Tag Archives: Agency for Science Technology and Research

Brain-like computing with optical fibres

Researchers from Singapore and the United Kingdom are exploring an optical fibre approach to brain-like computing (aka neuromorphic computing) as opposed to approaches featuring a memristor or other devices such as a nanoionic device that I’ve written about previously. A March 10, 2015 news item on Nanowerk describes this new approach,

Computers that function like the human brain could soon become a reality thanks to new research using optical fibres made of speciality glass.

Researchers from the Optoelectronics Research Centre (ORC) at the University of Southampton, UK, and Centre for Disruptive Photonic Technologies (CDPT) at the Nanyang Technological University (NTU), Singapore, have demonstrated how neural networks and synapses in the brain can be reproduced, with optical pulses as information carriers, using special fibres made from glasses that are sensitive to light, known as chalcogenides.

“The project, funded under Singapore’s Agency for Science, Technology and Research (A*STAR) Advanced Optics in Engineering programme, was conducted within The Photonics Institute (TPI), a recently established dual institute between NTU and the ORC.”

A March 10, 2015 University of Southampton press release (also on EurekAlert), which originated the news item, describes the nature of the problem that the scientists are trying address (Note: A link has been removed),

Co-author Professor Dan Hewak from the ORC, says: “Since the dawn of the computer age, scientists have sought ways to mimic the behaviour of the human brain, replacing neurons and our nervous system with electronic switches and memory. Now instead of electrons, light and optical fibres also show promise in achieving a brain-like computer. The cognitive functionality of central neurons underlies the adaptable nature and information processing capability of our brains.”

In the last decade, neuromorphic computing research has advanced software and electronic hardware that mimic brain functions and signal protocols, aimed at improving the efficiency and adaptability of conventional computers.

However, compared to our biological systems, today’s computers are more than a million times less efficient. Simulating five seconds of brain activity takes 500 seconds and needs 1.4 MW of power, compared to the small number of calories burned by the human brain.

Using conventional fibre drawing techniques, microfibers can be produced from chalcogenide (glasses based on sulphur) that possess a variety of broadband photoinduced effects, which allow the fibres to be switched on and off. This optical switching or light switching light, can be exploited for a variety of next generation computing applications capable of processing vast amounts of data in a much more energy-efficient manner.

Co-author Dr Behrad Gholipour explains: “By going back to biological systems for inspiration and using mass-manufacturable photonic platforms, such as chalcogenide fibres, we can start to improve the speed and efficiency of conventional computing architectures, while introducing adaptability and learning into the next generation of devices.”

By exploiting the material properties of the chalcogenides fibres, the team led by Professor Cesare Soci at NTU have demonstrated a range of optical equivalents of brain functions. These include holding a neural resting state and simulating the changes in electrical activity in a nerve cell as it is stimulated. In the proposed optical version of this brain function, the changing properties of the glass act as the varying electrical activity in a nerve cell, and light provides the stimulus to change these properties. This enables switching of a light signal, which is the equivalent to a nerve cell firing.

The research paves the way for scalable brain-like computing systems that enable ‘photonic neurons’ with ultrafast signal transmission speeds, higher bandwidth and lower power consumption than their biological and electronic counterparts.

Professor Cesare Soci said: “This work implies that ‘cognitive’ photonic devices and networks can be effectively used to develop non-Boolean computing and decision-making paradigms that mimic brain functionalities and signal protocols, to overcome bandwidth and power bottlenecks of traditional data processing.”

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

Amorphous Metal-Sulphide Microfibers Enable Photonic Synapses for Brain-Like Computing by Behrad Gholipour, Paul Bastock, Chris Craig, Khouler Khan, Dan Hewak. and Cesare Soci. Advanced Optical Materials DOI: 10.1002/adom.201400472
Article first published online: 15 JAN 2015

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This article is behind a paywall.

For anyone interested in memristors and nanoionic devices, here are a few posts (from this blog) to get you started:

Memristors, memcapacitors, and meminductors for faster computers (June 30, 2014)

This second one offers more details and links to previous pieces,

Memristor, memristor! What is happening? News from the University of Michigan and HP Laboratories (June 25, 2014)

This post is more of a survey including memristors, nanoionic devices, ‘brain jelly, and more,

Brain-on-a-chip 2014 survey/overview (April 7, 2014)

One comment, this brain-on-a-chip is not to be confused with ‘organs-on-a-chip’ projects which are attempting to simulate human organs (Including the brain) so chemicals and drugs can be tested.

