Category Archives: light

A plasmonic nanolaser operating at visible light frequencies using ‘dark lattice’ modes

Finnish scientists have created lasers made of nanoparticles according to a Jan. 3, 2017 news item on ScienceDaily,

Researchers at Aalto University, Finland are the first to develop a plasmonic nanolaser that operates at visible light frequencies and uses so-called dark lattice modes.

The laser works at length scales 1000 times smaller than the thickness of a human hair. The lifetimes of light captured in such small dimensions are so short that the light wave has time to wiggle up and down only a few tens or hundreds of times. The results open new prospects for on-chip coherent light sources, such as lasers, that are extremely small and ultrafast.

The laser operation in this work is based on silver nanoparticles arranged in a periodic array.

A Jan. 3, 2017 Aalto University press release (also on EurekAlert), which originated the news item, describes the work in more detail,

 In contrast to conventional lasers, where the feedback of the lasing signal is provided by ordinary mirrors, this nanolaser utilizes radiative coupling between silver nanoparticles. These 100-nanometer-sized particles act as tiny antennas. To produce high intensity laser light, the interparticle distance was matched with the lasing wavelength so that all particles of the array radiate in unison. Organic fluorescent molecules were used to provide the input energy (the gain) that is needed for lasing.

Light from the dark

A major challenge in achieving lasing this way was that light may not exist long enough in such small dimensions to be helpful. The researchers found a smart way around this potential problem: they produced lasing in dark modes.

“A dark mode can be intuitively understood by considering regular antennas: A single antenna, when driven by a current, radiates strongly, whereas two antennas — if driven by opposite currents and positioned very close to each other — radiate very little,” explains Academy Professor Päivi Törmä.

“A dark mode in a nanoparticle array induces similar opposite-phase currents in each nanoparticle, but now with visible light frequencies”, she continues.

“Dark modes are attractive for applications where low power consumption is needed. But without any tricks, dark mode lasing would be quite useless because the light is essentially trapped at the nanoparticle array and cannot leave”, adds staff scientist Tommi Hakala.

“But by utilizing the small size of the array, we found an escape route for the light. Towards the edges of the array, the nanoparticles start to behave more and more like regular antennas that radiate to the outer world”, tells Ph.D. student Heikki Rekola.

The research team used the nanofabrication facilities and cleanrooms of the national OtaNano research infrastructure.

The researchers have produced a video elucidating their research,

A revelatory soundtrack by Kevin MacLeod has been added to this video.

Finally, here’s a link to and a citation for the paper,

Lasing in dark and bright modes of a finite-sized plasmonic lattice by T. K. Hakala, H. T. Rekola, A. I. Väkeväinen, J.-P. Martikainen, M. Nečada, A. J. Moilanen & P. Törmä. Nature Communications  8, Article number: 13687 doi:10.1038/ncomms13687 Published 03 January 2017

This is an open access paper.

A biocompatible (implantable) micromachine (microrobot)

I appreciate the detail and information in this well written Jan. 4, 2017 Columbia University news release (h/t Jan. 4, 2016 Nanowerk; Note: Links have been removed),

A team of researchers led by Biomedical Engineering Professor Sam Sia has developed a way to manufacture microscale-sized machines from biomaterials that can safely be implanted in the body. Working with hydrogels, which are biocompatible materials that engineers have been studying for decades, Sia has invented a new technique that stacks the soft material in layers to make devices that have three-dimensional, freely moving parts. The study, published online January 4, 2017, in Science Robotics, demonstrates a fast manufacturing method Sia calls “implantable microelectromechanical systems” (iMEMS).

By exploiting the unique mechanical properties of hydrogels, the researchers developed a “locking mechanism” for precise actuation and movement of freely moving parts, which can provide functions such as valves, manifolds, rotors, pumps, and drug delivery. They were able to tune the biomaterials within a wide range of mechanical and diffusive properties and to control them after implantation without a sustained power supply such as a toxic battery. They then tested the “payload” delivery in a bone cancer model and found that the triggering of release of doxorubicin from the device over 10 days showed high treatment efficacy and low toxicity, at 1/10 of the standard systemic chemotherapy dose.

