INAE Monthly E-News Letter Vol. VIII, Issue 3, March 1, 2017

 (+) Academy Activities

 (+) Editorial Board, INAE

 (+) Articles by INAE Fellows

Dr Purnendu Ghosh
Dr Baldev Raj
Dr K V Raghavan
Dr Sanak Mishra
Prof. Indranil Manna
Prof BS Murty
Prof Sanghamitra Bandyopadhyay
Prof Pradip Dutta
Prof Manoj K Tiwari
Prof Sanjay Mittal
Prof Prasun K Roy
Brig Rajan Minocha

 (+) Engineering and Technology Updates

  Civil Engineering

  Computer Engineering  and Information Technology

  Mechanical Engineering

  Chemical Engineering

  Electrical Engineering

  Electronics and Communication Engineering

  Aerospace Engineering

  Mining, Metallurgical and Materials Engineering

  Energy Engineering

  Interdisciplinary Engineering and Special Fields 

 (+) Engineering Innovation in India
 (+) Previous E-newsletter

 

Civil Engineering

1. How to Inflate a Huge Hardened Concrete Shell

Finished concrete shell after the transformation process.

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of labour and material. A very resource efficient alternative construction method called “Pneumatic Forming of Hardened Concrete (PFHC)” was invented at TU Wien by researchers at the Institute of Structural Engineering. A simple air cushion and additional post-tensioning tendons transform a flat concrete plate into a double curved shell. Thus, the complicated spatially curved formwork and the framework are redundant. The Austrian Federal Railways Infrastructure (ÖBB Infrastruktur) are currently building a first test construction on a scale of 1:2 in Carinthia, in the south of Austria, which will later serve as event canopy.The functioning of the construction method is comparatively easy: At first a flat concrete plate with wedge-shaped outlets is casted. After the concrete is hardened, the air cushion placed underneath the plate is inflated and the post-tensioning tendons at the circumference are tensioned until the final form is reached. Glass fibre reinforced plastic rods used as reinforcement absorb the occurring strains in the concrete plate. If the flat plate is produced with high accuracy, the construction method allows to build very precise concrete shells. The method also saves up to 50 percent of the concrete as well as 65 percent of the necessary reinforcement steel.The test dome, built on behalf of the ÖBB Infrastruktur, has a length of 26.5 m, a width of 19.1 m and a height of 4.2 m. It will be used it to improve the construction technique for a first large application on a deer pass over the twin-track railway line “Koralmbahn” in 2017. Recently, the transformation process of the test dome was successfully finished, weighing 80 t and lifted with only 20-22 millibar from the flat plate to the spatially curved shell. The very smooth surface results from a sophisticated geometry optimization. “We could improve the construction method once again decisively during the preparation of the project for this first application,” explains a researcher. In the next work steps, an additional concrete layer will be applied and some areas will be cut away. The final building can already be used for events in summer 2017.

 

Source : https://www.sciencedaily.com/releases/2017/01/170111102903.htm

 

Computer Engineering and Information Technology

2.  Watching Computers Think

Fraunhofer HHI’s analysis software uses algorithms to visualize complex learning processes (schematic diagram)

