Digital fabrication engineers are now working toward expanding the display capabilities of other everyday objects. One avenue they’re exploring is reprogrammable surfaces — or items whose appearances we can digitally alter — to help users present important information, such as health statistics, as well as new designs on things like a wall, mug, or shoe. Researchers from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL), the University of California at Berkeley, and Aarhus University have taken an intriguing step forward by fabricating “<a href="https://hcie.csail.mit.edu/research/portachrome/portachrome.html">PortaChrome</a>,” a portable light system and design tool that can change the color and textures of various objects. Equipped with ultraviolet (UV) and red, green, and blue (RGB) LEDs, the device can be attached to everyday objects like shirts and headphones. Once a user creates a design and sends it to a PortaChrome machine via Bluetooth, the surface can be programmed into multicolor displays of health data, entertainment, and fashion designs.<iframe width="640" height="360" src="https://www.youtube.com/embed/eQcwTSWOzR8?&amp;wmode=opaque&amp;rel=0&amp;enablejsapi=1&amp;origin=https://www.wevolver.com" frameborder="0" allowfullscreen="" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"></iframe>To make an item reprogrammable, the object must be coated with photochromic dye, an invisible ink that can be turned into different colors with light patterns. Once it’s coated, individuals can create and relay patterns to the item via the team’s graphic design software, or use the team’s API to interact with the device directly and embed data-driven designs. When attached to a surface, PortaChrome’s UV lights saturate the dye while the RGB LEDs desaturate it, activating the colors and ensuring each pixel is toned to match the intended design.Zhu and her colleagues’ integrated light system changes objects’ colors in less than four minutes on average, which is eight times faster than their prior work, “Photo-Chromeleon.” This speed boost comes from switching to a light source that makes contact with the object to transmit UV and RGB rays. Photo-Chromeleon used a projector to help activate the color-changing properties of photochromic dye, where the light on the object's surface is at a reduced intensity.“PortaChrome provides a more convenient way to reprogram your surroundings,” says Yunyi Zhu ’20, MEng ’21, an MIT PhD student in electrical engineering and computer science, affiliate of CSAIL, and lead author on a paper about the work. “Compared with our projector-based system from before, PortaChrome is a more portable light source that can be placed directly on top of the photochromic surface. This allows the color change to happen without user intervention and helps us avoid contaminating our environment with UV. As a result, users can wear their heart rate chart on their shirt after a workout, for instance.”<h2>Giving everyday objects a makeover</h2>In demos, PortaChrome displayed health data on different surfaces. A user hiked with PortaChrome sewed onto their backpack, putting it into direct contact with the back of their shirt, which was coated in photochromic dye. Altitude and heart rate sensors sent data to the lighting device, which was then converted into a chart through a reprogramming script developed by the researchers. This process created a health visualization on the back of the user’s shirt. In a similar showing, MIT researchers displayed a heart gradually coming together on the back of a tablet to show how a user was progressing toward a fitness goal.PortaChrome also showed a flair for customizing wearables. For example, the researchers redesigned some white headphones with sideways blue lines and horizontal yellow and purple stripes. The photochromic dye was coated on the headphones and the team then attached the PortaChrome device to the inside of the headphone case. Finally, the researchers successfully reprogrammed their patterns onto the object, which resembled watercolor art. Researchers also recolored a wrist splint to match different clothes using this process.Eventually, the work could be used to digitize consumers’ belongings. Imagine putting on a cloak that can change your entire shirt design, or using your car cover to give your vehicle a new look.<h2>PortaChrome’s main ingredients</h2>On the hardware end, PortaChrome is a combination of four main ingredients. Their portable device consists of a textile base as a sort of backbone, a textile layer with the UV lights soldered on and another with the RGB stuck on, and a silicone diffusion layer to top it off. Resembling a translucent honeycomb, the silicone layer covers the interlaced UV and RGB LEDs and directs them toward individual pixels to properly illuminate a design over a surface.This device can be flexibly wrapped around objects with different shapes. For tables and other flat surfaces, you could place PortaChrome on top, like a placemat. For a curved item like a thermos, you could wrap the light source around like a coffee cup sleeve to ensure it reprograms the entire surface.The portable, flexible light system is crafted with maker space-available tools (like laser cutters, for example), and the same method can be replicated with flexible PCB materials and other mass manufacturing systems.While it can also quickly convert our surroundings into dynamic displays, Zhu and her colleagues believe it could benefit from further speed boosts. They'd like to use smaller LEDs, with the likely result being a surface that could be reprogrammed in seconds with a higher-resolution design, thanks to increased light intensity.“The surfaces of our everyday things are encoded with colors and visual textures, delivering crucial information and shaping how we interact with them,” says Georgia Tech postdoc Tingyu Cheng, who was not involved with the research. “PortaChrome is taking a leap forward by providing reprogrammable surfaces with the integration of flexible light sources (UV and RGB LEDs) and photochromic pigments into everyday objects, pixelating the environment with dynamic color and patterns. The capabilities demonstrated by PortaChrome could revolutionize the way we interact with our surroundings, particularly in domains like personalized fashion and adaptive user interfaces. This technology enables real-time customization that seamlessly integrates into daily life, offering a glimpse into the future of ‘ubiquitous displays.’”Zhu is joined by nine CSAIL affiliates on the paper: MIT PhD student and MIT Media Lab affiliate Cedric Honnet; former visiting undergraduate researchers Yixiao Kang, Angelina J. Zheng, and Grace Tang; MIT undergraduate student Luca Musk; University of Michigan Assistant Professor Junyi Zhu SM ’19, PhD ’24; recent postdoc and Aarhus University assistant professor Michael Wessely; and senior author Stefanie Mueller, the TIBCO Career Development Associate Professor in the MIT departments of Electrical Engineering and Computer Science and Mechanical Engineering and leader of the HCI Engineering Group at CSAIL.

