Tag Archives: photonics

Noniridescent photonics inspired by tarantulas

Last year, I was quite taken with a structural colour story centering on tarantulas which was featured in my Dec. 7, 2015 posting.

Cobalt Blue Tarantula [downloaded from http://www.tarantulaguide.com/tarantula-pictures/cobalt-blue-tarantula-4/]

Cobalt Blue Tarantula [downloaded from http://www.tarantulaguide.com/tarantula-pictures/cobalt-blue-tarantula-4/]

On Oct. 17, 2016 I was delighted to receive an email with the latest work from the same team who this time around crowdfunded resources to complete their research. Before moving on to the paper, here’s more from the team’s crowdfunder on Experiment was titled “The Development of Non-iridescent Structurally Colored Material Inspired by Tarantula Hairs,”

Many vibrant colors in nature are produced by nanostructures rather than pigments. But their application is limited by iridescence – changing hue and brightness with viewing angles. This project aims to mimic the nanostructures that tarantulas use to produce bright, non-iridescent blue colors to inspire next-generation, energy efficient, wide-angle color displays. Moreover, one day non-iridescent structural colorants may replace costly and toxic pigments and dyes.

What is the context of this research?

We recently discovered that some tarantulas produce vivid blue colors using unique nanostructures not found in other blue organisms like birds and Morpho butterflies. We described a number of different nanostructures that help explain how blue color evolved at least eight times within tarantulas. These colors are also remarkably non-iridescent so that they stay bright blue even at wide viewing angles, unlike the “flashy” structural colors seen in many birds and butterflies. We hypothesize that although the hue is produced by multilayer nanostructure, it is the hierarchical morphology of the hairs controls iridescence. We would like to validate our results from preliminary optical simulations by making nano-3D printed physical prototypes with and without key features of the tarantula hairs.

What is the significance of this project?

While iridescence can make a flashy signal to a mating bird or butterfly, it isn’t so useful in optical technology. This limits the application of structural colors in human contexts, even though they can be more vibrant and resist fading better than traditional pigment-based colors. For example, despite being energy efficient and viewable in direct sunlight, this butterfly-inspired color display, that utilizes principles of structural colors, has never made it into the mainstream because iridescence limits its viewing angle. We believe this limitation could be overcome using tarantula-inspired nanostructures that could be mass-produced in an economically viable way through top-down approaches. Those nanostructures may even be used to replace pigments and dyes someday!

What are the goals of the project?

We have designed five models that vary in complexity, incorporating successively more details of real tarantula hairs. We would like to fabricate those five designs by 3D nano-printing, so that we can test our hypothesis experimentally and determine which features produce blue and which remove iridescence. We’ll start making those designs as soon as we reach our goal and the project is fully funded. Once these designs are made, we will compare the angle-dependency of the colors produced by each design through angle-resolved reflectance spectrometry. We’ll also compare them visually through photography by taking series of shots from different angles similar to Fig. S4. Through those steps, we’ll be able to identify how each feature of the complex nanostructure contributes to color.

Ultra-high resolution (nano-scale) 3D printing
To fund nano 3D printing completely

This project has been designed using Biomimicry Thinking, and is a follow-up to our published, well-received tarantula research. In order to test our hypothesis, we are planning to use Photonic Professional GT by nanoscribe to fabricate tarantula hair-inspired prototypes by 3D printing nanostructures within millimeter sized swatches. To be able to 3D print nanostructures across these relatively large-sized swatches is critical to the success of our project. Currently, there’s no widely-accessible technology out there that meets our needs other than Photonic Professional GT. However, the estimated cost just for 3D printing those nanostructures alone is $20,000. So far, we have successfully raised and allocated $13,000 of research funds through conventional means, but we are still $7,000 short. Initial trial of our most complex prototype was a success. Therefore, we’re here, seeking your help. Please help us make this nano fabrication happen, and make this project a success! Thank you!

The researchers managed to raise $7, 708.00 in total, making this paper possible,

Tarantula-Inspired Noniridescent Photonics with Long-Range Order by Bor-Kai Hsiung, Radwanul Hasan Siddique, Lijia Jiang, Ying Liu, Yongfeng Lu, Matthew D. Shawkey, and Todd A. Blackledge. Advanced Materials DOI: 10.1002/adom.201600599 Version of Record online: 11 OCT 2016

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

This paper is behind a paywall but I did manage to get my hands on a copy. So here are a few highlights from the paper,

Pigment-based colorants are used for applications ranging from textiles to packaging to cosmetics.[1] However, structural-based alternatives can be more vibrant, durable, and eco-friendly relative to pigmentary colors.[2] Moreover, optical nanostructures are highly tunable, they can achieve a full color gamut by slight alterations to spacing.[3] However, light interference and/or diffraction from most photonic structures results in iridescence,[4] which limits their broader applications. Iridescent colors that change hue when viewed from different directions are useful for niche markets, such as security and anticounterfeiting, {emphasis mine} [5] but are not desirable for most applications, such as paints, coatings, electronic displays, and apparels. Hence, fabricating a photonic structure that minimizes iridescence is a key step to unlocking the potential applications of structural colors.