Neural networks are commonly used today to analyze complex data — for instance to find clues to illnesses in genetic information. Ultimately, though, no one knows how these networks actually work exactly. That is why Fraunhofer researchers developed software that enables them to look into these black boxes and analyze how they function. Sorting photos on the computer used to be a tedious job. Today, you simply click on face recognition and instantly get a selection of photos required. Computers are very good at analyzing large volumes of data and searching for certain structures, such as faces in images. This is made possible by neural networks, which have developed into an established and sophisticated IT analysis method. The problem is that it isn’t just researchers who currently don’t know exactly how neural networks function step by step, or why they reach one result or another. Neural networks are, in a sense, black boxes — computer programs that people feed values into and that reliably return results. If you want to teach a neural network, for instance, to recognize cats, then you instruct the system by feeding it thousands of cat pictures. Just like a small child that slowly learns to distinguish cats from dogs, the neural network, too, learns automatically. “In many cases, though, researchers are less interested in the result and far more interested in what the neural network actually does — how it reaches decisions,” says head of the Machine Learning Group at Fraunhofer Heinrich Hertz Institute HHI in Berlin. The researchers, in collaboration with colleagues from TU Berlin, developed a method that makes it possible to watch a neural network think.This is important, for instance, in detecting diseases. We already have the capability today to feed patients’ genetic data into computers — or neural networks — which then analyze the probability of a patient having a certain genetic disorder. “But it would be much more interesting to know precisely which characteristics the program bases its decisions on,” says a researcher. It could be certain genetic defects the patient has — and these, in turn, could be a possible target for a cancer treatment that is tailored to individual patients.The researchers’ method allows them to watch the work of the neural networks in reverse: they work through the program backwards, starting from the result. “We can see exactly where a certain group of neurons made a certain decision, and how strongly this decision impacted the result,” says a researcher. The researchers have already impressively demonstrated — multiple times — that the method works. For instance, they compared two programs that are publicly available on the Internet and that are both capable of recognizing horses in images. The result was surprising. The first program actually recognized the horses’ bodies. The second one, however, focused on the copyright symbols on the photos, which pointed to forums for horse lovers, or riding and breeding associations, enabling the program to achieve a high success rate even though it had never learned what horses look like. This knowledge is also of particular interest to industry. It is conceivable, for instance, that the operating data of a complex production plant could be analyzed to deduce which parameters impact product quality or cause it to fluctuate. The invention is also interesting for many other applications that involve the neural analysis of large or complex data volumes. According to the researchers, for a long time banks have even been using neural networks to analyze bank customers’ creditworthiness. To do this, large volumes of customer data are collected and evaluated by a neural network. “If we knew how the network reaches its decision, we could reduce the data volume right from the start by selecting the relevant parameters,” he says.



Source : https://www.sciencedaily.com/releases/2017/02/170206084104.htm
 

 

Mechanical Engineering

3.  Nano-Level Lubricant Tuning Improves Material for Electronic Devices and Surface Coatings

This is a scanning electron microscope image of atomically-thin MoS2 with hierarchical, dual-scale structure

Molybdenum disulfide (MoS2), which is ubiquitously used as a solid lubricant, has recently been shown to have a two-dimensional (2D) form that is similar to graphene. But, when thinned down to less than a nanometer thick, MoS2 demonstrates properties with great promise as a functional material for electronic devices and surface coatings.Researchers at the University of Illinois at Urbana-Champaign have developed a new approach to dynamically tune the micro- and nano-scale roughness of atomically thin MoS2, and consequently the appropriate degree of hydrophobicity for various potential MoS2-based applications.”The knowledge of how new materials interact with water is a fundamental,” explained SungWoo Nam, an assistant professor of mechanical science and engineering at Illinois. “Whereas the wettability of its more famous cousin, graphene, has been substantially investigated, that of atomically thin MoS2 — in particular atomically thin MoS2 with micro- and nano-scale roughness — has remained relatively unexplored despite its strong potential for fundamental research and device applications. Notably, systematic study of how hierarchical microscale and nanoscale roughness of MoS2 influence its wettability has been lacking in the scientific community.””This work will provide a new approach to dynamically tune the micro- and nano-scale roughness of atomically thin MoS2 and consequently the appropriate degree of hydrophobicity for various potential MoS2-based applications,” stated a researcher. “These include waterproof electronic devices with superhydrophobicity with water contact angle greater than 150 degrees. It may also be useful for medical applications with reduced hydrophobicity (WCA less than 100 degrees) for effective contact with biological substances. “According to the authors, this study, expands the toolkit to allow tunable wettability of 2D materials, many of which are just beginning to be discovered.”When deformed and patterned to produce micro- and nano-scale structures, MoS2 shows promise as a functional material for hydrogen evolution catalysis systems, electrodes for alkali metal-ion batteries, and field-emission arrays,” Nam added. “The results should also contribute to future MoS2-based applications, such as tunable wettability coatings for desalination and hydrogen evolution.”