When Nikola Tesla predicted we’d have handheld phones that could display videos, photographs, and more, his musings seemed like a distant dream. Nearly 100 years later, smartphones are like an extra appendage for many of us.

A portable light system that can digitize everyday objects

CUDA Cores and Tensor Cores are specialized units within NVIDIA GPUs; the former are designed for a wide range of general GPU tasks, while the latter are specifically optimized to accelerate AI and deep learning through efficient matrix operations.

Tensor Cores vs CUDA Cores: The Powerhouses of GPU Computing from Nvidia

Swarm Garden interactive architecture exhibition, Lewis Arts Complex, Princeton University, Tuesday, April 9, 2024.

Inspired by nature, architecture and swarm intelligence, two Princeton Engineering professors created a wall of robotic “flowers” that visitors interacted with during a recent exhibition.

Swarm Garden brings robotic flowers to life

Holographic images have real depth because they are three dimensional, whereas monitors merely simulate depth on a 2D screen. Because we see in three dimensions, holographic images could be integrated seamlessly into our normal view of the everyday world.The result is a virtual and augmented reality display that has the potential to be truly immersive, the kind where you can move your head normally and never lose the holographic images from view. “To get a similar experience using a monitor, you would need to sit right in front of a cinema screen,” said <a href="https://engineering.princeton.edu/faculty/felix-heide" target="_blank">Felix Heide</a>, assistant professor of <a href="http://cs.princeton.edu/" target="_blank">computer science</a> and senior author on <a href="https://www.nature.com/articles/s41467-024-46915-3" target="_blank">a paper</a> published April 22 in Nature Communications.And you wouldn’t need to wear a screen in front of your eyes to get this immersive experience. Optical elements required to create these images are tiny and could potentially fit on a regular pair of glasses. Virtual reality displays that use a monitor, as current displays do, require a full headset. And they tend to be bulky because they need to accommodate a screen and the hardware necessary to operate it.“Holography could make virtual and augmented reality displays easily usable, wearable, and ultrathin,” said Heide. They could transform how we interact with our environments, everything from getting directions while driving, to monitoring a patient during surgery, to accessing plumbing instructions while doing a home repair.One of the most important challenges is quality. Holographic images are created by a small chip-like device called a spatial light modulator. Until now, these modulators could only create images that are either small and clear or large and fuzzy. This tradeoff between image size and clarity results in a narrow field of view, too narrow to give the user an immersive experience. “If you look towards the corners of the display, the whole image may disappear,” said Nathan Matsuda, research scientist at Meta and co-author on the paper.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1713912832170-Neural_Etendue_Expander_3_v2-1-2048x1152.png" style="width: 100%px;" class="fr-fic fr-dib">At left, an image produced using current holographic display technology. At right, the same image created using the new optical element invented by researchers at Princeton and Meta.Heide, Matsuda and&nbsp;<a href="https://ethan-tseng.github.io/" target="_blank">Ethan Tseng</a>, doctoral student in computer science, have&nbsp;<a href="https://light.princeton.edu/publication/neural-etendue-expander/" target="_blank">created a device</a> to improve image quality and potentially solve this problem. Along with their collaborators, they built a second optical element to work in tandem with the spatial light modulator. Their device filters the light from the spatial light modulator to expand the field of view while preserving the stability and fidelity of the image. It creates a larger image with only a minimal drop in quality.Image quality has been a core challenge preventing the practical applications of holographic displays, said Matsuda. “The research brings us one step closer to resolving this challenge,” he said.The new optical element is like a very small custom-built piece of frosted glass, said Heide. The pattern etched into the frosted glass is the key. Designed using AI and optical techniques, the etched surface scatters light created by the spatial light modulator in a very precise way, pushing some elements of an image into frequency bands that are not easily perceived by the human eye. This improves the quality of the holographic image and expands the field of view.Still, hurdles to making a working holographic display remain. The image quality isn’t yet perfect, said Heide, and the fabrication process for the optical elements needs to be improved. “A lot of technology has to come together to make this feasible,” said Heide. “But this research shows a path forward.”The paper, “Neural Etendue Expander for Ultra-Wide-Angle High-Fidelity Holographic Display” was published April 22 in Nature Communications. In addition to Heide and Tseng, co-authors from Princeton include Seung-Hwan Baek and Praneeth Chakravarthula. In addition to Matsuda, co-authors from Meta Research are Grace Kuo, Andrew Maimone, Florian Schiffers, and Douglas Lanman. Qiang Fu and Wolfgang Heidrich from the Visual Computing Center at King Abdullah University of Science and Technology in Saudi Arabia also contributed. The work was supported by Princeton University’s&nbsp;<a href="https://iac.princeton.edu/home.html" target="_blank">Imaging and Analysis Center</a> and the King Abdullah University of Science and Technology’s Nanofabrication Core Lab.