“Overall, our iMEMS platform enables development of biocompatible implantable microdevices with a wide range of intricate moving components that can be wirelessly controlled on demand and solves issues of device powering and biocompatibility,” says Sia, also a member of the Data Science Institute. “We’re really excited about this because we’ve been able to connect the world of biomaterials with that of complex, elaborate medical devices. Our platform has a large number of potential applications, including the drug delivery system demonstrated in our paper which is linked to providing tailored drug doses for precision medicine.”

I particularly like this bit about hydrogels being a challenge to work with and the difficulties of integrating both rigid and soft materials,

Most current implantable microdevices have static components rather than moving parts and, because they require batteries or other toxic electronics, have limited biocompatibility. Sia’s team spent more than eight years working on how to solve this problem. “Hydrogels are difficult to work with, as they are soft and not compatible with traditional machining techniques,” says Sau Yin Chin, lead author of the study who worked with Sia. “We have tuned the mechanical properties and carefully matched the stiffness of structures that come in contact with each other within the device. Gears that interlock have to be stiff in order to allow for force transmission and to withstand repeated actuation. Conversely, structures that form locking mechanisms have to be soft and flexible to allow for the gears to slip by them during actuation, while at the same time they have to be stiff enough to hold the gears in place when the device is not actuated. We also studied the diffusive properties of the hydrogels to ensure that the loaded drugs do not easily diffuse through the hydrogel layers.”

The team used light to polymerize sheets of gel and incorporated a stepper mechanization to control the z-axis and pattern the sheets layer by layer, giving them three-dimensionality. Controlling the z-axis enabled the researchers to create composite structures within one layer of the hydrogel while managing the thickness of each layer throughout the fabrication process. They were able to stack multiple layers that are precisely aligned and, because they could polymerize a layer at a time, one right after the other, the complex structure was built in under 30 minutes.

Sia’s iMEMS technique addresses several fundamental considerations in building biocompatible microdevices, micromachines, and microrobots: how to power small robotic devices without using toxic batteries, how to make small biocompatible moveable components that are not silicon which has limited biocompatibility, and how to communicate wirelessly once implanted (radio frequency microelectronics require power, are relatively large, and are not biocompatible). The researchers were able to trigger the iMEMS device to release additional payloads over days to weeks after implantation. They were also able to achieve precise actuation by using magnetic forces to induce gear movements that, in turn, bend structural beams made of hydrogels with highly tunable properties. (Magnetic iron particles are commonly used and FDA-approved for human use as contrast agents.)

In collaboration with Francis Lee, an orthopedic surgeon at Columbia University Medical Center at the time of the study, the team tested the drug delivery system on mice with bone cancer. The iMEMS system delivered chemotherapy adjacent to the cancer, and limited tumor growth while showing less toxicity than chemotherapy administered throughout the body.

“These microscale components can be used for microelectromechanical systems, for larger devices ranging from drug delivery to catheters to cardiac pacemakers, and soft robotics,” notes Sia. “People are already making replacement tissues and now we can make small implantable devices, sensors, or robots that we can talk to wirelessly. Our iMEMS system could bring the field a step closer in developing soft miniaturized robots that can safely interact with humans and other living systems.”

Here’s a link to and a citation for the paper,

Additive manufacturing of hydrogel-based materials for next-generation implantable medical devices by Sau Yin Chin, Yukkee Cheung Poh, Anne-Céline Kohler, Jocelyn T. Compton, Lauren L. Hsu, Kathryn M. Lau, Sohyun Kim, Benjamin W. Lee, Francis Y. Lee, and Samuel K. Sia. Science Robotics  04 Jan 2017: Vol. 2, Issue 2, DOI: 10.1126/scirobotics.aah6451

This paper appears to be open access.

The researchers have provided a video demonstrating their work (you may want to read the caption below before watching),

Magnetic actuation of the Geneva drive device. A magnet is placed about 1cm below and without contact with the device. The rotating magnet results in the rotational movement of the smaller driving gear. With each full rotation of this driving gear, the larger driven gear is engaged and rotates by 60º, exposing the next reservoir to the aperture on the top layer of the device.