Source: https://www.sciencedaily.com/releases/2017/02/170210165951.htm
 

 

Chemical Engineering

4.  Highly Sensitive Gas Sensors for Volatile Organic Compound Detection

Volatile organic compounds (VOCs) are a group of carbon-based chemicals with low evaporation or vaporization points. Some VOCs are harmful to animal or environmental health so sensing these gases is important for maintaining health and safety. VOCs also occur in nature and can be useful in medical diagnostics, which require highly sensitive sensors to be effective.In an effort to improve VOC detection, a collaboration of Japanese researchers from Kumamoto University, Fukuoka Industrial Technology Center, and Tohoku University set out to improve sensor sensitivity by modifying the particle and pore sizes of Tin-dioxide (SnO2) nanocrystals on sensing film. They knew that particle size was a determining factor in sensor response, so they formulated a method to synthesize SnO2particles of different sizes and pore distribution patterns, and ran an analysis to determine optimal sensor film particle morphology for various gases.Using a hydrothermal method, the researchers synthesized SnO2nanocubes and nanorods, and created gas-sensing films of various pore and particle sizes. Nanocrystals created in this experiment were developed using organic molecules in an acidic solution, which is a major difference from previous experiments that used cations in an alkaline solution. Films made from nanocubes had very small pores, less than 10 nm, whereas films made with nanorods were distinctly porous with pore sizes larger than 10 nm. Palladium (Pd)-loaded SnO2 nanocrystals were also synthesized to test the idea that Pd-loading would improve sensor response by changing pore sizes. The gases used to test the new sensors were hydrogen (200 ppm), ethanol (100 ppm), and acetone (100 ppm), each of which are known biomarkers for glucose malabsorption, alcohol intoxication, and diabetic ketoacidosis respectively. Sensor response (S) was calculated using a ratio of electrical resistance produced in air (Ra) to the resistance produced by the testing gas (Rg) (S=Ra/Rg).The research team found that the sensors had the best response when using long (500 nm) nanorods at a temperature of approximately 250 degrees Celsius, except for the H2 sensor, which responded best at a temperature of 300 degrees Celsius with nanocubes. Furthermore, Pd-loaded sensors had an improved response at 250 degrees Celsius with long nanorods being the best performing nanocrystal morphology for each of the gasses tested. “Our experiments show that the TiO2 nanocrystal sensors with larger pore sizes gave the best sensor responses. In particular, we found ultra-high sensitivity (increasing by five orders of magnitude) in the devices with largest pore size, the long nanorod sensors,” said a researcher at Kumamoto University. “This tells us that is beneficial to have precise control over the manufacturing methods of these types of sensors.”Simulations have estimated ethanol detection levels to be in the lower parts-per-billion range, meaning that the devices could feasibly detect alcohol biomarkers in a patient’s breath.One drawback of the new sensors is their relatively long recovery time. Even though the response time was swift, between 15 and 21 seconds, the recovery time fell between 157 to 230 minutes. This was thought to be caused by reaction byproducts remaining on the surface of the sensor film. Additionally, experimental and simulation results for ethanol showed that sensors with pore sizes over 80 nm are prone to saturate. However, it is likely that this can be overcome by pore size optimization and controlling the sensor film electrical resistance.



Source: https://www.sciencedaily.com/releases/2017/02/170201092613.htm
 

 

Electrical Engineering

5. 1000 Times More Efficient Nano-LED Opens Door to Faster Microchips

This is a scanning electron microscope picture of the new nano-LED, including some details.