Researchers at Princeton and Meta have created a tiny optical device that makes holographic images larger and clearer. Small enough to fit on a pair of eyeglasses, the device could enable a new kind of immersive virtual reality display. Illustration by Liz Sabol, photo by Nathan Matsuda

Setting the stage for a new era of immersive displays, researchers are one step closer to mixing the real and virtual worlds in an ordinary pair of eyeglasses using high-definition 3D holographic images, according to a study led by Princeton University researchers.

Holographic displays offer a glimpse into an immersive future

Authors:&nbsp;<a href="https://www.linkedin.com/in/daandekubber/" rel="noreferrer noopener" target="_blank" data-hook="WebLink">Daan de Kubber</a>, <a href="https://www.linkedin.com/in/jurgenwesterhoff/" rel="noreferrer noopener" target="_blank" data-hook="WebLink">Jurgen Westerhoff</a>, <a href="https://www.linkedin.com/in/ben-robesin-4a41096/" rel="noreferrer noopener" target="_blank" data-hook="WebLink">Ben Robesin</a>&nbsp; SPGPrints b.v., Raamstraat 1-3, 5831 AT, Boxmeer, the NetherlandsPrinted electronics have gained significant attention for their potential to revolutionize various industries through cost-effective and scalable manufacturing processes. However, a critical challenge within this domain lies in the transition from lab-scale and pilot equipment to industrial-scale production. We want to shed light on the implications of this transition, emphasizing its impact on cost reduction, repeatability, and time to market.The initial stages of printed electronics development predominantly occur on lab and pilot equipment, where researchers and innovators prototype new applications. As these applications progress towards commercialization, the shift to industrial-scale equipment becomes inevitable. Rotary screen printing emerges as a prominent technique, providing high-throughput capabilities essential for large-scale production.<hr>We are Speaking at the Free-To-Attend On-Line Innovations Festival on 25 April 2024.&nbsp;<a href="https://www.techblick.com/innovation-festival-april-2024" target="_blank" rel="noopener noreferrer">Register to hear our talk, and meet us during the virtual networking</a>. <img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712517684074-SPGPrints+%28Festival-APRIL-2024%29.jpg" style="width: 100%px;" class="fr-fic fr-dib"><hr>We have looked critically at this transition. Investments in Industrial-scale equipment, though substantial, ultimately leads to significant cost reductions in large-scale production. This is essential if manufacturers want to achieve sustainable, cost-effective printed electronics.Moreover, the transition to industrial-scale equipment like Rotary Screen Printing enhances repeatability and quality control. Lab-scale equipment often lacks the precision, required consistency and capacity for mass production. In contrast, industrial-scale tools offer robust control mechanisms, ensuring consistent output across large volumes. This shift results in higher product quality consistency, reducing defects and improving overall yield rates.A great example of a printed electronics application that is moving into high-volume industrialized scale are the printed e-paper displays by our partner Ynvisible. Their products are used on smart labels, IoT devices, retail signage and many more markets. Ynvisible even shares their know-how in scaling up printed electronics with other companies in the flexible solar and printable battery space.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712517725631-Img-1.jpg" style="width: 100%px;" class="fr-fic fr-dib">Printed ultra-low-power display for use in retailIf we take the e-paper example and run it through our break-even <a href="https://www.spgprints.com/printed-electronics-calculator?hsCtaTracking=35adfcbb-b27b-4123-9872-3bf81acad083%7Cda23b58a-7bd3-4c3a-99b7-2362dea12b57" rel="noreferrer noopener" target="_blank" data-hook="WebLink">calculator</a> you see that for a yearly production of 3.5 million screens the Rotary Screen Printing solution starts to become more profitable within 3 years of production. This shows that you need relatively high volumes to justify the investment in a full SPGPrints Rotary screen printing line, but it will pay off and will ensure steady profitable business in the long run. Of course SPGPrints also offers screen printing units that can be integrated into an existing or custom built line, changing the business case significantly. Next to owning the equipment SPGPrints (and our network of print service providers) offers Production-as-a-Service including application development consultancy.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712517753534-Img-2.jpg" style="width: 100%px;" class="fr-fic fr-dib">This is a calculation showing the cost per printed unit comparison between typical flat-bed screen printing and a full SPGPrints rotary screen printing line.It is imperative to acknowledge that transitioning equipment mid-development cycle extends the time to market. This delay arises from the need to recalibrate processes, optimize formulations, and adapt to the unique characteristics of industrial-scale equipment. This delay represents a critical trade-off, where time saved in large-scale production is weighed against the extended development phase.In conclusion, the transition from lab-scale and pilot equipment to industrial-scale production, like Rotary Screen Printing, plays a pivotal role in advancing printed electronics. While the cost reductions and enhanced repeatability are substantial benefits, it is important to recognize the inherent time-to-market trade-off associated with this transition. In this paper we will show some examples of how choosing for industrial-scale equipment at an early stage in development, saves time and money in the long run. Additionally, we will provide a calculation method to evaluate the most suitable production equipment for a specific application.Read more about our offerings online: <a href="https://www.spgprints.com/applications-printed-electronics" rel="noreferrer noopener" target="_blank" data-hook="WebLink">SPGPrints | Applications | Printed Electronics</a><hr><a href="https://www.techblick.com/exhibitors-2024-boston" rel="noreferrer noopener" target="_blank" data-hook="WebLink">We are exhibiting in Boston at the Future of Electronics RESHAPED</a>&nbsp;on 12-13 June 2024.&nbsp;<a href="https://www.techblick.com/electronicsreshapedusa" rel="noreferrer noopener" target="_blank" data-hook="WebLink">Register now and visit our booth</a>.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712517816523-SPG+Prints-Booth+Slide.jpg" style="width: 100%px;" class="fr-fic fr-dib">

Printed ultra low-power display for use in retail

Transitioning from Lab-scale in Printed Electronics: Going from lab and pilot equipment to rotary screen printing.  Learn about example applications in printed low-power displays for use in retail as well as cost-per unit calculation comparing flat-bed vs. rotary screen printing for mass production

Bridging the Divide: Transitioning from Lab-scale to Industrial-scale Equipment in Printed Electronics Development

Nvidia’s CUDA cores are specialized processing units within Nvidia graphics cards designed for handling complex parallel computations efficiently, making them pivotal in high-performance computing, gaming, and various graphics rendering applications.