—Video courtesy of Sau Yin Chin/Columbia Engineering

You can hear some background conversation but it doesn’t seem to have been included for informational purposes.

Stretchy optical materials for implants that could pulse light

An Oct. 17, 2016 Massachusetts Institute of Technology (MIT) news release (also on EurekAlert) by Emily Chu describes research that could lead to long-lasting implants offering preventive health strategies,

Researchers from MIT and Harvard Medical School have developed a biocompatible and highly stretchable optical fiber made from hydrogel — an elastic, rubbery material composed mostly of water. The fiber, which is as bendable as a rope of licorice, may one day be implanted in the body to deliver therapeutic pulses of light or light up at the first sign of disease. [emphasis mine]

The researchers say the fiber may serve as a long-lasting implant that would bend and twist with the body without breaking down. The team has published its results online in the journal Advanced Materials.

Using light to activate cells, and particularly neurons in the brain, is a highly active field known as optogenetics, in which researchers deliver short pulses of light to targeted tissues using needle-like fibers, through which they shine light from an LED source.

“But the brain is like a bowl of Jell-O, whereas these fibers are like glass — very rigid, which can possibly damage brain tissues,” says Xuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in MIT’s Department of Mechanical Engineering. “If these fibers could match the flexibility and softness of the brain, they could provide long-term more effective stimulation and therapy.”

Getting to the core of it

Zhao’s group at MIT, including graduate students Xinyue Liu and Hyunwoo Yuk, specializes in tuning the mechanical properties of hydrogels. The researchers have devised multiple recipes for making tough yet pliable hydrogels out of various biopolymers. The team has also come up with ways to bond hydrogels with various surfaces such as metallic sensors and LEDs, to create stretchable electronics.

The researchers only thought to explore hydrogel’s use in optical fibers after conversations with the bio-optics group at Harvard Medical School, led by Associate Professor Seok-Hyun (Andy) Yun. Yun’s group had previously fabricated an optical fiber from hydrogel material that successfully transmitted light through the fiber. However, the material broke apart when bent or slightly stretched. Zhao’s hydrogels, in contrast, could stretch and bend like taffy. The two groups joined efforts and looked for ways to incorporate Zhao’s hydrogel into Yun’s optical fiber design.

Yun’s design consists of a core material encased in an outer cladding. To transmit the maximum amount of light through the core of the fiber, the core and the cladding should be made of materials with very different refractive indices, or degrees to which they can bend light.

“If these two things are too similar, whatever light source flows through the fiber will just fade away,” Yuk explains. “In optical fibers, people want to have a much higher refractive index in the core, versus cladding, so that when light goes through the core, it bounces off the interface of the cladding and stays within the core.”

Happily, they found that Zhao’s hydrogel material was highly transparent and possessed a refractive index that was ideal as a core material. But when they tried to coat the hydrogel with a cladding polymer solution, the two materials tended to peel apart when the fiber was stretched or bent.

To bond the two materials together, the researchers added conjugation chemicals to the cladding solution, which, when coated over the hydrogel core, generated chemical links between the outer surfaces of both materials.

“It clicks together the carboxyl groups in the cladding, and the amine groups in the core material, like molecular-level glue,” Yuk says.

Sensing strain

The researchers tested the optical fibers’ ability to propagate light by shining a laser through fibers of various lengths. Each fiber transmitted light without significant attenuation, or fading. They also found that fibers could be stretched over seven times their original length without breaking.

Now that they had developed a highly flexible and robust optical fiber, made from a hydrogel material that was also biocompatible, the researchers began to play with the fiber’s optical properties, to see if they could design a fiber that could sense when and where it was being stretched.

They first loaded a fiber with red, green, and blue organic dyes, placed at specific spots along the fiber’s length. Next, they shone a laser through the fiber and stretched, for instance, the red region. They measured the spectrum of light that made it all the way through the fiber, and noted the intensity of the red light. They reasoned that this intensity relates directly to the amount of light absorbed by the red dye, as a result of that region being stretched.

In other words, by measuring the amount of light at the far end of the fiber, the researchers can quantitatively determine where and by how much a fiber was stretched.