The electronic data connections within and between microchips are increasingly becoming a bottleneck in the exponential growth of data traffic worldwide. Optical connections are the obvious successors but optical data transmission requires an adequate nanoscale light source, and this has been lacking. Scientists at Eindhoven University of Technology (TU/e) now have created a light source that has the right characteristics: a nano-LED that is 1000 times more efficient than its predecessors, and is capable of handling gigabits per second data speeds. With electrical cables reaching their limits, optical connections like fiberglass are increasingly becoming the standard for data traffic. Over longer distances almost all data transmission is optical. Within computer systems and microchips, too, the growth of data traffic is exponential, but that traffic is still electronic, and this is increasingly becoming a bottleneck. Since these connections (‘interconnects’) account for the majority of the energy consumed by chips, many scientists around the world are working on enabling optical (photonic) interconnects. Crucial to this is the light source that converts the data into light signals which must be small enough to fit into the microscopic structures of microchips. At the same time, the output capacity and efficiency have to be good. Especially the efficiency is a challenge, as small light sources, powered by nano- or microwatts, have always performed very inefficiently to date.Researchers at TU Eindhoven have now developed a light-emitting diode (LED) of some hundred nanometers with an integrated light channel (waveguide) to transport the light signal. This integrated nano-LED is a 1000 times more efficient than the best variants developed elsewhere. The Eindhoven-based researchers have especially made progress in the quality of the integrated coupling of the light source and the waveguide whereby much less light is lost and therefore far more light enters the waveguide. The efficiency of the new nano-LED currently lies between 0.01 and 1 percent, but the researchers expect to be well above that figure soon thanks to a new production method.Another key characteristic of the new nano-LED is that it is integrated into a silicon substrate on a membrane of indium phosphide. Silicon is the basic material for microchips but is not suitable for light sources whereas indium phosphide is. Furthermore, tests reveal that the new element converts electrical signals rapidly into optical signals and can handle data speeds of several gigabits per second.The researchers in Eindhoven believe that their nano-LED is a viable solution that will take the brake off the growth of data traffic on chips. However, they are cautious about the prospects. The development is not yet at the stage where it can be exploited by the industry and the production technology that is needed still has to get off the ground.



Source : https://www.sciencedaily.com/releases/2017/02/170202122739.htm
 

 

Electronics and Communication Engineering

6. Three magnetic states for each hole: Researchers investigate the potential of metal grids for electronic components

Researchers at the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have calculated that the specific layout of four holes (“antidots”) in a layer of cobalt will accommodate 15 different combinations for programming.

Nanometer-scale magnetic perforated grids could create new possibilities for Computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition, they discovered that for every hole (“antidot”) three magnetic states can be configured. Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in order to program its magnetic properties. His colleagues from the National University in Singapore produced the grid using a photolithographic process similar to that currently used in chip manufacture. Approximately 250 nanometers sized holes, so-called antidots, were created at regular intervals — with interspaces of only 150 nanometers — in the cobalt layer. In order to be able to stably program it, the Singapore experts followed the Dresden design, which specified a metal layer thickness of approximately 50 nanometers.At these dimensions the cobalt antidot grid displayed interesting properties: Dr. Bali’s team discovered that with the aid of an externally applied magnetic field three distinct magnetic states around each hole could be configured. The scientists called these states “G,” “C” and “Q.” Dr. Bali: “Antidots are now in the international research spotlight. By optimizing the antidot geometry we were able to show that the spins, or the magnetic moments of the electrons, could be reliably programmed around the holes.”Since the individually programmable holes are situated in a magnetic metal layer, the grid geometry has potential use in computers that would work with spin-waves instead of electric current. “Spin-waves are similar to the so-called Mexican waves you see in a football stadium. The wave propagates through the stadium, but the individual fans, in our case the electrons, stay seated,” explains Dr. Bali. Logic chips utilizing such spin-waves would use far less power than today’s processors, because no electrical current is involved.Many magnetic states can be realized in the perforated grid so that the spin-waves can, for example, be assigned specific directions. This could allow for a higher processing speed in future logic chips. “Our perforated grids could also operate as components for future circuits working with spin-waves,” estimates Dr. Bali. A researcher is now investigating the dynamics developed by the spin-waves in such perforated grids. Among other aspects he is participating in the development of special computer programs making possible the complex calculation of the magnetic states in perforated grids.



