Scientists design “paper” that could be written over and over again using UV light

Yuvaraj_RRI_AzobenzenegoldnpPaper, considered a symbol of knowledge, has been used indiscriminately in the past century causing severe environmental degradation. One study estimates that with all the paper we waste each year, we can build two 12-foot high wall of paper from New Delhi to Bangalore! Electronic storage is not a better alternative since it poses another challenge of handling e-waste that is generated. Now, a collaborative study by researchers headed by Prof. Sandeep Kumar and Dr. A.R Yuvaraj at Raman Research Institute (RRI), Bangalore, and the University of Malaysia, has developed a novel technology that could reduce the use of paper and the generation of e-waste by replacing the way we present information. The researchers have developed an optical storage device made of gold nanoparticles decorated with compounds called azobenzenes.

The newly developed device stores and displays information on a substrate and also restores the substrate back to its original state, using only light. “An optical storage device is a type of display device which can store energy, through light illumination”, explains Dr. A. R. Yuvaraj from RRI. The researchers started by reducing gold chloride to form gold nano-particles. The synthesized particles were then made to react with thiolated azobenzene moieties; chemicals that attach to the gold nano-particles, to form the azobenzene coated gold nanoparticle liquid crystal, measuring just around two nanometres on average. “One of the interesting things we noted was the difference in ways the molecules of this new compound is arranged in its liquid crystal form. Gold nanoparticles are usually arranged in well-defined planes. However, once the azobenzene molecules are attached, the compound loses this arrangement, which gives it some of its unique optical properties”, he adds.

For the new compound to function as an optical storage device, further fabrication of the liquid crystal is required. “We loaded the mixture of newly formed liquid crystal and commercially available LC (5CB) on to a Liquid Crystal prototype cell, made by sandwiching two polyimide coated, unidirectional substrates, which performs as an optical storage device”, explains Dr. Yuvaraj on how the team designed the optical storage device. Information can now be written onto the cell by simply shining UV light onto the cell through a photomask – a photographic pattern that covers some areas of the cell and is transparent to others. The areas that are exposed to light undergo a process called photoisomerization, which allows for information to be stored on the cell.

Photoisomerization is a process by which some molecules undergo a structural change, when energy, in the form of light, is given to the molecules. The molecules, which are in a stable configuration, called trans state, is changed into an unstable configuration, called cis state, on illumination. This allows for information to be written on the compound using photomasks. “Instead of using pens and markers to write, we can now write using just a UV pen. Once written, on shining light of around 450nm wavelength, which falls in the visible range, we can change the compound back to the trans state, thus erasing what was written. We can write and erase just using light”, remarks Dr. Yuvaraj.

The new device allows for easy storage of information by enabling simple writing, erasing and rewriting process all using light. It could replace writing boards in schools, advertisement and display boards, newspapers, magazines and anything that uses paper to store information. By designing the device for permanent optical storage, it could even replace business and ID cards. This innovation can help reduce the stress on trees, save water used for paper production, and reduce paper waste and e-waste, thus conserving our natural resources. A clean and a green way ahead, indeed!

Advertisements

Clearing the Haze: Scientists design a way to see through fog

In peering through a thick early morning mist or looking into a smoke-filled room or scanning muddy waters, we encounter a common problem – vision through such media gets obscured, and we cannot see what lies within. And many a times we have wanted to take pictures in foggy conditions, only to get a coarse image with no discernible features. ‘Seeing’ in these conditions would seem impossible without expensive equipments like thermal imaging cameras or radar technologies. The dream of that perfect picture on a foggy morning could be closer to reality, thanks to a new research. A collaborative study by scientists from Raman Research Institute (RRI), Bengaluru, and the University of Rennes, France are working to make seeing through the haze a reality. 

When a human eye or camera lens ‘sees’ an object, most of the light reflected from the object go straight in to the eye or lens. When a scattering medium, like a gas or fluids, fills the space between the eye and the object, the object appears obscured. This happens because of tiny suspended particles present in such media that scatters the particles light in random directions. “To capture an image, the light rays should travel in straight lines, or should be deviated in a predictable way, as in a lens. However, if the light is scattered in unpredictable ways, only a diffused illumination with no recognisable image is obtained” remarks Prof. Hema Ramachandran of the Raman Research Institute, who led this research activity.