Noniridescent structural colors in nature are produced by coherent scattering of light by quasi-ordered, amorphous photonic structures (i.e., photonic glass),[6–10] or photonic polycrystals [9,11–14] that possess only short-range order. Iridescence is thought to be a fundamental component of photonic structures with long-range order, such as multilayers.[4] However, the complexity of short-range order photonic structures prohibits their design and fabrication using top-down approaches while bottom-up synthesis using colloidal suspension[15,16] or self-assembly[17–20] lack the tight controls over the spatial and temporal scales needed for industrial mass production. Photonic structures with long-range order are easier to model mathematically. Hence, long-range order photonic structures are intrinsically suitable for top-down fabrication, where precise feature placement and scalability can be guaranteed.

Recently, we found blue color produced by multilayer interference on specialized hairs from two species of blue tarantulas (Poecilotheria metallica (Figure 1a,b) and Lampropelma violaceopes) that was largely angle independent.[21] We hypothesize that the iridescent effects of the multilayer are reduced by hierarchical structuring of the hairs. Specifically, the hairs have: (1) high degrees of rotational symmetry, (2) hierarchy—with subcylindrical multilayers surrounding a larger, overarching multilayer cylinder, and (3) nanoscale surface grooves. Because all of these structures co-occur on the tarantulas, it is impossible to decouple them simply by observing nature. Here, we use optical simulation and nano-3D rapid prototyping to demonstrate that introducing design features seen in these tarantulas onto a multilayer photonic structure nearly eliminates iridescence. As far as we are aware, this is the first known example of a noniridescent structural color produced by a photonic structure with both short and long-range order. This opens up an array of new possibilities for photonic structure design and fabrication to produce noniridescent structural colors and is a key first step to achieving economically viable solutions for mass production of noniridescent structural color.  … (p. 1 PDF)

There is a Canadian security and anti-counterfeiting company (Nanotech Security Corp.), inspired by the Morpho butterfly and its iridescent blue, which got its start in Bozena Kaminska’s laboratory at Simon Fraser University (Vancouver, Canada).

Getting back to the paper, after a few twists and turns, they conclude with this,

This approach of producing noniridescent structural colors using photonic structures with long-range order (i.e., modified multilayer) has, to our knowledge, not been explored previously. Our findings reaffirm the value of using nature and the biomimetic process as a tool for innovation and our approach also may help to overcome the current inability of colloidal self-assembly to achieve pure noniridescent structural red due to single-particle scattering and/or multiple scattering.[25] As a result, our research provides a new and easy way for designing structural colorants with customizable hues (see Figure S6, Supporting Information, as one of the potential examples) and iridescent effects to satisfy the needs of different applications. While nano-3D printing of these nanostructures is not viable for mass production, it does identify the key features that are necessary for top-down fabrication. With promising nanofabrication techniques, such as preform drawing[26]—a generally scalable methodology that has been demonstrated for fabricating particles with complex internal architectures and continuously tunable diameters down to nanometer scale[27] – it is possible to mass produce these “designer structural colorants” in an economically viable manner. Our discovery of how to produce noniridescent structural colors using long-range order may therefore lead to a more sustainable future that does not rely upon toxic and wasteful synthetic pigments and dyes. (p. 5)

I’m glad to have gotten caught up with the work. Thank you, Bor-Kai Hsiung.

Phenomen: a future and emerging information technology project

A Sept. 19, 2016 news item on Nanowerk describes a new research project incorporating photonics, phononics, and radio frequency signal processing,

HENOMEN is a ground breaking project designed to harness the potential of combined phononics, photonics and radio-frequency (RF) electronic signals to lay the foundations of a new information technology. This new Project, funded though the highly competitive H2020 [the European Union’s Horizon 2020 science funding programme] FET [Future and Emerging Technologies]-Open call, joins the efforts of three leading research institutes, three internationally recognised universities and a high-tech SME. The Consortium members kick-offed the project with a meeting on Friday September 16, 2016, at the Catalan Institute of Nanoscience and Nanotechnology (ICN2), coordinated by ICREA Research Prof Dr Clivia M. Sotomayor-Torres, of the ICN2’ Phononic and Photonic Nanostructures (P2N) Group.

A Sept. 16, 2016 ICN2 press release, which originated the news item, provides more detail,

Most information is currently transported by electrical charge (electrons) and by light (photons). Phonons are the quanta of lattice vibrations with frequencies covering a wide range up to tens of THz and provide coupling to the surrounding environment. In PHENOMEN the core of the research will be focused on phonon-based signal processing to enable on-chip synchronisation and transfer information carried between optical channels by phonons.

This ambitious prospect could serve as a future scalable platform for, e.g., hybrid information processing with phonons. To achieve it, PHENOMEN proposes to build the first practical optically-driven phonon sources and detectors including the engineering of phonon lasers to deliver coherent phonons to the rest of the chip pumped by a continuous wave optical source. It brings together interdisciplinary scientific and technology oriented partners in an early-stage research towards the development of a radically new technology.

The experimental implementation of phonons as information carriers in a chip is completely novel and of a clear foundational character. It deals with interaction and manipulation of fundamental particles and their intrinsic dual wave-particle character. Thus, it can only be possible with the participation of an interdisciplinary consortium which will create knowledge in a synergetic fashion and add value in the form of new theoretical tools,  develop novel methods to manipulate coherent phonons with light and build all-optical phononic circuits enabled by optomechanics.