Source: https://www.sciencedaily.com/releases/2017/02/170202122714.htm
 

 

Aerospace Engineering

7. ISRO Sets World Record by Successfully Launching 104 Satellites in Single Mission

ISRO launched a record 104 satellites on a single rocket from the Sriharikota spaceport in Andhra Pradesh on Feb 15, 2017. India has become the first country to successfully carry so many satellites in a single mission. The Polar Satellite Launch Vehicle PSLV-C37 is the star of what has been described as an incredible step for the country’s space programme. It tore into the sky at 9.28 am, breaking free of the earth’s gravitational pull. The countdown began by successfully launching a record 104 satellites, including country’s Cartosat-2 earth observation satellite, in a single mission from Sriharikota, Andhra Pradesh. Exactly at 9:28 am, ISRO’s Polar Satellite Launch Vehicle PSLV-C37 carrying 104 satellites blasted off from the first launch pad at the Satish Dhawan Space Centre.About 28 minutes into the flight, PSLV first injected Cartosat-2 series satellite into orbit, followed by the other 103 nano satellites, including 96 from the US, in a gap of about 30 minutes.This is the highest number of satellites ever launched in a single mission.In about 18 minutes, all 104 satellites were released into space, each travelling at the speed of over 27,000 km per hour – 40 times the speed of an average passenger airline. ISRO’s new feat beat superpowers like Russia, which had launched 37 satellites in one go in 2014, and the US, which orbited 29 satellites in 2013.In this complex mission after the end of 28-hour countdown, the PSLV-C37 injected the 714 kg Cartosat-2 series satellite followed by ISRO’s nano satellites INS-1A and INS-1B in a 505 km polar Sun Synchronous Orbit (SSO).This was followed by launch of the other 101 nano satellites of overseas customers in blocks in a series of separations.INS-1A and INS-1B will carry a total of four different payloads from Space Applications Centre (SAC) and Laboratory for Electro Optics Systems (LEOS) of ISRO for conducting various experiments, ISRO saidCartosat-2 series satellite, with a mission life of five years, will send images that would cater to coastal land use and regulation, road network monitoring, distribution of water, creation of land use maps among others. Ten important points of the mission are summarized below.

  1. PSLV-C37 Project Director B Jayakumar said it was a “great moment for each and everyone of us. It is confirmed all 104 satellites have been successfully deployed in the orbit.“Launching 104 satellites onboard a single rocket was a complex mission.
  2. India’s workhorse rocket PSLV-C37 is on its 39th mission. Among the 104 satellites are many belonging to international customers.
  3. This is the heaviest version of the PSLV, weighing about 320 tonnes at lift-off and standing tall at 44.4 meters.
  4. The main passenger is the Earth-mapping Cartosat 2 series satellite, which weighs 714 kg.The smaller satellites belong to the US, Israel, Kazakhstan, Netherlands,Switzerland, United Arab Emirates will be launched. 96 of the satellites belong to the US.
  5. Close to 90 small satellites named ‘Doves’ belong to one San Francisco-based company, Planet Inc. The Dove constellation will be used to image the earth at low cost.
  6. Two ISRO-made Nano satellites belonging to international customers were also launched. They weigh about 1,378 kg.
  7. The PSLV first launched the Cartosat-2 and then its 103 co-passengers into the polar Sun Synchronous Orbit, about 520 km from the Earth.
  8. PM Narendra Modi congratulated the scientists for successful launch, saying “this remarkable feat has made India proud”.
  9. In 2014, the Russian Space Agency has launched 37 satellites in one go.
  10. This is ISRO’s second successful attempt after the launch of 23 satellites in a single rocket in June 2015.


Source : http://zeenews.india.com/space/isro-sets-world-record-by-successfully-launching-104-satellites-in-single-mission_1977330.html
 

 

Mining, Metallurgical and Materials Engineering

 

8.  Automatically Darkening Windows ina Wide Range of Colours

Organic monomers mixed into a special resin darken window glass.