Understanding Nvidia CUDA Cores: A Comprehensive Guide

Lights could soon use the full color suite of perfectly efficient organic light-emitting diodes, or OLEDs, that last tens of thousands of hours, thanks to an innovation from physicists and engineers at the University of Michigan.The U-M team’s new phosphorescent OLEDs, commonly referred to as PHOLEDs, can maintain 90% of the blue light intensity for 10-14 times longer than other designs that emit similar deep blue colors. That kind of lifespan could finally make blue PHOLEDs hardy enough to be commercially viable in lights that meet the Department of Energy’s 50,000-hour lifetime target. Without a stable blue PHOLED, OLED lights need to use less-efficient technology to create white light.The lifetime of the new blue PHOLEDs currently is only long enough to use as lighting, but the same design principle could be combined with other light-emitting materials to create blue PHOLEDs hardy enough for TVs, phone screens and computer monitors. Display screens with blue PHOLEDs could potentially increase a device’s battery life by 30%.“Achieving long-lived blue PHOLEDs has been a focus of the display and lighting industries for over 20 years. It is probably the most important and urgent challenge facing the field of organic electronics,” said <a href="https://eecs.engin.umich.edu/people/forrest-stephen-r/" target="_blank" rel="noreferrer noopener">Stephen Forrest</a>, the Peter A. Franken Distinguished University Professor of Electrical and Computer Engineering at the University of Michigan. He is also the corresponding author of the study published today in Nature.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1703720458568-Haonan-and-Claire-lab-1-1.jpg" style="width: 300px;" class="fr-fic fr-dib">Haonan Zhao and Claire Arneson, two doctoral students in physics and graduate student research assistants in electrical and computer engineering at the University of Michigan, fabricate their blue PHOLED devices in the lab. Their design prevents the excited molecules within the PHOLEDs light-emitting material from colliding, which could break the bonds holding the molecules together. Photo credit: Miranda Felty, University of MichiganPHOLEDs have nearly 100% internal quantum efficiency, meaning all of the electricity entering the device is used to create light. As a result, lights and display screens equipped with PHOLEDs can run brighter colors for longer periods of time with less power and carbon emissions.Before the U-M team’s research, the best blue PHOLEDs weren’t durable enough to be used in either lighting or displays. Only red and green PHOLEDs are stable enough to use in devices today, but blue is needed to complete the trio of colors in OLED “RGB” displays and white OLED lights. Red, green and blue light can be combined at different relative brightness to produce any color desired in display pixels and light panels.So far, the workaround in OLED displays has been to use older, fluorescent OLEDs to produce the blue colors, but the internal quantum efficiency of that technology is much lower. <a href="https://pubs.rsc.org/en/content/articlehtml/2023/tc/d3tc00245d" target="_blank" rel="noreferrer noopener">Only a quarter</a> of the electric current entering the fluorescent blue device produces light.“A lot of the display industry’s solutions are upgrades to fluorescent OLEDs, which is still an alternative solution,” said study first author Haonan Zhao, a doctoral student in physics and electrical and computer engineering. “I think a lot of companies would prefer to use blue PHOLEDs, if they had the choice.”To make blue light, electricity excites heavy metal-containing phosphorescent organic molecules. Sometimes, the excited molecules come into contact before emitting the light, transferring all of the pair’s stored energy into one molecule. Because the energy of blue light is so high, the transferred energy, which is double that of the single excited molecule, can break chemical bonds and degrade the organic material.One way around this problem is to use materials that emit a broader spectrum of colors, which lowers the total amount of energy in the excited states. But such materials appear cyan or even green, rather than a deep blue.The U-M team got around this issue by sandwiching cyan material between two mirrors. By perfectly tuning the space between the mirrors, only the deepest blue light waves can persist and eventually emit from the mirror chamber.Further tuning the optical properties of the organic, light-emitting layer to an adjacent metal electrode introduced a new quantum mechanical state called a plasmon-exciton-polariton, or PEP. This new state allows the organic material to emit light very fast, thus further decreasing the opportunity for excited states to collide and destroy the light-emitting material.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1703720495886-Haonan-and-Claire-lab-2-1.jpg" style="width: 300px;" class="fr-fic fr-dib">The research team constructs their blue PHOLEDs inside a glovebox that keeps the PHOLEDs away from oxygen and water before they are fully encased in nitrogen. It’s a standard procedure that protects the device’s sensitive optics and electronics. Photo credit: Miranda Felty, University of Michigan“In our device, the PEP is introduced because the excited states in the electron transporting material are synchronized with the light waves and the electron vibrations in the metal cathode,” said study co-author Claire Arneson, a doctoral student in physics and electrical and computer engineering.

Lights could soon use the full color suite of perfectly efficient organic light-emitting diodes, or OLEDs, that last tens of thousands of hours, thanks to an innovation from physicists and engineers at the University of Michigan.