The H2020 FET-Open call “Novel ideas for radically new technologies” aims to support the early stages of joint science and technology research for radically new future technological possibilities. The call is entirely non-prescriptive with regards to the nature or purpose of the technologies that are envisaged and thus targets mainly the unexpected. PHENOMEN is one of the 13 funded Research & Innovation Actions and went through a selection process with a success rate (1.4%) ten times smaller than that for an ERC grant. The retained proposals are expected to foster international collaboration in a multitude of disciplines such as robotics, nanotechnology, neuroscience, information science, biology, artificial intelligence or chemistry.

The Consortium

The PHENOMEN Consortium is made up by:

  • 3 leading research institutes:
  • 3 universities with an internationally recognised track-record in their respective areas of expertise:
  • 1 industrial partner:

Replicating brain’s neural networks with 3D nanoprinting

An announcement about European Union funding for a project to reproduce neural networks by 3D nanoprinting can be found in a June 10, 2016 news item on Nanowerk,

The MESO-BRAIN consortium has received a prestigious award of €3.3million in funding from the European Commission as part of its Future and Emerging Technology (FET) scheme. The project aims to develop three-dimensional (3D) human neural networks with specific biological architecture, and the inherent ability to interrogate the network’s brain-like activity both electrophysiologically and optically. It is expected that the MESO-BRAIN will facilitate a better understanding of human disease progression, neuronal growth and enable the development of large-scale human cell-based assays to test the modulatory effects of pharmacological and toxicological compounds on neural network activity. The use of more physiologically relevant human models will increase drug screening efficiency and reduce the need for animal testing.

A June 9, 2016 Institute of Photonic Sciences (ICFO) press release (also on EurekAlert), which originated the news item, provides more detail,

About the MESO-BRAIN project

The MESO-BRAIN project’s cornerstone will use human induced pluripotent stem cells (iPSCs) that have been differentiated into neurons upon a defined and reproducible 3D scaffold to support the development of human neural networks that emulate brain activity. The structure will be based on a brain cortical module and will be unique in that it will be designed and produced using nanoscale 3D-laser-printed structures incorporating nano-electrodes to enable downstream electrophysiological analysis of neural network function. Optical analysis will be conducted using cutting-edge light sheet-based, fast volumetric imaging technology to enable cellular resolution throughout the 3D network. The MESO-BRAIN project will allow for a comprehensive and detailed investigation of neural network development in health and disease.

Prof Edik Rafailov, Head of the MESO-BRAIN project (Aston University) said: “What we’re proposing to achieve with this project has, until recently, been the stuff of science fiction. Being able to extract and replicate neural networks from the brain through 3D nanoprinting promises to change this. The MESO-BRAIN project has the potential to revolutionise the way we are able to understand the onset and development of disease and discover treatments for those with dementia or brain injuries. We cannot wait to get started!”

The MESO-BRAIN project will launch in September 2016 and research will be conducted over three years.

About the MESO-BRAIN consortium

Each of the consortium partners have been chosen for the highly specific skills & knowledge that they bring to this project. These include technologies and expertise in stem cells, photonics, physics, 3D nanoprinting, electrophysiology, molecular biology, imaging and commercialisation.

Aston University (UK) Aston Institute of Photonic Technologies (School of Engineering and Applied Science) is one of the largest photonic groups in UK and an internationally recognised research centre in the fields of lasers, fibre-optics, high-speed optical communications, nonlinear and biomedical photonics. The Cell & Tissue Biomedical Research Group (Aston Research Centre for Healthy Ageing) combines collective expertise in genetic manipulation, tissue engineering and neuronal modelling with the electrophysiological and optical analysis of human iPSC-derived neural networks. Axol Bioscience Ltd. (UK) was founded to fulfil the unmet demand for high quality, clinically relevant human iPSC-derived cells for use in biomedical research and drug discovery. The Laser Zentrum Hannover (Germany) is a leading research organisation in the fields of laser development, material processing, laser medicine, and laser-based nanotechnologies. The Neurophysics Group (Physics Department) at University of Barcelona (Spain) are experts in combing experiments with theoretical and computational modelling to infer functional connectivity in neuronal circuits. The Institute of Photonic Sciences (ICFO) (Spain) is a world-leading research centre in photonics with expertise in several microscopy techniques including light sheet imaging. KITE Innovation (UK) helps to bridge the gap between the academic and business sectors in supporting collaboration, enterprise, and knowledge-based business development.

For anyone curious about the FET funding scheme, there’s this from the press release,

Horizon 2020 aims to ensure Europe produces world-class science by removing barriers to innovation through funding programmes such as the FET. The FET (Open) funds forward-looking collaborations between advanced multidisciplinary science and cutting-edge engineering for radically new future technologies. The published success rate is below 1.4%, making it amongst the toughest in the Horizon 2020 suite of funding schemes. The MESO-BRAIN proposal scored a perfect 5/5.

You can find out more about the MESO-BRAIN project on its ICFO webpage.

They don’t say anything about it but I can’t help wondering if the scientists aren’t also considering the possibility of creating an artificial brain.

5D data storage is forever

Combine nanostructured glass and femtosecond laser writing with five-dimensional digital data and you can wave goodbye to any anxieties about losing information. Researchers at Southampton University (UK) made the announcement in a Feb. 15, 2016 news item on ScienceDaily,

Scientists at the University of Southampton have made a major step forward in the development of digital data storage that is capable of surviving for billions of years.