Purple promises and bioimaging from Singapore’s A*STAR

A May 7, 2014 news item on Nanowerk describes a promising new approach to bioimaging,

Labeling biomolecules with light-emitting nanoparticles is a powerful technique for observing cell movement and signaling under realistic, in vivo conditions. The small size of these probes, however, often limits their optical capabilities. In particular, many nanoparticles have trouble producing high-energy light with wavelengths in the violet to ultraviolet range, which can trigger critical biological reactions.

Now, an international team led by Xiaogang Liu from the A*STAR Institute of Materials Research and Engineering and the National University of Singapore has discovered a novel class of rare-earth nanocrystals that preserve excited energy inside their atomic framework, resulting in unusually intense violet emissions …

A May 7, 2014 A*STAR (Agency for Science, Technology and Research) news release (h/t Imagist), which originated the news item, describes the problems with current bioimaging techniques and the new approach in more detail (Note: Links have been removed)

Nanocrystals selectively infused, or ‘doped’, with rare-earth ions have attracted the attention of researchers, because of their low toxicity and ability to convert low-energy laser light into violet-colored luminescence emissions — a process known as photon upconversion. Efforts to improve the intensity of these emissions have focused on ytterbium (Yb) rare-earth dopants, as they are easily excitable with standard lasers. Unfortunately, elevated amounts of Yb dopants can rapidly diminish, or ‘quench’, the generated light.

This quenching probably arises from the long-range migration of laser-excited energy states from Yb and toward defects in the nanocrystal. Most rare-earth nanocrystals have relatively uniform dopant distributions, but Liu and co-workers considered that a different crystal arrangement — clustering dopants into multi-atom arrays separated by large distances — could produce localized excited states that do not undergo migratory quenching.

The team screened numerous nanocrystals with different symmetries before discovering a material that met their criteria: a potassium fluoride crystal doped with Yb and europium rare earths (KYb2F7:Eu). Experiments revealed that the isolated Yb ‘energy clusters’ inside this pill-shaped nanocrystal (see image) enabled substantially higher dopant concentrations than usual — Yb accounted for up to 98 per cent of the crystal’s mass — and helped initiate multiphoton upconversion that yielded violet light with an intensity eight times higher than previously seen.

The researchers then explored the biological applications of their nanocrystals by using them to detect alkaline phosphatases, enzymes that frequently indicate bone and liver diseases. When the team brought the nanocrystals close to an alkaline phosphate-catalyzed reaction, they saw the violet emissions diminish in direct proportion to a chemical indicator produced by the enzyme. This approach enables swift and sensitive detection of this critical biomolecule at microscale concentration levels.

“We believe that the fundamental aspects of these findings — that crystal structures can greatly influence luminescence properties — could allow upconversion nanocrystals to eventually outperform conventional fluorescent biomarkers,” says Liu.

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

Enhancing multiphoton upconversion through energy clustering at sublattice level by Juan Wang, Renren Deng, Mark A. MacDonald, Bolei Chen, Jikang Yuan, Feng Wang, Dongzhi Chi, Tzi Sum Andy Hor, Peng Zhang, Guokui Liu, Yu Han, & Xiaogang Liu. Nature Materials 13, 157–162 (2014) doi:10.1038/nmat3804 Published online 24 November 2013

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

Beautiful color printing for encoding high density data

Researchers at A*STAR (Agency for Science Technology and Research) based in Singapore have printed images at an extraordinary resolution of 100,000 dots per inch according to an Apr. 10, 2013 news item on ScienceDaily,

To print the image, the team coated a silicon wafer with insulating hydrogen silsesquioxane and then removed part of that layer to leave behind a series of upright posts of about 95 nanometers high. They capped these nanoposts with layers of chromium, silver and gold (1, 15 and 5 nanometers thick, respectively), and also coated the wafer with metal to act as a backreflector.

Each color pixel in the image contained four posts at most, arranged in a square. The researchers were able to produce a rainbow of colors simply by varying the spacing and diameter of the posts to between 50 nanometers and 140 nanometers.

When light hits the thin metal layer that caps the posts, it sends ripples — known as plasmons — running through the electrons in the metal. The size of the post determines which wavelengths of light are absorbed, and which are reflected …

Although the current process is not practical, it takes several hours to print an image there are some intriguing benefits,

Printing images in this way makes them potentially more durable than those created with conventional dyes. In addition, color images cannot be any more detailed: two adjacent dots blur into one if they are closer than half the wavelength of the light reflecting from them. Since the wavelength of visible light ranges about 380-780 nanometers, the nanoposts are as close as is physically possible to produce a reasonable range of colors.