Blue PHOLEDs: Final color of efficient OLEDs finally viable in lighting

In April 1981, The Washington Post&nbsp;reported that the U.S. supermarket chain, Giant Food Inc., was about to stop marking prices on individual items in its stores in a bid to reduce operating costs. If there was no consumer backlash, the report predicted, the rest of the industry would follow, as it did when the company was the first food retailer to introduce barcode scanners at its checkouts, spurring the spread of that technology across the country.Fast forward 40 years and individually priced items in supermarkets have long been consigned to history, with shelf pricing now the accepted norm. And it has, as Giant Food hoped, reduced operating costs for retailers that can stock as many as 50,000 different product lines. As recently as the 1990s, 7,000 product lines was considered average. Now technology is overhauling shelf labeling anew, and supermarkets will be the likely trailblazers once again.<h2>The beginning of the end for paper labels</h2>Electronic shelf labels (ESL) are connected, low-power &lsquo;e-paper&rsquo; display devices that can replace traditional paper labels and can display text, numbers, icons, lines, barcodes and pictures. They enable retailers to automatically update individual shelf price labels from a central point across multiple stores and branches&mdash;or in certain geographic locations&mdash;at the touch of a button. Comprised of a Cloud platform, access points or gateways, and wirelessly connected shelf labels, pricing commands can be sent from a web-based dashboard to store-located gateways, from which point commands are relayed to the smart labels.According to analyst ABI Research, by the end of last year, 788 million electronic shelf labels (ESL) had been installed globally. The number may seem significant, but with tens of billions of paper labels still on shelves, the technology has yet to make it mainstream, despite not really counting as a &lsquo;new&rsquo; technology. Primitive versions using liquid crystal displays that could display a price but nothing else have been around for some 30 years. There are a number of reasons the technology has yet to hit the big time, including market fragmentation, cost of deployment, concerns over interoperability, security, and a fear of obsolescence. Now this could be about to change.Earlier this year, the Bluetooth Special Interest Group (SIG), announced the release of the <a href="https://www.bluetooth.com/learn-about-bluetooth/use-cases/electronic-shelf-labels/?utm_campaign=2021%20wevolver" rel="noopener noreferrer" target="_blank">new wireless standard for the ESL market</a>, with the goal of making Bluetooth the standard protocol for ESL.&nbsp;The scalable, low-power, secure ESL standard (consisting of ESL Profile and Service specifications) has been developed by a working group comprised of a leading ESL vendor and enabling technology suppliers, and standardizes the process for message transmission between access points and ESLs. To do so it leverages feature enhancements introduced in the Bluetooth Core Specification Version 5.4, including Periodic Advertising with Responses (PAwR) and Encrypted Advertising Data (EAD).In general, PAwR and EAD are intended for one-to-many applications that involve a large number of devices (tags) receiving and transmitting small amounts of data from and to an access point, that accept longer latencies (e.g. 2 seconds) in exchange for extended battery life. Together, they enable connectionless, bidirectional, secure communication with thousands of very low-power end nodes in a star topology, essential in a retail ESL application where many thousands of labels could be required to cover all of the items stocked. For a technical deep dive on ESL, PAwR and EAD see <a href="https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/whats-new-in-bluetooth-v5-4-an-overview?utm_campaign=2021%20wevolver" rel="noopener noreferrer" target="_blank">What&#39;s new in Bluetooth v5.4: An overview</a>.