Using nanostructured glass, scientists from the University’s Optoelectronics Research Centre (ORC) have developed the recording and retrieval processes of five dimensional (5D) digital data by femtosecond laser writing.

A Feb. 15, 2016 University of Southampton press release (also on EurekAlert), which originated the news item, offers more detail,

The storage allows unprecedented properties including 360 TB [Terabyte]/disc data capacity, thermal stability up to 1,000°C and virtually unlimited lifetime at room temperature (13.8 billion years at 190°C ) opening a new era of eternal data archiving. As a very stable and safe form of portable memory, the technology could be highly useful for organisations with big archives, such as national archives, museums and libraries, to preserve their information and records.

The technology was first experimentally demonstrated in 2013 when a 300 kb [kilobit] digital copy of a text file was successfully recorded in 5D.

Now, major documents from human history such as [the] Universal Declaration of Human Rights (UDHR), Newton’s Opticks, Magna Carta and Kings [sic] James Bible, have been saved as digital copies that could survive the human race. A copy of the UDHR encoded to 5D data storage was recently presented to UNESCO by the ORC at the International Year of Light (IYL) closing ceremony in Mexico.

The documents were recorded using ultrafast laser, producing extremely short and intense pulses of light. The file is written in three layers of nanostructured dots separated by five micrometres (one millionth of a metre).

The self-assembled nanostructures change the way light travels through glass, modifying polarisation of light that can then be read by combination of optical microscope and a polariser, similar to that found in Polaroid sunglasses.

Coined as the ‘Superman memory crystal’, as the glass memory has been compared to the “memory crystals” used in the Superman films, the data is recorded via self-assembled nanostructures created in fused quartz. The information encoding is realised in five dimensions: the size and orientation in addition to the three dimensional position of these nanostructures.

Professor Peter Kazansky, from the ORC, says: “It is thrilling to think that we have created the technology to preserve documents and information and store it in space for future generations. This technology can secure the last evidence of our civilisation: all we’ve learnt will not be forgotten.”

The researchers will present their research at the photonics industry’s renowned SPIE—The International Society for Optical Engineering Conference in San Francisco, USA this week. The invited paper, ‘5D Data Storage by Ultrafast Laser Writing in Glass’ will be presented on Wednesday 17 February [2016].

The team are now looking for industry partners to further develop and commercialise this ground-breaking new technology.

I have written a number of pieces about digitization, data storage, and memory such as this Jan. 30, 2014 post titled, Does digitizing material mean it’s safe? A tale of Canada’s Fisheries and Oceans scientific libraries. If you scroll down about 50% of the way, you’ll find some material that provides an overview.

Universal Declaration of Human Rights recorded into 5D optical data

Universal Declaration of Human Rights recorded into 5D optical data


Getting back to incandescent light (recycling the military way)

MIT (Massachusetts Institute of Technology) issued two news releases about this research into reclaiming incandescent light or as they call it “recycling light.” First off, there’s the Jan. 11, 2016 MIT Institute of Soldier Nanotechnologies news release by Paola Rebusco on EurekAlert,

Humanity started recycling relatively early in its evolution: there are proofs that trash recycling was taking place as early as in the 500 BC. What about light recycling? Consider light bulbs: more than one hundred and thirty years ago Thomas Edison patented the first commercially viable incandescent light bulb, so that “none but the extravagant” would ever “burn tallow candles”, paving the way for more than a century of incandescent lighting. In fact, emergence of electric lighting was the main motivating factor for deployment of electricity into every home in the world. The incandescent bulb is an example of a high temperature thermal emitter. It is very useful, but only a small fraction of the emitted light (and therefore energy) is used: most of the light is emitted in the infrared, invisible to the human eye, and in this context wasted.

Now, in a study published in Nature Nanotechnology on January 11th 2016 (online), a team of MIT researchers describes another way to recycle light emitted at unwanted infrared wavelengths while optimizing the emission at useful visible wavelengths. …

“For a thermal emitter at moderate temperatures one usually nano-patterns its surface to alter the emission,” says Ilic [postdoc Ognjen Ilic], the lead author of the study. “At high temperatures” – a light bulb filament reaches 3000K! – “such nanostructures deteriorate and it is impossible to alter the emission spectrum by having a nanostructure directly on the surface of the emitter.” The team solved the problem by surrounding the hot object with special nanophotonic structures that spectrally filter the emitted light, meaning that they let the light reflect or pass through based on its color (i.e. its wavelength). Because the filters are not in direct physical contact with the emitter, temperatures can be very high.

To showcase this idea, the team picked one of the highest temperature thermal emitters available – an incandescent light bulb. The authors designed nanofilters to recycle the infrared light, while allowing the visible light to go through. “The key advance was to design a photonic structure that transmits visible light and reflects infrared light for a very wide range of angles,” explains Ilic. “Conventional photonic filters usually operate for a single incidence angle. The challenge for us was to extend the desired optical properties across all directions,” a feat the authors achieved using special numerical optimization techniques.

However, for this scheme to work, the authors had to redesign the incandescent filament from scratch. “In a regular light bulb, the filament is a long and curly piece of tungsten wire. Here, the filament is laser-machined out of a flat sheet of tungsten: it is completely planar,” says Bermel [professor Peter Bermel now at Purdue University]. A planar filament has a large area, and is therefore very efficient in re-absorbing the light that was reflected by the filter. In describing how the new device differs from previously suggested concepts, Soljačić [professor Marin Soljačić], the project lead, emphasizes that “it is the combination of the exceptional properties of the filter and the shape of the filament that enabled substantial recycling of unwanted radiated light.”