The researchers believe there may be applications for anti-counterfeiting tags and encoding high density data.

You can read more about the work and find a citation and link to the researchers’ study published in Nature Nanotechnology at the ScienceDaily news item.

Are we creating a Star Trek world? T-rays and tricorders

There’s been quite a flutter online (even the Huffington Post has published a piece) about ‘Star Trek-hand-held medical scanners’ becoming possible due to some recent work in the area of T-rays. From the Jan. 20, 2012 news item on Nanowerk,

Scientists who have developed a new way to create a type of radiation known as Terahertz (THz) or T-rays – the technology behind full-body security scanners – say their new, stronger and more efficient continuous wave T-rays could be used to make better medical scanning gadgets and may one day lead to innovations similar to the “tricorder” scanner used in Star Trek.

In a study published recently in Nature Photonics (“Greatly enhanced continuous-wave terahertz emission by nano-electrodes in a photoconductive photomixer” [behind a paywall]), researchers from the Institute of Materials Research and Engineering (IMRE), a research institute of the Agency for Science, Technology and Research (A*STAR) in Singapore and Imperial College London in the UK have made T-rays into a much stronger directional beam than was previously thought possible and have efficiently produced T-rays at room-temperature conditions. This breakthrough allows future T-ray systems to be smaller, more portable, easier to operate, and much cheaper.

For anyone who’s not familiar with ‘Star Trek world’ and tricorders, here’s a brief description from a Wikipedia essay about tricorders,

In the fictional Star Trek universe, a tricorder is a multifunction handheld device used for sensor scanning, data analysis, and recording data.

David Freeman in his Jan. 21, 2012 article for the Huffington Post about the research puts it this way,

Trekkies, take heart. A scientific breakthrough involving a form of infrared radiation known as terahertz (THz) waves could lead to handheld medical scanners reminiscent of the “tricorder” featured on the original Star Trek television series.

What’s the breakthrough? Using nanotechnology, physicists in London and Singapore found a way to make a beam of the”T-rays”–which are now used in full-body airport security scanners–stronger and more directional.

Here’s how the improved T-ray technology works (from the Jan. 20, 2012 news item on Nanowerk),

In the new technique, the researchers demonstrated that it is possible to produce a strong beam of T-rays by shining light of differing wavelengths on a pair of electrodes – two pointed strips of metal separated by a 100 nanometre gap on top of a semiconductor wafer. The unique tip-to-tip nano-sized gap electrode structure greatly enhances the THz field and acts like a nano-antenna that amplifies the THz wave generated. The waves are produced by an interaction between the electromagnetic waves of the light pulses and a powerful current passing between the semiconductor electrodes from the carriers generated in the underlying semiconductor. The scientists are able to tune the wavelength of the T-rays to create a beam that is useable in the scanning technology.

Lead author Dr Jing Hua Teng, from A*STAR’s IMRE, said: “The secret behind the innovation lies in the new nano-antenna that we had developed and integrated into the semiconductor chip.” ….

Research co-author Stefan Maier, a Visiting Scientist at A*STAR’s IMRE and Professor in the Department of Physics at Imperial College London, said: “T-rays promise to revolutionise medical scanning to make it faster and more convenient, potentially relieving patients from the inconvenience of complicated diagnostic procedures and the stress of waiting for accurate results. Thanks to modern nanotechnology and nanofabrication, we have made a real breakthrough in the generation of T-rays that takes us a step closer to these new scanning devices. …”

It’s another story about handheld (or point-of-care) diagnostic devices and I have posted on this topic previously:

  • Jan. 4, 2012 about work in Alberta;
  •  Dec. 22, 2011 on grants to scientists in the US and Canada working on these devices;
  •  Aug. 4, 2011 about a diagnostic device the size of a credit card;
  •  Mar. 1, 2011 about nanoLAB from Stanford University (my last sentence in that posting “It’s not quite Star Trek yet but we’re getting there.”); and,
  •  Feb. 5, 2011 about the Argento and PROOF initiatives.

I see I had four articles last year and this year (one month old), I already have two articles on these devices. It reflects my own interest, as well as, the amount work being done in this area.