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Images pop right up out of a mobile device that can be seen without special glasses

World's Thinnest Hologram Promises 3D Images on Our Mobile Phones

Holograms have fascinated onlookers for over half a century. But the devices for producing these holographic images have been relatively bulky contraptions, forced into their large size in part by the wavelengths of light that are necessary to generate them.

Emerging technologies such as plasmonics and metamaterials have offered a way to manipulate light in such a way that these wavelengths can be shrunk down. This makes it possible to use light for devices such as integrated photonic circuits. And just this week, we’ve seen metasurfaces enable an elastic hologram that can switch images when stretched.

Now, a team of researchers at RMIT University in Melbourne Australia and the Beijing Institute of Technology has developed what is being described as the “world’s thinnest hologram.” It is only 60 nanometers thick; they produced it not by using either plasmonics or metamaterials, but with topological insulators. The resulting technology could enable future devices capable of producing holograms that can be seen by the naked eye, and are small enough to be integrated into our mobile devices.

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Water splitting device in which the solar collecting element can be angled

Artificial Photosynthesis Moves on From Water Splitting to CO<sub>2</sub> Reduction

The road toward commercial artificial photosynthesis has been a bumpy one. Stories like the so-called artificial leaf generated a lot of hype in 2011, but the company initially behind the technology—Sun Catalytix—soon abandoned their commercial efforts in 2012 when it became clear the economics simply did not add up.

While other companies that launched around this time, Hypersolar for example, have continued to try to make their technology work commercially,  the scientific community seemingly has had far better luck advancing the fundamental science of photoelectrochemical reduction.

This scientific effort largely has been organized in the United States under the Department of Energy’s Joint Center for Artificial Photosynthesis (JCAP).  IEEE Spectrum had the opportunity to sit down with scientists at the northern branch of JCAP, located at Berkeley National Laboratory. (The southern arm is at the California Institute of Technology in Pasadena.) Our discussion covered where the technology is at this point, what’s next, and how nanomaterials are helping to shape its development.

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Image: University of Pennsylvania/American Chemical Society

Elastic Hologram Can Switch Images When Stretched

New elastic holograms can switch the images they display as they get stretched, finds a new study by scientists at the University of Pennsylvania. These holograms could have applications in virtual reality, flat-panel displays, and optical communications, researchers say.

Conventional holograms are photographs that, when illuminated, essentially turn into 2D windows looking at 3D scenes. The pixels of each hologram scatter light waves falling onto them, making the light waves interact with each other to generate an image with the illusion of depth.

Penn scientists in Philadelphia had previously created holograms made of gold rods only nanometers or billionths of a meter large embedded within elastic films of silicone rubber. These new holograms are a kind of metasurface, which manipulate light using structures smaller than wavelengths of light.

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Photo of Stefano Cabrini, head of nanofabrication at The Molecular Foundry

Novel Technique Stamps Out Nanoprobes

One of the cornerstones of the U.S. National Nanotechnology Initiative was the establishment of nanotechnology research facilities that would be available to outside users.  One of the five user facilities operated by the U.S. Department of Energy (DOE) is located at Berkeley National Lab and is known as The Molecular Foundry.

In a visit to The Molecular Foundry, we had the opportunity to discuss the state of nanofabrication with Stefano Cabrini, who is the director of its nanofabrication facility. “The mission of The Molecular Foundry is dedicated to nanoscience in general, but it is a user facility,” Cabrini told IEEE Spectrum. “So we are hosting here people from all over the world, from companies and from academia, from Europe, from Asia, from everywhere. They come here to work with us, to use or our instruments and facilities, but also to have access to our expertise.”

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SEM image of patterned PHCs

Photonic Hypercrystals Are Now a Reality, and Light Will Never Be the Same

In 2014, researchers  predicted the theoretical existence of a strange new material that altered the interaction between light and matter. The material, dubbed photonic hypercrystal, has now become a reality.

Researchers at the City College of New York (CCNY) say they have actually created some, and the realization of these materials could yield big changes in applications including light-based technologies such as solar cells and Li-Fi, where visible light from light emitting diodes provides a means of communication (essentially doing what Wi-Fi does, but with flashes of light instead of radio waves) and quantum information processing.

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The newly-developed smart lenses with built-in pressure-sensing and glucose-monitoring sensors.