In the new-concept light bulb prototype built by the authors, the efficiency approaches some fluorescent and LED bulbs. Nonetheless, the theoretical model predicts plenty of room for improvement. “This experimental device is a proof-of-concept, at the low end of performance that could be ultimately achieved by this approach,” argues Celanovic [principal research scientist Ivan Celanovic]. There are other advantages of this approach: “An important feature is that our demonstrated device achieves near-ideal rendering of colors,” notes Ilic, referring to the requirement of light sources to faithfully reproduce surrounding colors. That is precisely the reason why incandescent lights remained dominant for so long: their warm light has remained preferable to drab fluorescent lighting for decades.

Some practical questions need to be addressed before this technology can be widely adopted. “We will work closely with our mechanical engineering colleagues at MIT to try to tackle the issues of thermal stability and long-lifetime,” says Soljačić. The authors are particularly excited about the potential for producing these devices cheaply. “The materials we need are abundant and inexpensive,” Joannopoulos [professor John Joannopoulos] notes, “and the filters themselves–consisting of stacks of commonly deposited materials–are amenable to large-scale deposition.”

Chen [professor Gang Chen] comments further: “The lighting potential of this technology is exciting, but the same approach could also be used to improve the performance of energy conversion schemes such as thermo-photovoltaics.” In a thermo-photovoltaic device, external heat causes the material to glow, emitting light that is converted into an electric current by an absorbing photovoltaic element.

The last point captures the main motivation behind the work. “Light radiated from a hot object can be quite useful, whether that object is an incandescent filament or the Sun,” Ilic says. At its core, this work is about recycling thermal light for a specific application; “a 3000-degree filament is one of the hottest and the most challenging sources to work with,” Ilic continues. “It’s also what makes it a crucial test of our approach.”

There are a few more details in the 2nd Jan. 11, 2016 MIT news release on EurekAlert,

Light recycling

The key is to create a two-stage process, the researchers report. The first stage involves a conventional heated metal filament, with all its attendant losses. But instead of allowing the waste heat to dissipate in the form of infrared radiation, secondary structures surrounding the filament capture this radiation and reflect it back to the filament to be re-absorbed and re-emitted as visible light. These structures, a form of photonic crystal, are made of Earth-abundant elements and can be made using conventional material-deposition technology.

That second step makes a dramatic difference in how efficiently the system converts light into electricity. The efficiency of conventional incandescent lights is between 2 and 3 percent, while that of fluorescents (including CFLs) is currently between 7 and 13 percent, and that of LEDs between 5 and 13 percent. In contrast, the new two-stage incandescents could reach efficiencies as high as 40 percent, the team says.

The first proof-of-concept units made by the team do not yet reach that level, achieving about 6.6 percent efficiency. But even that preliminary result matches the efficiency of some of today’s CFLs and LEDs, they point out. And it is already a threefold improvement over the efficiency of today’s incandescents.

The team refers to their approach as “light recycling,” says Ilic, since their material takes in the unwanted, useless wavelengths of energy and converts them into the visible light wavelengths that are desired. “It recycles the energy that would otherwise be wasted,” says Soljačić.

Bulbs and beyond

One key to their success was designing a photonic crystal that works for a very wide range of wavelengths and angles. The photonic crystal itself is made as a stack of thin layers, deposited on a substrate. “When you put together layers, with the right thicknesses and sequence,” Ilic explains, you can get very efficient tuning of how the material interacts with light. In their system, the desired visible wavelengths pass right through the material and on out of the bulb, but the infrared wavelengths get reflected as if from a mirror. They then travel back to the filament, adding more heat that then gets converted to more light. Since only the visible ever gets out, the heat just keeps bouncing back in toward the filament until it finally ends up as visible light.

I appreciate both MIT news release writers for “Thomas Edison patented the first commercially viable incandescent light bulb” (Rebusco) and the unidentified writer of the 2nd MIT news release for this, from the news release, “Incandescent bulbs, commercially developed by Thomas Edison (and still used by cartoonists as the symbol of inventive insight) … .” Edison did not invent the light bulb. BTW, the emphases are mine.

For interested parties, here’s a link to and a citation for the paper,

Tailoring high-temperature radiation and the resurrection of the incandescent source by Ognjen Ilic, Peter Bermel, Gang Chen, John D. Joannopoulos, Ivan Celanovic, & Marin Soljačić. Nature Nanotechnology  (2016) doi:10.1038/nnano.2015.309 Published online 11 January 2016

This paper is behind a paywall.

Building architecture inspires new light-bending material

Usually, it’s nature which inspires scientists but not this time. Instead, a building in Canberra, Australia has provided the inspiration according to a March 24, 2015 news item on Nanowerk,

Physicists inspired by the radical shape of a Canberra building have created a new type of material which enables scientists to put a perfect bend in light.

The creation of a so-called topological insulator could transform the telecommunications industry’s drive to build an improved computer chip using light.

Leader of the team, Professor Yuri Kivshar from The Australian National University (ANU) said the revolutionary material might also be useful in microscopes, antenna design, and even quantum computers.

“There has been a hunt for similar materials in photonics based on large complicated structures,” said Professor Kivshar, who is the head of the Nonlinear Physics Centre in ANU Research School of Physics and Engineering.