In winter, when the sun sets earlier in the afternoon in Europe, people are happy to catch every last sunbeam. On hot summer days, however, office workers are keen to do without extra heat from the sun. Electrochromic glass offers a solution: When it’s gloomy outside, the glass remains transparent and lets through light and heat. But when the sun is blazing, the windows darken to keep most of the heat outside. These panes shimmer in a lovely shade of blue — up to now, other colours were not possible.Researchers at the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam-Golm, in cooperation with TILSE FORMGLAS GmbH, have now developed a new manufacturing method for such electrochromic glass panes. How do electrochromic panes work? In most cases, manufacturers use glass that has been coated with a thin film of translucent indium tin oxide or the less expensive fluorine-doped tin oxide. This coating makes the glass electrically conductive. Two panes are required to make a smart window pane. First, one of the panes receives a second, vapor-deposited coating consisting of electrochromic tungsten oxide. Next, the panes are layered on top of each other with the coatings facing each other and a gel-like electrolyte in between. When a voltage is applied to the glass, the tungsten oxide coating darkens. When the polarization is reversed, the pane brightens again. This takes time — in the case of large windows of two to three square meters, it may take up to 15 to 20 minutes before the pane is completely darkened.Fraunhofer IAP’s researchers are focusing on a different technology to darken the panes. “We use organic monomers that have been mixed into specially developed resin,” says a researcher. Although the researchers are using glass panes coated with tin oxide as an initial substrate, just like existing processes do, they are skipping the second coating. Instead, they layer the panes with the tin oxide coating facing inwards and fill the space between them with the resin and electrochromic molecule mix. The resin is then cured using heat or UV radiation. Next, the researchers apply direct current to ensure that the monomers on an electrode bond to form an electrochromic polymer.This means that the pane can be switched at a significantly lower voltage. Meanwhile, using an organic colorant offers various advantages. For one thing, by selecting other monomers, it will be possible to install red or purple panes in the future. Furthermore, monomers react significantly faster. “A 1.2-square-meter pane can darken in just 20 to 30 seconds; the standard tungsten-oxide-based electrochromic system would take at least ten minutes for that,” says the researcher.Sturdiness is also a point in favour for the new process. “We tested the stability of our new electrochromic panes in accordance with applicable DIN standards. Even a pane comprising just two layers is sturdy enough for use as overhead glazing or in surfaces meant to be walked on. Previously you needed many more for that,” says the researcher. With the special resin, this means that it is possible to save on material costs because only two panes are needed instead of three or four. For the first time, these can also be electrochromically switched. Furthermore, the glass is also suitable for ship building. The researchers have already produced a prototype of the electrochromic resin glazing. While their current prototype switches to blue, in the next step researchers plan to implement other colours such as red.



Source : https://www.sciencedaily.com/releases/2017/02/170207104235.htm
 

 

Energy Engineering 

9. New Technique Could Lead to Safer, More Efficient Uranium Extraction

A diagram, top, and photograph show uranium clusters being extracted upward from an aqueous solution into a kerosene solution.

The separation of uranium, a key part of the nuclear fuel cycle, could potentially be done more safely and efficiently through a new technique developed by chemistry researchers at Oregon State University.The technique uses soap-like chemicals known as surfactants to extract uranium from an aqueous solution into a kerosene solution in the form of hollow clusters. Aside from fuel preparation, it may also find value in legacy waste treatment and for the clean-up of environmental contamination.The research at OSU involves a unique form of uranium discovered in 2005, uranyl peroxide capsules, and how those negatively charged clusters form in alkaline conditions. “This is a very different direction,” said study lead researcher in Oregon State’s College of Science. “A lot of the work done now is in acid, and we’re at the other end of the pH scale in base. It’s a very different approach, overall using less harmful, less toxic chemicals.”Throughout the nuclear fuel cycle, many separations are required — in mining, enrichment and fuel fabrication, and then after fuel use, for the recovery of usable spent isotopes and the encapsulation and storage of unusable radioactive components.”When you use nuclear fuel, the radioactive decay products poison the fuel and make it less effective,” said a researcher at Oregon State. “You have to take it, dissolve it, get the good stuff out and make new fuel.” He notes the work represents significant fundamental research in the field of cluster chemistry because it allows for the study of uranyl clusters in the organic phase and can pave the way to improved understanding of ion association.”With extracting these clusters into the organic phase, the clusters themselves are hollow, so when we get them into the organic solution, they’re still containing other atoms, molecules, other ions,” he added. “We can study how these ions interact with these cages that they’re in. The fundamental research is understanding how the ions get inside and what they do once they’re inside because they’re stuck there.”When the clusters form, each contains 20 to 60 uranium atoms, “so we can extract them in whole bunches instead of one at a time,” a researcher said. “It’s an atom-efficient approach.”Existing separation techniques require two extraction molecules for every uranium ion, whereas the OSU technique requires less than one extraction molecule per ion.