Scientists have been trying for decades to overcome this impediment, as the ability to image through turbid media has a wide range of applications. A few techniques have been developed that either require lasers that give out bursts of light of very short duration or uses cameras that have very short exposure times, both of which are very expensive. Cheaper alternatives usually require much longer data collection and processing times. For most applications, however, one would like to form images in real time, with little or no delay.

Scientists from RRI and the University of Rennes have together addressed this problem, and have developed a simple, inexpensive, yet powerful solution. They have successfully demonstrated, for the first time, instant, real time imaging through strongly scattering media simulating a quarter of a kilometre of  fog. This was achieved without any sophisticated equipment like ultra-short pulsed lasers or ultrafast cameras.  Using an inexpensive LED light source, ordinary scientific camera and by performing computations using a typical desktop computer, they have successfully obtained images within a few thousandths of a second after the camera records the diffuse illumination shots. The images refresh at rates faster than the eye can perceive, thus providing flicker-free real-time images of the scene obscured by strong scattering media.

The research sees many applications where visibility through murky conditions is of significant importance. Medical professionals, pilots, rescuers and even adventurers and photographers, require a clear sight in low-visibility conditions.   “Such real-time imaging through strongly scattering media opens up innumerable possibilities for applications. Compact, low cost portable devices can be made, and used in many different areas. For example, aircraft landing under poor visibility, bio-medical imaging through flesh using ordinary light sources, rescue operations in smoke-filled environments are some areas that can utilise this development”, says  Prof. Ramachandran.

“Realtime imaging through strongly scattering media was achieved by a combination of ideas. The scene was illuminated with light that was modulated in intensity. Due to the strong turbidity of the intervening medium, most of the photons undergo repeated random scattering. Because of this, the unprocessed camera shots show only uniform, diffuse illumination, with no discernible feature. We then applied the concept of quadrature lock-in detection to the problem of distinguishing photons that have not been deviated from their original trajectories from the photons that have been randomly scattered” explains Prof. Ramachandran.

“Conventionally, scientists use the Fourier transform technique, where one takes a time series and finds out the strength of contribution at each frequency over a certain range, and then picks out the dominant frequency. Here, as we know the source modulation frequency, a lot of computation time can be saved by looking at just that one frequency. Not only that, unlike Fourier transform, where data has to be recorded for a length of time before the Fourier transform can be applied, in our approach, we can start the processing as soon as the first shot of diffused illumination is captured. This too is an enormous saving on time. Last, but not the least, we have utilised the wonderful parallel processing capabilities that even a typical desktop computer has. Using the Graphics Processing Unit (GPU) of the computer, we have carried out the computations for each pixel of the image in parallel. All these ideas put together have enabled more than a thousand-fold increase in imaging speed, that has enabled the instant extraction of the hidden scene”, she explains.
She goes on to say “Computers these days have very good GPU’s. Especially the ones used for gaming can already perform multiple tasks simultaneously. We have just utilized this data processing ability of the modern GPU along with our algorithm to successfully see through turbid medium. QLD is easily amenable to speed up on GPUs as compared to FFT”. Thus, by combining the strengths of the new algorithm – QLD, with currently available technology, the researchers have been able to cut down the data processing time by a significant margin. This allows them to capture an image in real time.

Technology today does allow us to see in a cloudy atmosphere with the help of infrared, x-ray and other imaging devices. But, apart from being expensive and often bulky, to be able to see features and details in an image, a camera that captures visible light would have to be used. The proposed new technique would progress the field of medicine, navigation, climate sciences and even space exploration by just recording clearer images and videos even in turbid conditions.