“When you stretch a certain portion of the fiber, the dimensions of that part of the fiber changes, along with the amount of light that region absorbs and scatters, so in this way, the fiber can serve as a sensor of strain,” Liu explains.

“This is like a multistrain sensor through a single fiber,” Yuk adds. “So it can be an implantable or wearable strain gauge.”

The researchers imagine that such stretchable, strain-sensing optical fibers could be implanted or fitted along the length of a patient’s arm or leg, to monitor for signs of improving mobility.

Zhao envisions the fibers may also serve as sensors, lighting up in response to signs of disease.

“We may be able to use optical fibers for long-term diagnostics, to optically monitor tumors or inflammation,” he says. “The applications can be impactful.”

Here’s a link to and a citation for the paper,

Highly Stretchable, Strain Sensing Hydrogel Optical Fibers by Jingjing Guo, Xinyue Liu, Nan Jiang, Ali K. Yetisen, Hyunwoo Yuk, Changxi Yang, Ali Khademhosseini, Xuanhe Zhao, and Seok-Hyun Yun. Advanced Materials DOI: 10.1002/adma.201603160 Version of Record online: 7 OCT 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

New form of light could lead to circuits that run on photons instead of electrons

If circuits are running on photons instead of electrons, does that mean there will be no more electricity and electronics?  Apparently, the answer is not exactly. First, an Aug. 5, 2016 news item on ScienceDaily makes the announcement about photons and circuits,

New research suggests that it is possible to create a new form of light by binding light to a single electron, combining the properties of both.

According to the scientists behind the study, from Imperial College London, the coupled light and electron would have properties that could lead to circuits that work with packages of light — photons — instead of electrons.

It would also allow researchers to study quantum physical phenomena, which govern particles smaller than atoms, on a visible scale.

An Aug. 5, 2016 Imperial College of London (ICL) press release, which originated the news item, describes the research further (Note: A link has been removed),

In normal materials, light interacts with a whole host of electrons present on the surface and within the material. But by using theoretical physics to model the behaviour of light and a recently-discovered class of materials known as topological insulators, Imperial researchers have found that it could interact with just one electron on the surface.

This would create a coupling that merges some of the properties of the light and the electron. Normally, light travels in a straight line, but when bound to the electron it would instead follow its path, tracing the surface of the material.

Improved electronics

In the study, published today in Nature Communications, Dr Vincenzo Giannini and colleagues modelled this interaction around a nanoparticle – a small sphere below 0.00000001 metres in diameter – made of a topological insulator.

Their models showed that as well as the light taking the property of the electron and circulating the particle, the electron would also take on some of the properties of the light. [emphasis mine]

Normally, as electrons are travelling along materials, such as electrical circuits, they will stop when faced with a defect. However, Dr Giannini’s team discovered that even if there were imperfections in the surface of the nanoparticle, the electron would still be able to travel onwards with the aid of the light.

If this could be adapted into photonic circuits, they would be more robust and less vulnerable to disruption and physical imperfections.

Quantum experiments

Dr Giannini said: “The results of this research will have a huge impact on the way we conceive light. Topological insulators were only discovered in the last decade, but are already providing us with new phenomena to study and new ways to explore important concepts in physics.”

Dr Giannini added that it should be possible to observe the phenomena he has modelled in experiments using current technology, and the team is working with experimental physicists to make this a reality.

He believes that the process that leads to the creation of this new form of light could be scaled up so that the phenomena could observed much more easily.

Currently, quantum phenomena can only be seen when looking at very small objects or objects that have been super-cooled, but this could allow scientists to study these kinds of behaviour at room temperature.

An electron that takes on the properties of light? I find that fascinating.

Artistic image of light trapped on the surface of a nanoparticle topological insulator. Credit: Vincenzo Giannini

Artistic image of light trapped on the surface of a nanoparticle topological insulator. Credit: Vincenzo Giannini

For those who’d like more information, here’s a link to and a citation for the paper,

Single-electron induced surface plasmons on a topological nanoparticle by G. Siroki, D.K.K. Lee, P. D. Haynes,V. Giannini. Nature Communications 7, Article number: 12375  doi:10.1038/ncomms12375 Published 05 August 2016

This paper is open access.