<h2>Dynamic, efficient pricing operations</h2>If the introduction of the standard has the intended effect on the retail industry and ESL becomes widespread, retailers are set to benefit in several ways. Updating paper price labels requires staff to change thousands of tags every week. It&rsquo;s not only a lot of labor to do very little, it also takes time and is prone to error, and inaccurate pricing on shelves even for a short time can cost grocery retailers profit. ESL eliminates the manual process and at the same time enables dynamic pricing strategies allowing retailers to adjust pricing based on stock levels, demand, and market conditions.Standardization is key here to ensure interoperability, security and to allow retailers to have systems that can be installed and easily maintained over a long lifespan. At the same time, Bluetooth can also be leveraged to keep tags updated with the latest firmware, using Over-The-Air Device Firmware Updates from the gateway itself.Moreover, by using Bluetooth as the protocol, some ESL systems can mix and match with other Bluetooth technologies, such as Bluetooth Direction Finding for a quick positioning, enabling staff to quickly and easily identify the specific location of individual product lines across the store. This is particularly beneficial to staff responsible for picking and replenishing stock. Paired with Wi-Fi-connected shelf cameras and Cloud-based AI models, savvy retailers are also remotely monitoring stock to ensure shelves are well stocked and only replenished when necessary.The smart labels can also be used as beacons for marketing to consumers in close proximity via compatible smartphone apps, at the same time allowing retailers to gather insights into customer behavior to provide improved shopping experiences, personalized marketing, and to increase conversion rates in store.<h2>Widescale adoption looms</h2>Nordic Semiconductor, as the market leader in Bluetooth LE, has already introduced the PAwR and EAD features as standard in its qualified Bluetooth 5.4 SoftDevice Controller in the <a href="https://www.nordicsemi.com/Products/Development-software/nRF-Connect-SDK?utm_campaign=2021%20wevolver" rel="noopener noreferrer" target="_blank">nRF Connect SDK</a>, and companies developing ESLs can start working with this technology today thanks to the pre-release reference example (both gateway and tags) now available on request by opening a <a href="https://devzone.nordicsemi.com/support/add?utm_campaign=2021%20wevolver" rel="noopener noreferrer" target="_blank">private ticket on DevZone</a> or by <a href="https://www.nordicsemi.com/About-us/Contact-Us?utm_campaign=2021%20wevolver" rel="noopener noreferrer" target="_blank">contacting Nordic sales</a>.Nordic&rsquo;s SoCs meet the ultra low power requirements of ESLs where the number of tags involved prohibits even infrequent battery changes, while the Flash and RAM allocation ensures they can store the volume of information required to implement a fully-featured ESL system. Both the nRF53 Series and several of the nRF52 Series SoCs also support Direction Finding, enabling optimized order picking and replenishment functionality.The announcement of the standard has provided retailers with the impetus to commit to this technology. ABI Research claims 185 million ESL units were shipped last year, and that by 2028 annual shipments will reach 558 million, with a total installed base of some three billion ESLs. For example, Fortune 500 leading light and U.S. retail behemoth Walmart has entered an agreement to roll out 60 million digital shelf labels across 500 locations over the next 12 to 18 months. Others will follow.<hr>This article was first published on Nordic&#39;s <a href="https://blog.nordicsemi.com/getconnected" target="_blank" rel="nofollow" id="isPasted"></a><a href="https://blog.nordicsemi.com/getconnected?utm_campaign=2021%20wevolver" target="_blank" rel="nofollow">Get Connected Blog</a>. &nbsp;

