Flat Lens Boost Virtual Reality

Metalensesflat surfaces that use nanostructures to focus light — promise to revolutionize optics by replacing the bulky, curved lenses currently used in optical devices with a simple, flat surface.  But, these metalenses have remained limited in the spectrum of light they can focus well Now a team of researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has developed the first single lens that can focus the entire visible spectrum of light — including white light — in the same spot and in high resolution. This has only ever been achieved in conventional lenses by stacking multiple lenses.

Focusing the entire visible spectrum and white light – combination of all the colors of the spectrum — is so challenging because each wavelength moves through materials at different speeds. Red wavelengths, for example, will move through glass faster than the blue, so the two colors will reach the same location at different times resulting in different foci. This creates image distortions known as chromatic aberrations.

Cameras and optical instruments use multiple curved lenses of different thicknesses and materials to correct these aberrations, which, of course, adds to the bulk of the device.

Metalenses have advantages over traditional lenses,” says Federico Capasso, Professor of Applied Physics at SEAS and senior author of the research. “Metalenses are thin, easy to fabricate and cost effective. This breakthrough extends those advantages across the whole visible range of light. This is the next big step. Using our achromatic lens, we are able to perform high quality, white light imaging. This brings us one step closer to the goal of incorporating them into common optical devices such as cameras“.

The research is published in Nature Nanotechnology.

Source: https://www.seas.harvard.edu/

How To Generate Wonderful Colors

Colors are produced in a variety of ways. The best known colors are pigments. However, the very bright colors of the blue tarantula or peacock feathers do not result from pigments, but from nanostructures that cause the reflected light waves to overlap. This produces extraordinarily dynamic color effects.

blue-tarantulaScientists from Karlsruhe Institute of Technology (KIT) in Germany, in cooperation with international colleagues, have now succeeded in replicating nanostructures that generate the same color irrespective of the viewing angle.

In contrast to pigments, structural colors are non-toxic, more vibrant and durable. In industrial production, however, pigments have the drawback of being strongly iridescent, which means that the color perceived depends on the viewing angle. An example is the rear side of a CD. Hence, such colors cannot be used for all applications. Bright colors of animals, by contrast, are often independent of the angle of view. Feathers of the kingfisher always appear blue, no matter from which angle we look. The reason lies in the nanostructures: While regular structures are iridescent, amorphous or irregular structures always produce the same color. Yet, industry can only produce regular nanostructures in an economically efficient way. Radwanul Hasan Siddique, researcher at KIT in collaboration with scientists from USA and Belgium has now discovered that the blue tarantula does not exhibit iridescence in spite of periodic structures on its hairs. First, their study revealed that the hairs are multi-layered, flower-like structure. Then, the researchers analyzed its reflection behavior with the help of computer simulations. In parallel, they built models of these structures using nano-3D printers and optimized the models with the help of the simulations. In the end, they produced a flower-like structure that generates the same color over a viewing angle of 160 degrees. This is the largest viewing angle of any synthetic structural color reached so far.

Apart from the multi-layered structure and rotational symmetry, it is the hierarchical structure from micro to nano that ensures homogeneous reflection intensity and prevents color changes. Via the size of the “flower,” the resulting color can be adjusted, which makes this coloring method interesting for industry. “This could be a key first step towards a future where structural colorants replace the toxic pigments currently used in textile, packaging, and cosmetic industries,” says Radwanul Hasan Siddique of KIT’s Institute of Microstructure Technology, who now works at the California Institute of Technology. He considers short-term application in textile industry feasible. Dr. Hendrik Hölscher thinks that the scalability of nano-3D printing is the biggest challenge on the way towards industrial use. Only few companies in the world are able to produce such prints.

Source: http://www.kit.edu

Nano-enhanced Textiles Clean Themselves Of Stains

Researchers at RMIT University in Melbourne, Australia, have developed a cheap and efficient new way to grow special —which can degrade organic matter when exposed to lightdirectly onto . The work paves the way towards nano-enhanced textiles that can spontaneously clean themselves of stains and grime simply by being put under a light bulb or worn out in the sun. Dr Rajesh Ramanathan said the process developed  by the team had a variety of applications for catalysis-based industries such as agrochemicals, pharmaceuticals and natural products, and could be easily scaled up to industrial levels.

no more washing textileClose-up of the nanostructures grown on cotton textiles by RMIT University researchers. Image magnified 150,000 times

The advantage of textiles is they already have a 3D structure so they are great at absorbing light, which in turn speeds up the process of degrading organic matter,”said Dr Ramanathan. “There’s more work to do to before we can start throwing out our washing machines, but this advance lays a strong foundation for the future development of fully self-cleaning textile, he adds.”

The researchers from the Ian Potter NanoBioSensing Facility and NanoBiotechnology Research Lab at RMIT worked with copper and silver-based nanostructures, which are known for their ability to absorb visible light.

Source: http://phys.org/

Nanostructures For Hip and Knee Implants.

Scientists from the Research Center for Advanced Materials (CIMAV) in Mexico look for nanostructures that allow compatibility between metal, human bone tissues. Various scientific projects performed at the Cimav, Unit Monterrey, in the north of Mexico, aimed at one goal: conducting research and apply the knowledge in the development of biomedical implants, since the ones existing in the domestic market come generally from foreign manufacture. Currently this center, part of the National Council for Science and Technology (CONACYT) and located at the Park of Research and Technological Innovation (PIIT), works on the study of novel materials, coating systems and specific properties to use in the manufacture of hip and knee implants, and, in the future, of dental parts. It is the combination of research focused on nanostructured materials with biocompatible and antibacterial properties. In this regard, Ana Maria Arizmendi Morquecho, Cimav scholar, explains that the challenge is to find appropriate measures to improve the compatibility of a metal structure with the chemical composition of bone tissue and human bone’s nanostructures.
ceramic material compatible with the boneWe use a ceramic material which is compatible with the bone, in this case hydroxyapatite, which is used as a matrix and nanoparticles from other materials are used to reinforce it and provide improvements to the bicompatibility, joint wear and mechanical properties” , explains Arizmendi Morquecho
The biocompatibility is the ability of a material to be in contact with a living being without adverse effects, therefore represents one of the most important properties in the manufacture of a biomedical implant. Currently the knee and hip implants are complex systems made of titanium alloy substrates, which require a coating compatible with bone tissue and physiological fluids using nanotechnology; to achieve this intermediate coating deposition techniques of new synthesized materials are used”.

Source: http://www.cimav.edu.mx/