“Instead we used a simple, small-scale zigzag structure to create a prototype of these novel materials with amazing properties.”

The structure was inspired by the Nishi building near ANU, which consists of rows of offset zigzag walls.

Here’s what the building looks like,

Caption: Alex Slobozhanyuk (L) and Andrey Miroshnichenko with models of their material structures in front of the Nishi building that inspired them. Credit: Stuart Hay, ANU

Caption: Alex Slobozhanyuk (L) and Andrey Miroshnichenko with models of their material structures in front of the Nishi building that inspired them.
Credit: Stuart Hay, ANU

A March 24, 2015 Australian National University press release, which originated the news item, goes on to describe topological insulators and what makes this ‘zigzag’ approach so exciting,

Topological insulators have been initially developed for electronics, and the possibility of building an optical counterpart is attracting a lot of attention.

The original zigzag structure of the material was suggested in the team’s earlier collaboration with Dr Alexander Poddubny, from Ioffe Institute in Russia, said PhD student Alexey Slobozhanyuk.

“The zigzag structure creates a coupling throughout the material that prevents light from travelling through its centre,” Mr Slobozhanyuk said.

“Instead light is channelled to the edges of the material, where it becomes completely localised by means of a kind of quantum entanglement known as topological order.”

Fellow researcher Dr Andrew Miroshnichenko said the building inspired the researchers to think of multiple zigzags.

“We had been searching for a new topology and one day I looked at the building and a bell went off in my brain,” said fellow researcher Dr Andrey Miroshnichenko.

“On the edges of such a material the light should travel completely unhindered, surfing around irregularities that would normally scatter the light.

“These materials will allow light to be bent around corners with no loss of signal,” he said.

The team showed that the exceptional attributes of the material are related to its structure, or topology, and not to the molecules it is made from.

“In our experiment we used an array of ceramic spheres, although the initial theoretical model used metallic subwavelength particles,” said Dr Miroshnichenko.

“Even though they are very different materials they gave the same result.”

In contrast with other international groups attempting to create topological insulators with large scale structures, the team used spheres that were smaller than the wavelength of the microwaves in their successful experiments.

Dr Poddubny devised the theory when he realised there was a direct analogy between quantum Kitaev’s model of Majorana fermions and optically coupled subwavelength scatterers.

Mr Slobozhanyuk said the team could control which parts of the material surface the light is channelled to by changing the polarisation of the light.

“This opens possibilities ranging from nanoscale light sources for enhancing microscopes, highly efficient antennas or even quantum computing,” he said.

“The structure couples the two sides of the material, so they could be used as entangled qubits for quantum computing.”

It would be nice to offer a link to a published paper but I cannot find one.

A multiferroic material for more powerful solar cells

A Nov. 12, 2014 INRS (Institut national de la recherche scientifique; Université du Québec) news release (also on EurekAlert), describes new work on solar cells from Federico Rosei’s laboratory (Note: Links have been removed; A French language version of the news release can be found here),

Applying a thin film of metallic oxide significantly boosts the performance of solar panel cells—as recentlydemonstrated by Professor Federico Rosei and his team at the Énergie Matériaux Télécommunications Research Centre at Institut national de la recherche scientifique (INRS). The researchers have developed a new class of materials comprising elements such as bismuth, iron, chromium, and oxygen. These“multiferroic” materials absorb solar radiation and possess unique electrical and magnetic properties. This makes them highly promising for solar technology, and also potentially useful in devices like electronic sensors and flash memory drives. …

The INRS research team discovered that by changing the conditions under which a thin film of these materials is applied, the wavelengths of light that are absorbed can be controlled. A triple-layer coating of these materials—barely 200 nanometres thick—captures different wavelengths of light. This coating converts much more light into electricity than previous trials conducted with a single layer of the same material. With a conversion efficiency of 8.1% reported by [Riad] Nechache and his coauthors, this is a major breakthrough in the field.

The team currently envisions adding this coating to traditional single-crystal silicon solar cells (currently available on the market). They believe it could increase maximum solar efficiency by 18% to 24% while also boosting cell longevity. As this technology draws on a simplified structure and processes, as well as abundant and stable materials, new photovoltaic (PV) cells will be more powerful and cost less. This means that the INRS team’s breakthrough may make it possible to reposition silicon PV cells at the forefront of the highly competitive solar energy market.

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

Bandgap tuning of multiferroic oxide solar cells by R. Nechache, C. Harnagea, S. Li, L. Cardenas, W. Huang,  J. Chakrabartty, & F. Rosei. Nature Photonics (2014) doi:10.1038/nphoton.2014.255 Published online
10 November 2014

This paper is behind a paywall although there is a free preview via ReadCube Access.

I last mentioned Federico Rose in a March 4, 2014 post about a talk (The exploration of the role of nanoscience in tomorrow’s energy solutions) he was giving in Vancouver (Canada).

University of Cambridge makes waves with graphene piano

The news about the graphene piano (and anti-fraud lasers, etc.) is contained in a report from the University of Cambridge’s Cambridge Innovation and Knowledge Centre (CIKC), according to a Nov. 5, 2013 news item on phys.org (Note: A link has been removed),

Two prototypes – a detection device which users lasers to fight fraud, and a piano which demonstrates the potential of printed electronics – have been unveiled by Cambridge researchers.