Source : https://www.sciencedaily.com/releases/2017/01/170126130859.htm
 

 

Interdisciplinary Engineering and Special Fields

10. Novel Liquid Crystal Could Triple Sharpness of Today’s Televisions

Researchers have developed a new technology that could triple the resolution density of displays. The new technology could allow field-sequential colour displays where a single subpixel can be quickly switched among red, green or blue. By eliminating the colour filters traditionally used to spatially divide one pixel into red, green or blue subpixels, field-sequential colour displays allow the three subpixels to become three independent pixels and thus triples the resolution density.

An international team of researchers has developed a new blue-phase liquid crystal that could enable televisions, computer screens and other displays that pack more pixels into the same space while also reducing the power needed to run the device. The new liquid crystal is optimized for field-sequential colour liquid crystal displays (LCDs), a promising technology for next-generation displays.”Today’s Apple Retina displays have a resolution density of about 500 pixels per inch,” said a researcher at the University of Central Florida’s College of Optics and Photonics (CREOL). “With our new technology, a resolution density of 1500 pixels per inch could be achieved on the same sized screen. This is especially attractive for virtual reality headsets or augmented reality technology, which must achieve high resolution in a small screen to look sharp when placed close to our eyes.”Although the first blue-phase LCD prototype was demonstrated by Samsung in 2008, the technology still hasn’t moved into production because of problems with high operation voltage and slow capacitor charging time. To tackle these problems, the research team worked with collaborators from liquid crystal manufacturer JNC Petrochemical Corporation in Japan and display manufacturer AU Optronics Corporation in Taiwan.The researchers report how combining the new liquid crystal with a special performance-enhancing electrode structure can achieve light transmittance of 74 percent with an operation voltage of 15 volts per pixel — operational levels that could finally make field-sequential colour displays practical for product development.”Field-sequential colour displays can be used to achieve the smaller pixels needed to increase resolution density,” said a researcher. “This is important because the resolution density of today’s technology is almost at its limit.”Today’s LCD screens contain a thin layer of nematic liquid crystal through which the incoming white LED backlight is modulated. Thin-film transistors deliver the required voltage that controls light transmission in each pixel. The LCD subpixels contain red, green and blue filters that are used in combination to produce different colours to the human eye. The colour white is created by combining all three colours.Blue-phase liquid crystal can be switched, or controlled, about 10 times faster than the nematic type. This sub-millisecond response time allows each LED colour (red, green and blue) to be sent through the liquid crystal at different times and eliminates the need for colour filters. The LED colours are switched so quickly that our eyes can integrate red, green and blue to form white.”With colour filters, the red, green and blue light are all generated at the same time,” said a researcher. “However, with blue-phase liquid crystal we can use one subpixel to make all three colours, but at different times. This converts space into time, a space-saving configuration of two-thirds, which triples the resolution density.”The blue-phase liquid crystal also triples the optical efficiency because the light doesn’t have to pass through colour filters, which limit transmittance to about 30 percent. Another big advantage is that the displayed colour is more vivid because it comes directly from red, green and blue LEDs, which eliminates the colour crosstalk that occurs with conventional colour filters. The team worked with JNC to reduce the blue-phase liquid crystal’s dielectric constant to a minimally acceptable range to reduce the transistor charging time and get submillisecond optical response time. However, each pixel still needed slightly higher voltage than a single transistor could provide. To overcome this problem, the researchers implemented a protruded electrode structure that lets the electric field penetrate the liquid crystal more deeply. This lowered the voltage needed to drive each pixel while maintaining a high light transmittance.”We achieved an operational voltage low enough to allow each pixel to be driven by a single transistor while also achieving a response time of less than 1 millisecond,” said a researcher. “This delicate balance between operational voltage and response time is key for enabling field sequential colour displays.””Now that we have shown that combining the blue-phase liquid crystal with the protruded electron structure is feasible, the next step is for industry to combine them into a working prototype,” said the lead researcher.



Source : https://www.sciencedaily.com/releases/2017/02/170201110628.htm

 
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