Electronic shelf labels (ESL) are connected, low-power ‘e-paper’ display devices that can replace traditional paper labels and can display text, numbers, icons, lines, barcodes and pictures. They enable retailers to automatically update individual shelf price labels from a central point across multiple stores and branches—or in certain geographic locations—at the touch of a button.

Bluetooth Electronic Shelf Label standard heralds new retail dawn

In this episode, we discuss research from Harvard that tackles the blurriness and lack of disruption recovery with most holograms which prevents users from having an immersive experience.

Podcast: Key To Unlock Immersive Holograms

Build your digital signage solution to manage advertising displays with single-board computers.


Building Cost-Effective Advertising Displays with SBCs

Researchers have developed new technology that could usher in the &quot;next-generation&quot; of thinner, higher-resolution and more energy efficient screens and electronic devices. The international team from Nottingham Trent University in the United Kingdom, The Australian National University (ANU) and UNSW Canberra has&nbsp;created nanoparticles called &quot;metasurfaces&quot; that perform better than current displays like LCDs and LEDs. LCDs and LEDs rely on liquid crystal cells to create a display on TVs and other screens. The research team&#39;s metasurfaces are 100 times thinner than liquid crystal cells, offer a tenfold greater resolution and consume 50 per cent less energy. The researchers believe their technology is compatible with modern electronic displays. &quot;We have paved the way to break a technology barrier by replacing the liquid crystal layer in current displays with a metasurface, enabling us to make affordable flat screens liquid crystal-free,&quot; lead researcher Mohsen Rahmani, Professor of Engineering at Nottingham Trent University, said. &quot;The most important metrics of flat panel displays are pixel size and resolution, weight and power consumption. We have addressed each of these with our meta-display concept. &quot;Most importantly, our new technology can lead to a huge reduction of energy consumption - this is excellent news given the number of monitors and TV sets being used in households and businesses every single day. We believe it is time for LCD and LED displays to be phased out in the same way as former cathode ray tube (CRT) TVs over the past ten to 20 years.&quot; Dragomir Neshev, Director of the ARC Centre for Excellence in Transformative Meta-Optical Systems (TMOS) and ANU Professor in Physics, said: &quot;The capability of conventional displays has reached its peak and is unlikely to significantly improve in the future due to multiple limitations. &quot;Today there is a quest for fully solid-state flat display technology with a high-resolution and fast refresh rate. We have designed and developed metasurface pixels that can be ideal for the next-generation display. &quot;Unlike liquid crystals, our pixels do not require polarised lights for functioning, which will halve screens&#39; energy consumption.&quot; Khosro Zangeneh Kamali, a PhD scholar at ANU and the first author of the study, said: &quot;Metasurfaces are proven to exhibit extraordinary optical behaviour. &quot;However, inventing an effective way to control them is still a subject of heavy research. We have proposed electrically programmable silicon metasurfaces, which is a versatile platform for programmable metasurfaces.&quot;&nbsp; Dr Lei Xu, a team member from Nottingham Trent University, said: &quot;There is significant room for further improvements by employing artificial intelligence and machine learning techniques to design and realise even smaller, thinner and more efficient metasurface displays.&quot; Professor Andrey Miroshnichenko, a team member from UNSW Canberra, said: &quot;Our pixels are made of silicon, which offers a long lifespan in contrast with organic materials required for other existing alternatives. Moreover, silicon is widely available, CMOS compatible with mature technology, and cheap to produce.&quot; Professor Miroshnichenko said the team hoped their development could generate a frontier technology in new flat displays with a global market value of about $117 billion in 2020. The work is reported in the journal&nbsp;<a href="https://aus01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fanu.us2.list-manage.com%2Ftrack%2Fclick%3Fu%3D73b3c4bf45063d7aa04d62036%26id%3D7b14896d75%26e%3Da3d1be9eda&data=05%7C01%7Cjames.giggacher%40anu.edu.au%7C3aa53e73db6f43b787c308db15138a89%7Ce37d725cab5c46249ae5f0533e486437%7C0%7C0%7C638126945905851498%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=1XgS6ghU7I9hrvV%2BPDdflpeNRGWeOEOf4kRtvlLVivo%3D&reserved=0" target="_blank">Light: Science &amp; Applications</a>. &nbsp;