A detection device which uses printed lasers to identify counterfeit goods has been developed by researchers, who say that it could help to make products more resistant to fraud.

The detector is one of a number of innovations covered in a new report by the Cambridge Innovation and Knowledge Centre (CIKC), which has been developing advanced manufacturing technologies for photonics and electronics.

The same document also outlines a new method for printing graphene, showing how the one atom-thick material could be used to make cheap, printed electronics. Using a graphene-based ink, researchers have demonstrated this by creating a transparent, flexible piano.

Here’s a video about the transparent piano produced at Cambridge,

The Nov. 5, 2013 University of Cambridge news release, which originated the news item, offers details about the piano and the graphene inks used to produce it,

The printed piano meanwhile demonstrates the potential of using graphene in real applications where printed electronics might be needed – such as heart monitors and other sensors.

The research team behind it, Drs Tawfique Hasan, Felice Torrisi and Prof Andrea Ferrari, at the Cambridge Graphene Centre, have developed a graphene-based ink. Like the material itself, this has a number of interesting properties, including flexibility, optical transparency, and electrical conductivity.

Other conductive inks are made from precious metals such as silver, which makes them very expensive to produce and process, whereas graphene is both cheap, environmentally stable, and does not require much processing after printing. Graphene ink is also superior to conductive polymers in terms of cost, stability and performance.

The piano, designed in collaboration with Novalia Limited, shows off the graphene ink’s potential. The keys of the transparent piano are made from graphene-based inks, which have been printed on to a plastic film. These keys, working as electrodes, are connected to a simple electronic circuit-board, a battery and speaker. When a person touches a graphene electrode, the amount of electrical charge held in the key changes. This is then detected and redirected by the circuit to the speaker, creating the musical note.

The same research team, in collaboration with Printed Electronics Limited, has developed a flexible prototype digital display. This display uses conventional printable materials, but with a transparent, electrically conductive graphene layer on top. The graphene layer is not only a flexible but also more conductive and transparent than the conventional polymer it replaces. These simple displays can be used in a wide range of smart packaging applications such as toys, labelling and board games.

“Both of these devices show how graphene could be printed on to a whole range of surfaces, which makes it ideal for printed electronics,” Dr Hasan, the lead researcher behind the prototypes, said. For example, it might eventually be possible to print electronics on to clothing and to make wearable patches to monitor people with health conditions, such as a heart problem.”

Another potential application is cheap, printable sensors, which could be used to track luggage around an airport to ensure it is loaded on to the correct plane, or to follow products across a production and supply chain.

For anyone who’d like to see the report and get information on the other projects discussed in it just click on the title: Advanced Manufacturing Technologies for Photonics and Electronics – Exploiting Molecular and Macromolecular Materials: Final Report.

*’Unviersity in headline changed to University 11:11 am PDT Nov. 7, 2013.

Solar cells made even more leaflike with inclusion of nanocellulose fibers

Researchers at the US Georgia  Institute of Technology (Georgia Tech)  and Purdue University (Indiana) have used cellulose nanocrystals (CNC), which is also known as nanocrystalline cellulose (NCC), to create solar cells that have greater efficiency and can be recycled. From the Mar. 26, 2013 news item on Nanowerk,

Georgia Institute of Technology and Purdue University researchers have developed efficient solar cells using natural substrates derived from plants such as trees. Just as importantly, by fabricating them on cellulose nanocrystal (CNC) substrates, the solar cells can be quickly recycled in water at the end of their lifecycle.

The Georgia Tech Mar. 25, 2013 news release, which originated the news item,

The researchers report that the organic solar cells reach a power conversion efficiency of 2.7 percent, an unprecedented figure for cells on substrates derived from renewable raw materials. The CNC substrates on which the solar cells are fabricated are optically transparent, enabling light to pass through them before being absorbed by a very thin layer of an organic semiconductor. During the recycling process, the solar cells are simply immersed in water at room temperature. Within only minutes, the CNC substrate dissolves and the solar cell can be separated easily into its major components.

Georgia Tech College of Engineering Professor Bernard Kippelen led the study and says his team’s project opens the door for a truly recyclable, sustainable and renewable solar cell technology.

“The development and performance of organic substrates in solar technology continues to improve, providing engineers with a good indication of future applications,” said Kippelen, who is also the director of Georgia Tech’s Center for Organic Photonics and Electronics (COPE). “But organic solar cells must be recyclable. Otherwise we are simply solving one problem, less dependence on fossil fuels, while creating another, a technology that produces energy from renewable sources but is not disposable at the end of its lifecycle.”

To date, organic solar cells have been typically fabricated on glass or plastic. Neither is easily recyclable, and petroleum-based substrates are not very eco-friendly. For instance, if cells fabricated on glass were to break during manufacturing or installation, the useless materials would be difficult to dispose of. Paper substrates are better for the environment, but have shown limited performance because of high surface roughness or porosity. However, cellulose nanomaterials made from wood are green, renewable and sustainable. The substrates have a low surface roughness of only about two nanometers.

“Our next steps will be to work toward improving the power conversion efficiency over 10 percent, levels similar to solar cells fabricated on glass or petroleum-based substrates,” said Kippelen. The group plans to achieve this by optimizing the optical properties of the solar cell’s electrode.