Hologram with nanostructures could improve fraud protection

This research on holograms comes from Harvard University according to a May 13, 2016 news item on ScienceDaily,

Holograms are a ubiquitous part of our lives. They are in our wallets — protecting credit cards, cash and driver’s licenses from fraud — in grocery store scanners and biomedical devices.

Even though holographic technology has been around for decades, researchers still struggle to make compact holograms more efficient, complex and secure.

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences have programmed polarization into compact holograms. These holograms use nanostructures that are sensitive to polarization (the direction in which light vibrates) to produce different images depending on the polarization of incident light. This advancement, which works across the spectrum of light, improves anti-fraud holograms as well as those used in entertainment displays.

A May 13, 2016 Harvard University press release (also on EurekAlert) by Leah Burrows, which originated the news item, provides more detail,

“The novelty in this research is that by using nanotechnology, we’ve made holograms that are highly efficient, meaning that very little light is lost to create the image,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering and senior author of the paper. “By using incident polarized light, you can see far a crisper image and can store and retrieve more images. Polarization adds another dimension to holograms that can be used to protect against counterfeiting and in applications like displays.”

Harvard’s Office of Technology Development has filed patents on this and related technologies and is actively pursuing commercial opportunities.

Holograms, like digital photographs, capture a field of light around an object and encode it on a chip. However, photographs only record the intensity of light while holograms also capture the phase of light, which is why holograms appear three-dimensional.

“Our holograms work like any other but the image produced depends on the polarization state of the illuminating light, providing an extra degree of freedom in design for versatile applications,” said Mohammadreza Khorasaninejad, postdoctoral fellow in the Capasso Lab and first author of the paper.

There are several states of polarization. In linearly polarized light the direction of vibration remains constant while in circularly polarized light it rotates clockwise or counterclockwise. The direction of rotation is the chirality.

The team built silicon nanostructured patterns on a glass substrate, which act as superpixels. Each superpixel responds to a certain polarization state of the incident light. Even more information can be encoded in the hologram by designing and arranging the nanofins to respond differently to the chirality of the polarized incident light.

“Being able to encode chirality can have important applications in information security such as anti-counterfeiting,” said Antonio Ambrosio, a research scientist in the Capasso Lab and co-first author. “For example, chiral holograms can be made to display a sequence of certain images only when illuminated with light of specific polarization not known to the forger.”

“By using different nanofin designs in the future, one could store and retrieve far more images by employing light with many states of polarization,” said Capasso.

Because this system is compact, it has application in portable projectors, 3D movies and wearable optics.

“Modern polarization imaging systems require cascading several optical components such as beam splitters, polarizers and wave plates,” said Ambrosio. “Our metasurface can distinguish between incident polarization using a single layer dielectric surface.”

“We have also incorporated in some of the holograms a lens function that has allowed us to produce images at large angles,” said Khorasaninejad. “This functionality combined with the small footprint and lightweight, has significant potential for wearable optics applications.”

Here’s a link to and a citation for the paper,

Broadband and chiral binary dielectric meta-holograms by Mohammadreza Khorasaninejad, Antonio Ambrosio, Pritpal Kanhaiya, and Federico Capasso. Science Advances  13 May 2016: Vol. 2, no. 5, e1501258 DOI: 10.1126/sciadv.1501258

This paper is open access.

Explaining research into matching plasmonic nanoantenna resonances with atoms, molecules, and quantum dots

There’s a very nice explanation of the difficulties associeated with using plasmonic nanoantennas as sensors in a March 21, 2016 news item on phys.org,

Plasmonic nanoantennas are among the hot topics in science at the moment because of their ability to interact strongly with light, which for example makes them useful for different kinds of sensing. But matching their resonances with atoms, molecules or so called quantum dots has been difficult so far because of the very different length scales involved. Thanks to a grant from the Engkvist foundation, Timur Shegai, assistant professor at Chalmers University of Technology, hopes to find a way to do this and by that open doors for applications such as safe long distance communication channels.