Smart Contact Lens Detects Diabetes and Glaucoma

While tech giant Google continues to struggle to make a contact lens for monitoring diabetes, researchers at Ulsan National Institute of Science and Technology (UNIST) in South Korea have offered up at least one part of the puzzle: better wearability. Through the use of a hybrid film made from graphene and silver nanowires, the UNIST researchers have made contact lenses for detecting multiple biomarkers that are clear and flexible.

In research described in the journal Nature Communications, the UNIST researchers used graphene-nanowire hybrid films to serve as conducting, transparent, and stretchable electrodes. While the hybrid film alone does not perform any detection, the electrodes do ensure that the electrodes in the contact lenses don’t obscure vision and that they’re flexible enough to make wearing the lenses comfortable.

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New research allows sound frequencies to be mixed together, amplified and equalized - all within the same millimeter-sized device.

Graphene Speaker Produces Sound and Mixes Frequencies Simultaneously

The history of using nanomaterials such as magnetic nanoparticles or carbon nanotubes in audio speakers has mainly been to demonstrate the capabilities of these materials rather than to yield speakers that will actually be listened to. That changed last year when South Korean researchers used graphene to produce a speaker that does not require an acoustic box to produce sound.

Now researchers from the University of Exeter in the UK are turning again to graphene to make a speaker that produces sound thermoacoustically. Instead of depending on vibrations of a material inside of an acoustic box, thermoacoustics leverages a century-old idea that sound can be produced by the rapid heating and cooling of a material. Where the Exeter researchers’ work departs from that of their Korean counterparts is that this newest device serves not only as a speaker, but also as an amplifier and graphic equalizer—all on a thumbnail-size chip.

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A schematic showing a focused electron beam (green) shining through a polymeric film (grey: carbon atoms; red: oxygen atoms; white: hydrogen atoms).

Lithographic Feature Sizes Reduced to One Nanometer

Scientists at the U.S. Department of Energy’s (DOE) Center for Functional Nanomaterials (CFN) at Brookhaven National Laboratory have established a new record in reducing lithographic feature sizes using electron-beam lithography (EBL), which involves exposing an electron-sensitive material to a focused beam of electrons.

In their latest research, described in the journal Nano Letters, the CFN team performed electron beam lithography with a scanning transmission electron microscope (STEM) to bring individual feature sizes of patterns on polymer poly (methyl methacrylate)—or PMMA—down to one nanometer. The spaces between these features were only 11 nanometers. This brings areal density—a measure of the quantity of information bits that can be stored on a given area of surface—to nearly one trillion per square centimeter.

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Progressively thinner flakes of a van der Waals material

2D Materials Go Ferromagnetic, Creating a New Scientific Field

Researchers at the Lawrence Berkeley National Laboratory have successfully demonstrated that two-dimensional (2D) layered crystals held together by van der Waal forces—these include graphene and molybdenum disulfide—can exhibit intrinsic ferromagnetism. Not only did the team demonstrate that it exists in these materials, but the researchers also demonstrated a high degree of control over that ferromagnetism. The discovery could have a profound impact for applications including magnetic sensors and the developing use of spintronics for encoding information.

In research described in the journal Nature, the Berkeley scientists worked with a 2D chalcogenide layered material called chromium germanium telluride (CGT), a layered ferromagnetic insulator that has garnered interest because of its potential in spintronic devices. While the material has been around in bulk form for decades, only recently has it been made into 2D flakes, joining the list of other van der Waals crystals.

The researchers used an optical technique known as the magneto-optic Kerr effect that involves the use of a scanning Kerr optical microscope to observe the material. This technique detects how the rotation of linearly polarized light is changed when it interacts with electron spins in the material. This made it possible to detect unambiguously that the magnetism was originating from the atomically thin materials. 

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A rubber disk with a reflective copper center

Graphene Makes Infinite Copies of Compound Semiconductor Wafers

Despite graphene’s amazing properties and all the engineering that has gone into giving the wonder material a band gap, its prospects for digital logic remain as much in doubt as they have ever been.

But the list of uses for graphene in electronics outside of digital logic continues to grow. The latest comes from research out of MIT in which graphene could make the use of exotic semiconductors more accessible to industries by preparing semiconductor thin films without the high cost of using bulk wafers of the materials.

In research described in the journal Nature, a thin film of graphene is placed on top of a gallium arsenide (GaAs) wafer. Then compound semiconductors—which are made of more than one element such as gallium arsenide (GaAs), indium phosphide (InP) and indium gallium arsenide (InGaAs)—are grown on top of that graphene layer in an epitaxy process.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
Contributor
Rachel Courtland
New York City
 
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