Now test the purity of milk you consume, on the spot…

Milk is considered to be one of the best sources of nutrients like protein, fat, carbohydrates and minerals making it an ideal food for infants and adults alike. The importance of milk to our dietary needs has made it a prime target for adulteration, the most common method known to us all being the addition of water. Unfortunately, it does not stop there. Harmful chemicals including melamine, formalin, detergents, sugars, urea and a host of other substances are used as adulterants. One common adulteration method used in India is to mix an emulsifier to vegetable oil resulting in a white paste. The paste is then diluted and mixed with chemicals like urea until the consistency of milk is achieved. The proportion of these ingredients is calculated to mimic the fat and solid not fat (SNF) percentages of unadulterated milk. The cost to human health and well being upon consumption of this synthetic milk is huge: it deprives consumers of the vital nutrients otherwise obtained from unadulterated milk while at the same time being harmful to health. Currently used testing based on fat and lactometer levels used to detect adulterated milk obviously fail in this scenario. Thus there is an urgent need for developing other measuring techniques to address and overcome this major health concern. For maximum societal impact the measuring platform should be cheap, easy to use, robust and precise with high sensitivity.

Prof. V. Lakshminarayan’s group at RRI has proposed a simple test that satisfies all the above requirements. The test is based on impedance measurement of the ionic constituents of normal milk vs. adulterated milk that can act as a first level screening to check for adulterated milk samples. Additionally, being a hand held device empowers the consumer to demand “on the spot” screening of milk samples.

The basic research was completed at RRI while collaborators in the Department of Electronics Systems and Engineering (DESE) design, Indian Institute of Science and the DST-National Hub for Health Care Instrumentation (NHHID) will undertake the product design and manufacture.

It is envisioned that a simple “Dip and Read” device can be made available at milk collection and distribution centers to rapidly assess for synthetic milk.

 

A picture of the hand held device to detect synthetic milkUntitled

SWAN-Sky Watch Array Network

 

 

Twinkle Twinkle Little star

How I wonder what you are

Shining with brilliant light

What have you got beyond my sight

 

From time immemorial human beings have wondered at the beautiful displays of light output by countless celestial objects in the night sky. Early attempts by astronomers at understanding the universe were confined to observations and analysis of output from objects that were visible to the human eye aided by optical telescopes. However, what the human eye can discern is just one small portion of the much larger output spectrum called the electromagnetic spectrum, which includes gamma rays, x-rays, ultraviolet, microwave and radio waves. On a fundamental level the above different forms of radiation are all the same, the difference lies in the frequency and wavelengths of oscillations. To the early astronomers the majority of the universe was literally hidden from plain sight.

We have come a long way from those early days – astronomers routinely collect light radiated by stars across most of the electromagnetic spectrum using specialized telescopes designed to collect specific frequency bands of radiation. For example astronomers use radio telescopes to study celestial objects at radio frequencies. Based on whether the radio output occurs continuously or in short bursts, celestial sources can be classified as steady state and transient. Right from the beginning radio astronomers have focused on steady state radio sources with some exceptions leading to exciting discoveries. A detailed study of the transient sky could also open up an entirely new dimension of astronomical exploration with a huge potential (which is presently difficult to quantify) for yet unanticipated discoveries of astronomical objects and phenomena. There is a need to facilitate and conduct searches and studies of fast (typically of sub-second duration) and slow transient radio radiation originating from astronomical sources. In fact studies show that transient events occur at a much higher rate than anticipated. To enable detection and proper analysis of such events requires an optimized setup that could routinely detect transient signals over a large volume of sky with required sensitivity.

Researchers at RRI have taken up this challenge by proposing Indian-SWAN (Sky Watch Array Network). SWAN is designed in such a way that it provides capabilities for reliable detection of energetic radio transients. One unique feature of SWAN is the opportunity it provides for bright and motivated students from across India to be involved directly in the realization of SWAN, including in the design, and also in the operation/usage of the setup for astronomical observations, as well as the follow-up/research. These opportunities have the potential to seed significant growth of future generations of Indian radio astronomers pursuing active research, including with future large telescopes.