A molecule being illuminated by two gold nanoantennas. By: Alexander Ericson Courtesy: Chalmers University of Technology

A molecule being illuminated by two gold nanoantennas. By: Alexander Ericson Courtesy: Chalmers University of Technology

The image, looking like a stylized butterfly or bow tie, above accompanies Karin Weijdegård’s March ??, 2016 Chalmers University of Technology press release, which originated the news item, expands on the research theme,

The diffraction limit makes it very hard for light to interact with the very smallest particles or so called quantum systems such as atoms, molecules or quantum dots. The size of such a particle is simply so much smaller than the wavelength of light that there cannot be a strong interaction between the two. But by using plasmonic nanoantennas, which can be described as metallic nanostructures that are able to focus light very strongly and in wavelengths smaller than those of the visible light, one can build a bridge between the light and the atom, molecule or quantum dot and that is what Timur Shegai is working on.

“Plasmonic nanostructures are themselves smaller than wavelengths of light, but because they have a lot of free electrons they can store the electromagnetic energy in a volume which is actually a lot smaller than the diffraction limit, which helps to bridge the gap between really small objects such as molecules and the larger wavelengths of light,” he says.

Matching the harmonic with the un-harmonic

This might sound easy enough, but the problem with combining the two is that they behave in very different ways. The behaviour of plasmonic nanostructures is very linear, like a harmonic oscillator it will regularly move from side to side no matter how much energy or in other words how many excitations are stored in it. On the other hand, so called quantum systems like atoms, molecules or quantum dots are very much the opposite – their optical properties are highly un-harmonic. Here it makes a big difference if you excite the system with one or two or hundreds of photons.

“Now imagine that you couple together this un-harmonic resonator and a harmonic resonator, and add the possibility to interact with light much stronger than the un-harmonic system alone would have allowed. That opens up very interesting possibilities for quantum technologies and for non-linear optics for example. But as opposed to previous attempts that have been done at very low temperatures and in a vacuum, we will do it at room temperature.”

Communication channels impossible to hack

One possible application where this technology could be useful in the future is to create channels for long distance communications that are impossible to hack. With the current technology this kind of safe communication is only possible if the persons communicating is within a distance of about one hundred kilometres from each other, because that is the maximum distance that an individual photon can run in fibres before it scatters and the signal is lost.

“The kind of ultra small and ultra fast technology we want to develop could be useful in a so called quantum repeater, a device that could be installed across the line from for example New York to London, that would repeat the photon every time it is about to be scattered,” says Timur Shegai.

At the moment though, it is the fundamental aspects of merging plasmons with quantum systems that interest Timur Shegai. To be able to experimentally prove that the there can be interactions between the two systems, he first of all needs to fabricate model systems at the nano level. This is a big challenge, but with the grant of 1,6 million SEK over a period of two years that he just received from the Engkvist foundation, the chances of success have improved.

“Since I am a researcher at the beginning of my career every person is a huge improvement and now I can hire a post doc to work with my group. This means that the project can be divided into sub parts and together we will be able to explore more possibilities about this new technology.”

Thank you Karin Weijdegård for the explanation.

Australians take step toward ‘smart’ contact lenses

Some research from RMIT University (Australia) and the University of Adelaide (Australia) is make quite an impression. A Feb. 19, 2016 article by Caleb Radford for The Lead explains some of the excitement,

NEW light-manipulating nano-technology may soon be used to make smart contact lenses.

The University of Adelaide in South Australia worked closely with RMIT University to develop small hi-tech lenses to filter harmful optical radiation without distorting vision.

Dr Withawat Withayachumnankul from the University of Adelaide helped conceive the idea and said the potential applications of the technology included creating new high-performance devices that connect to the Internet.

A Feb. 19, 2016 RMIT University press release on EurekAlert, which originated the news item, provides more detail,

The light manipulation relies on creating tiny artificial crystals termed “dielectric resonators”, which are a fraction of the wavelength of light – 100-200 nanometers, or over 500 times thinner than a human hair.

The research combined the University of Adelaide researchers’ expertise in interaction of light with artificial materials with the materials science and nanofabrication expertise at RMIT University.

