classes of essentially nonequilibrium systems can be exactly described in terms of the equilibrium’s statistical mechanics (i.e., one can derive a pseudo-Hamiltonian which describes such systems),” Ivlev, at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, told Phys.org. “One of the most amazing implications is that, for example, one can observe a mixture of two liquids in detailed equilibrium, yet each liquid has its own temperature.”

One example of a system with nonreciprocal interactions that the researchers experimentally demonstrated in their study involves charged microparticles levitating above an electrode in a plasma chamber. The violation of Newton’s third law arises from the fact that the system involves two types of microparticles that levitate at different heights due to their different sizes and densities. The electric field in the chamber drives a vertical plasma flow, like a current in a river, and each charged microparticle focuses the flowing plasma ions downstream, creating a vertical plasma wake behind it.

Although the repulsive forces that occur due to the direct interactions between the two layers of particles are reciprocal, the attractive particle-wake forces between the two layers are not. This is because the wake forces decrease with distance from the electrode, and the layers are levitating at different heights. As a result, the lower layer exerts a larger total force on the upper layer of particles than the upper layer exerts on the lower layer of particles. Consequently, the upper layer has a higher average kinetic energy (and thus a higher temperature) than the lower layer. By tuning the electric field, the researchers could also increase the height difference between the two layers, which further increases the temperature difference.

“Usually, I’m rather conservative when thinking on what sort of ‘immediate’ potential application a particular discovery (at least, in physics) might have,” Ivlev said. “However, what I am quite confident of is that our results provide an important step towards better understanding of certain kinds of nonequilibrium systems. There are numerous examples of very different nonequilibrium systems where the action-reaction symmetry is broken for interparticle interactions, but we show that one can nevertheless find an underlying symmetry which allows us to describe such systems in terms of the textbook (equilibrium) statistical mechanics.”

While the plasma experiment is an example of action-reaction symmetry breaking in a 2D system, the same symmetry breaking can occur in 3D systems, as well. The scientists expect that both types of systems exhibit unusual and remarkable behavior, and they hope to further investigate these systems more in the future.

“Our current research is focused on several topics in this direction,” Ivlev said. “One is the effect of the action-reaction symmetry breaking in the overdamped colloidal suspensions, where the nonreciprocal interactions lead to a remarkably rich variety of self-organization phenomena (dynamical clustering, pattern formation, phase separation, etc.). Results of this research may lead to several interesting applications. Another topic is purely fundamental: how one can describe a much broader class of ‘nearly Hamiltonian’ nonreciprocal systems, whose interactions almost match with those described by a pseudo-Hamiltonian? Hopefully, we can report on these results very soon.”

References: www.phys.org

Evolution has created in bees, butterflies, and beetles something optical engineers have been struggling to achieve for years—precisely organized biophotonic crystals that can be used to improve solar cells, fiber-optic cables, and even cosmetics and paints, a new Yale-led study has found.

The Yale team used high-intensity X-rays at the Argonne National Laboratory in Chicago to investigate color-producing nanostructures within hair-like structures that cover some species of butterflies, weevils and beetles, bees, and spiders and tarantulas. They found that the architecture of these nanostructures are identical to chemical polymers engineered by chemists and materials scientists, according to the report published May 14 in the journal Nano Letters.
Engineers, however, have had difficulty organizing these polymers in larger structures that would make them commercially feasible.
“These biophotonic nanostructures have the same shapes commonly seen in blends of large, synthetic, Lego-like molecules called block copolymers, developed by chemists,” said lead author Vinod Saranathan, former Yale graduate student and now faculty member at Yale-NUS College in Singapore.

These artificial nanostructures need to be an order of magnitude larger—such as that found in the scales of beetles and butterflies—in order to interfere with light and make saturated colors. Engineers, chemists, and physicists currently find it difficult to control the self-assembly of synthetic polymers to achieve the desired shape of molecules over a large area, Saranathan said.

“Arthropods such as butterflies and beetles, which have evolved over millions of years of selection, appear to routinely make these photonic nanostructures using self-assembly and at the desired optical scale just like in modern engineering approaches,” said Richard Prum, the William Robertson Coe Professor in the Department of Ecology and Evolutionary Biology and senior author of the paper.

References: www.phys.org