The news release also notes the impact that using cellulose nanomaterials could have economically,

There’s also another positive impact of using natural products to create cellulose nanomaterials. The nation’s forest product industry projects that tens of millions of tons of them could be produced once large-scale production begins, potentially in the next five years.

One might almost  suspect that the forest products industry is experiencing financial difficulty.

The researchers’ paper was published by Scientific Reports, an open access journal from the Nature Publishing Group,

Recyclable organic solar cells on cellulose nanocrystal substrates by Yinhua Zhou, Canek Fuentes-Hernandez, Talha M. Khan, Jen-Chieh Liu, James Hsu, Jae Won Shim, Amir Dindar, Jeffrey P. Youngblood, Robert J. Moon, & Bernard Kippelen. Scientific Reports  3, Article number: 1536  doi:10.1038/srep01536 Published 25 March 2013

In closing, the news release notes that a provisional patent has been filed at the US Patent Office.And one final note, I have previously commented on how confusing the reported power conversion rates are. You’ll find a recent comment in my Mar. 8, 2013 posting about Ted Sargent’s work with colloidal quantum dots and solar cells.

Fireflies and their jagged scales lead to brighter LEDs (light emitting diodes)

According to the Jan. 8, 2013 news item on ScienceDaily, scientists have used an observation about fireflies to make brighter LEDs (light emitting diodes),

The nighttime twinkling of fireflies has inspired scientists to modify a light-emitting diode (LED) so it is more than one and a half times as efficient as the original.

Researchers from Belgium, France, and Canada studied the internal structure of firefly lanterns, the organs on the bioluminescent insects’ abdomens that flash to attract mates. The scientists identified an unexpected pattern of jagged scales that enhanced the lanterns’ glow, and applied that knowledge to LED design to create an LED overlayer that mimicked the natural structure. The overlayer, which increased LED light extraction by up to 55 percent, could be easily tailored to existing diode designs to help humans light up the night while using less energy.

The Optical Society of America’s Jan. 8, 2013 news release, which originated the news item, describes how the scientists came to make their observations,

“The most important aspect of this work is that it shows how much we can learn by carefully observing nature,” says Annick Bay, a Ph.D. student at the University of Namur in Belgium who studies natural photonic structures, including beetle scales and butterfly wings.  When her advisor, Jean Pol Vigneron, visited Central America to conduct field work on the Panamanian tortoise beetle (Charidotella egregia), he also noticed clouds of twinkling fireflies and brought some specimens back to the lab to examine in more detail.

Fireflies create light through a chemical reaction that takes place in specialized cells called photocytes. The light is emitted through a part of the insect’s exoskeleton called the cuticle.  Light travels through the cuticle more slowly than it travels through air, and the mismatch means a proportion of the light is reflected back into the lantern, dimming the glow. The unique surface geometry of some fireflies’ cuticles, however, can help minimize internal reflections, meaning more light escapes to reach the eyes of potential firefly suitors.

In Optics Express papers, Bay, Vigneron, and colleagues first describe the intricate structures they saw when they examined firefly lanterns and then present how the same features could enhance LED design. Using scanning electron microscopes, the researchers identified structures such as nanoscale ribs and larger, misfit scales, on the fireflies’ cuticles. When the researchers used computer simulations to model how the structures affected light transmission they found that the sharp edges of the jagged, misfit scales let out the most light. The finding was confirmed experimentally when the researchers observed the edges glowing the brightest when the cuticle was illuminated from below.

“We refer to the edge structures as having a factory roof shape,” says Bay.  “The tips of the scales protrude and have a tilted slope, like a factory roof.” The protrusions repeat approximately every 10 micrometers, with a height of approximately 3 micrometers. “In the beginning we thought smaller nanoscale structures would be most important, but surprisingly in the end we found the structure that was the most effective in improving light extraction was this big-scale structure,” says Bay.

Here’s how the scientists applied their observations to LEDs (from the news release),

Human-made light-emitting devices like LEDs face the same internal reflection problems as fireflies’ lanterns and Bay and her colleagues thought a factory roof-shaped coating could make LEDs brighter. In the second Optics Express paper published today, which is included in the Energy Express  section of the journal, the researchers describe the method they used to create a jagged overlayer on top of a standard gallium nitride LED. Nicolas André, a postdoctoral researcher at the University of Sherbrooke in Canada, deposited a layer of light-sensitive material on top of the LEDs and then exposed sections with a laser to create the triangular factory-roof profile. Since the LEDs were made from a material that slowed light even more than the fireflies’ cuticle, the scientists adjusted the dimensions of the protrusions to a height and width of 5 micrometers to maximize the light extraction.

“What’s nice about our technique is that it’s an easy process and we don’t have to create new LEDs,” says Bay.  “With a few more steps we can coat and laser pattern an existing LED.”

Other research groups have studied the photonic structures in firefly lanterns as well, and have even mimicked some of the structures to enhance light extraction in LEDs, but their work focused on nanoscale features. The Belgium-led team is the first to identify micrometer-scale photonic features, which are larger than the wavelength of visible light, but which surprisingly improved light extraction better than the smaller nanoscale features. The factory roof coating that the researchers tested increased light extraction by more than 50 percent, a significantly higher percentage than other biomimicry approaches have achieved to date. The researchers speculate that, with achievable modifications to current manufacturing techniques, it should be possible to apply these novel design enhancements to current LED production within the next few years.

For those who care to investigate further,

Both articles (HTML version) are open access; PDF versions were not checked.