Dr Withawat Withayachumnankul, from the University of Adelaide’s School of Electrical and Electronic Engineering, said: “Manipulation of light using these artificial crystals uses precise engineering.

“With advanced techniques to control the properties of surfaces, we can dynamically control their filter properties, which allow us to potentially create devices for high data-rate optical communication or smart contact lenses.

“The current challenge is that dielectric resonators only work for specific colours, but with our flexible surface we can adjust the operation range simply by stretching it.”

Associate Professor Madhu Bhaskaran, Co-Leader of the Functional Materials and Microsystems Research Group at RMIT, said the devices were made on a rubber-like material used for contact lenses.

“We embed precisely-controlled crystals of titanium oxide, a material that is usually found in sunscreen, in these soft and pliable materials,” she said.

“Both materials are proven to be bio-compatible, forming an ideal platform for wearable optical devices.

“By engineering the shape of these common materials, we can create a device that changes properties when stretched. This modifies the way the light interacts with and travels through the device, which holds promise of making smart contact lenses and stretchable colour changing surfaces.”

Lead author and RMIT researcher Dr. Philipp Gutruf said the major scientific hurdle overcome by the team was combining high temperature processed titanium dioxide with the rubber-like material, and achieving nanoscale features.

“With this technology, we now have the ability to develop light weight wearable optical components which also allow for the creation of futuristic devices such as smart contact lenses or flexible ultra thin smartphone cameras,” Gutruf said.

Here’s a link to and a citation for the paper,

Mechanically Tunable Dielectric Resonator Metasurfaces at Visible Frequencies by Philipp Gutruf, Chengjun Zou, Withawat Withayachumnankul, Madhu Bhaskaran, Sharath Sriram, and Christophe Fumeaux. ACS Nano, 2016, 10 (1), pp 133–141 DOI: 10.1021/acsnano.5b05954 Publication Date (Web): November 30, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

ETA Feb. 24, 2016: Dexter Johnson (Nanoclast blog on the IEEE [Institute of Electrical and Electronics Engineers] website) has chimed in with additional insight into this research in his Feb. 23, 2016 posting.

Quantum and classical physics may be closer than we thought

It seems that a key theory about the boundary between the quantum world and our own macro world has been disproved and I think the July 21, 2015 news item on Nanotechnology Now says it better,

Quantum theory is one of the great achievements of 20th century science, yet physicists have struggled to find a clear boundary between our everyday world and what Albert Einstein called the “spooky” features of the quantum world, including cats that could be both alive and dead, and photons that can communicate with each other across space instantaneously.

For the past 60 years, the best guide to that boundary has been a theorem called Bell’s Inequality, but now a new paper shows that Bell’s Inequality is not the guidepost it was believed to be, which means that as the world of quantum computing brings quantum strangeness closer to our daily lives, we understand the frontiers of that world less well than scientists have thought.

In the new paper, published in the July 20 [2015] edition of Optica, University of Rochester [New York state, US] researchers show that a classical beam of light that would be expected to obey Bell’s Inequality can fail this test in the lab, if the beam is properly prepared to have a particular feature: entanglement.

A July 21, 2015 University of Rochester news release, which originated the news item, reveals more about the boundary and the research,

Not only does Bell’s test not serve to define the boundary, the new findings don’t push the boundary deeper into the quantum realm but do just the opposite. They show that some features of the real world must share a key ingredient of the quantum domain. This key ingredient is called entanglement, exactly the feature of quantum physics that Einstein labeled as spooky. According to Joseph Eberly, professor of physics and one of the paper’s authors, it now appears that Bell’s test only distinguishes those systems that are entangled from those that are not. It does not distinguish whether they are “classical” or quantum. In the forthcoming paper the Rochester researchers explain how entanglement can be found in something as ordinary as a beam of light.

Eberly explained that “it takes two to tangle.” For example, think about two hands clapping regularly. What you can be sure of is that when the right hand is moving to the right, the left hand is moving to the left, and vice versa. But if you were asked to guess without listening or looking whether at some moment the right hand was moving to the right, or maybe to the left, you wouldn’t know. But you would still know that whatever the right hand was doing at that time, the left hand would be doing the opposite. The ability to know for sure about a common property without knowing anything for sure about an individual property is the essence of perfect entanglement.