Prof. Avinash Deshpande who is leading the project and is passionate about kindling interest in astronomy in the minds of young Indians says “The implicit aim is to initiate a collective effort to develop SWAN with as many of the 40+ technology and science institutes i.e. the (IIT, NIT, IISER & NISER)s, as well as some universities across India. The prospective institutes, particularly motivated people in these, will be approached for partnership. To prepare for student involvement, appropriate schools/workshops (in co-ordination with existing programs) are to be arranged to formally introduce under-grad and masters students to radio astronomy, basic concepts and advance topics/techniques, over a few weeks each year, along with hands-on experience with instrumentation. Active participation from the students in all aspects of the SWAN, including studies of astronomical sources, will be sought and explicitly encouraged/supported.”

DSC06458

Picture displaying one tile antenna of SWAN currently located at the Gauribidanur Radio Telescope Observatory

The more the merrier

Imagine two celestial objects – black holes – colliding and merging to form an even more massive black hole somewhere in deep space. Collisions and mergers such as these would be rather ubiquitous given the billions of black holes that probably dot our vast, perhaps somewhat cavernous Universe if you step just outside of Earth. But of course, with our limited technological prowess, probing the Universe’s mysteries remains out of reach – till early 2016, we had no way of directly detecting such a binary black hole merger.

Then on 11th February, 2016, the Advanced Laser Interferometer Gravitational-Wave Observatory (ALIGO) announced GW 150914, a binary black hole merger occurring on 14th September 2015 that resulted in the verification of General Relativity’s last remaining prediction – the existence of gravitational waves, powerful enough to distort our familiar four-dimensional space-time fabric. The masses involved were immense, the resultant black hole super-massive, and the energy radiated was more than the combined power of all light radiated by all stars in the thus-far observed Universe.

Physicists will tell you though that such a violent astrophysical event can hardly ever have only one tell-tale signature. 0.4 seconds after GW 150914, the Fermi Gamma-ray Burst Monitor (GBM) mounted on the Fermi Gamma-ray Space Telescope (FGST), had recorded a short gamma-ray burst (GRB).

Short GRBs are sources of extremely large amounts of energy concentrated within a very short interval of time and energetic enough to emit as much energy as our Sun does in 10 billion years. GRBs arise typically from a supernova explosion by way of which a high-mass star collapses to form a neutron star or a black hole, or perhaps from two colliding neutron stars.

Gamma-ray bursts consist of gamma-rays which are a form of electromagnetic radiation similar to X-rays, visible light or radio waves, the only difference being their underlying wavelength and the energy they bear. Along with gamma-rays though, GRBs dispense energy also in the form of highly accelerated protons. And where there are accelerated protons, can neutrinos be very far behind?

Neutrinos are uncharged, almost massless, almost non-interacting elementary particles that are everywhere around us. Forget your wonder at the dust particles you see floating in that sunbeam. A trillion neutrinos from the Sun pass through our eyes every second! Being almost non-interacting, they pass unhindered through normal matter. You need a billion kilometers of lead to detect a neutrino! But latest detectors such as the IceCube Neutrino Observatory in South Pole with its thousands of ultra-sensitive sensors buried under a cubic kilometer of dense Antarctic ice are catching up with these elusive particles.

GRBs may produce copious amounts of high-energy neutrinos (HENs). So what information do the HENs possibly associated with the GRB that was recorded 0.4s after GW150914 within the localization uncertainty limits of the GBM give us? That was precisely the question that a team of researchers from Raman Research Institute, Bengaluru, University of Johannesburg and Pennsylvania State University asked. They first theoretically modelled the GBM observation to find the amount of HENs that IceCube should detect from this short GRB and could find none. But this non-result placed an upper limit on the total energy released by this short GRB, which, incidentally turned out to be very small compared to that emitted in gravitational waves by GW150914.

No matter though, because combined HEN, GW and electromagnetic radiation studies of the Universe are here to stay – the more the merrier as the saying goes.

Dr. Nayantara Gupta, RRI says “We look forward to more instances of coinciding detections, because by combining such observations and theoretical modelling, we can learn not only from what we detect, but even what we do not.”

About the author and work:

Dr. Nayantara Gupta is an Associate Professor at the Department of Astronomy and Astrophysics at Raman Research Institute, Bengaluru. Contact: <nayan@rri.res.in>. For the publication see https://arxiv.org/pdf/1602.08436.pdf