Eberly added that many think of entanglement as a quantum feature because “Schrodinger coined the term ‘entanglement’ to refer to his famous cat scenario.” But their experiment shows that some features of the “real” world must share a key ingredient of Schrodinger’s Cat domain: entanglement.

The existence of classical entanglement was pointed out in 1980, but Eberly explained that it didn’t seem a very interesting concept, so it wasn’t fully explored. As opposed to quantum entanglement, classical entanglement happens within one system. The effect is all local: there is no action at a distance, none of the “spookiness.”

With this result, Eberly and his colleagues have shown experimentally “that the border is not where it’s usually thought to be, and moreover that Bell’s Inequalities should no longer be used to define the boundary.”

Here’s a link to and a citation for the paper,

Shifting the quantum-classical boundary: theory and experiment for statistically classical optical fields by Xiao-Feng Qian, Bethany Little, John C. Howell, and J. H. Eberly. Optica Vol. 2, Issue 7, pp. 611-615 (2015) •doi: 10.1364/OPTICA.2.000611

This paper is open access.

Unique ‘printing’ process boosts supercapacitor performance

In addition to creating energy, we also need to store some of it for future use as a July 29, 2013 news release from the University of Central Florida notes,

Researchers at the University of Central Florida have developed a technique to increase the energy storage capabilities of supercapacitors, essential devices for powering high-speed trains, electric cars, and the emergency doors of the Airbus A380.

The finding, which offers a solution to a problem that has plagued the growing multi-billion dollar industry, utilizes a unique three-step process to “print” large – area nanostructured electrodes, structures necessary to improve electrical conductivity and boost performance of the supercapacitor.

Jayan Thomas, an assistant professor in UCF’s NanoScience Technology Center, led the project which is featured in the June edition of Advanced Materials, one of the leading peer-reviewed scientific journals covering materials science in the world. Thomas’ research appears on the journal’s highly-coveted frontispiece, the illustration page of the journal that precedes the title page.

The news release goes on to describe the supercapacitor issue the researchers were addressing,

Supercapacitors have been around since the 1960’s. Similar to batteries, they store energy. The difference is that supercapacitors can provide higher amounts of power for shorter periods of time, making them very useful for heavy machinery and other applications that require large amounts of energy to start.  However, due to their innate low energy density; supercapacitors are limited in the amount of energy that they can store.

“We had been looking at techniques to print nanostructures,” said Thomas. “Using a simple spin-on nanoprinting (SNAP) technique, we can print highly-ordered nanopillars without the need for complicated development processes. By eliminating these processes, it allows multiple imprints to be made on the same substrate in close proximity.“

This simplified fabrication method devised by Thomas and his team is very attractive for the next-generation of energy storage systems. “What we’ve found is by adding the printed ordered nanostructures to supercapacitor electrodes, we can increase their surface area many times,” added Thomas. “We discovered that supercapacitors made using the SNAP technique can store much more energy than ones made without.”

Here’s a link to and a citation for the research paper abut this new technique for supercapacitors,

Energy Storage: Highly Ordered MnO2 Nanopillars for Enhanced Supercapacitor Performance (Adv. Mater. 24/2013) by Zenan Yu, Binh Duong, Danielle Abbitt, and Jayan Thomas. Article first published online: 20 JUN 2013 DOI: 10.1002/adma.201370160 Advanced Materials Volume 25, Issue 24, page 3301, June 25, 2013.

Lead researcher Thomas was recently featured in a video for his work on creating plasmonic nanocrystals from gold nanoparticles (from the news release),

Thomas, who is also affiliated with the College of Optics and Photonics (CREOL), and the College of Engineering, was recently featured on American Institute of Physics’ Inside Science TV for his collaborative research to develop a new material using nanotechnology that could potentially help keep pilots safe by diffusing harmful laser light.

Here’s the video,

You can find videos, news, and blogs featuring other research at Inside Science and you can find out more about Dr. Jayan Thomas here.