PhD scholar Khosro Zangeneh. Photo: Jamie Kidston/ANU

Researchers have developed new technology that could usher in the "next-generation" of thinner, higher-resolution and more energy efficient screens and electronic devices.

New tech could create cheaper and thinner flat screens

XTPL developed an unique an totally new approach of printing functional materials with unparallel precision and repeatability. Technology called Ultra-Precise Deposition (UPD) is a nanodispensing method capable to print high density and high viscous materials with the resolution down to 1 &micro;m in feature size and with high ratio of width to height after single pass. For this method material extrusion is controlled by a pressure, which means it is not supported with high electric field. Thanks to this there are no limitation if the substrate is conductive or dielectric.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjY3OTQ0NDk1MzczLUltZy0xLmpwZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 736px;" class="fr-fic fr-dib">The combination of unique parameters of the UPD approach opens new possibilities, previously not covered by any other printing methods. First of all, the resolution of the conductive traces can reach 1/1 &micro;m L/S. What is more, similar resolution can be achieved even on complex, 3D topographies. This enables printing high density interconnections through even 90&deg; steps (for example wire-bonding alternative for chip interconnections). Two more unique features were originally tested for conductive structures, but can have a huge benefit for printing other materials like QD ink. These features are micro-bumps deposition and via/micro-cavity filling with the highest repeatability comparing to other printing methods. The biggest needs for QD Color Conversion are ultra-high resolution, possibility of using high solid content inks for high efficiency and repeatability for high homogeneity of the display.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1667944549431-Img-2.jpg" style="width: 764px;" class="fr-fic fr-dib">The precise microdots deposition capability can be used for deposition of micro-bumps for flip chip application. Currently the results presented on the slide below are made using highly-concentrated silver paste (CL85). The dot diameter is around 8 &micro;m, and the dot height is around 800 nm, which gives a relatively high aspect ratio compared to printed electronics techniques, like inkjet or EHD, and competitive repeatability. The cross-section analysis of the dots shows parabolic geometry, which, for example, simplifies the deposition of subsequent layers without the risk of cracks. A photo of Albert Einstein made of hundreds of thousands of 8 &micro;m micro-bumps presents also the stability of the process over the time.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1667944610806-Img-3.jpg" style="width: 750px;" class="fr-fic fr-dib">The ability of UPD to extrude ink with femtoliter precision allows not only to print microdots but also to fill microcavities. This feature may help manufacture high-resolution multilayers or through silicon via interconnections. To fill a microcavity, one has to precisely position the printing nozzle and dispense a certain amount of material. In the slide below you can see microcavity with a depth of 10 &mu;m and a diameter of 25 &mu;m, which we uniformly fill with a silver paste (85 wt.% of solid content). Similar capabilities of precise microcavity filling can be used in deposition of QD material into structures like photoresist windows or nanorings to significantly increase color conversion efficiency (CCE). Compared to other digital additive manufacturing techniques like inkjet and EHD, UPD technology allows to fill the structures with high uniformity and repeatability with use of inks with higher concentration of QDs. Combination of unique capabilities of the UPD printing method provides a solution for efficient fabrication of QD color conversion for next generation Micro-LED displays.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1667944645211-Img-4.jpg" style="width: 751px;" class="fr-fic fr-dib">

A unique new approach of printing functional materials with unparallel precision and repeatability. Technology called Ultra-Precise Deposition (UPD) is a nanodispensing method capable to print high density and high viscous materials with the resolution down to 1 µm in feature size and with high ratio of width to height after single pass. For this method material extrusion is controlled by a pressure, which means it is not supported with high electric field. Thanks to this there are no limitation if the substrate is conductive or dielectric.

Ultra-Precise Deposition for the Fabrication of Next-Generation MicroLED and QD-LED Displays

Building on their groundbreaking work for <a href="file:///Users/cmsj/Downloads/for%20any%20display%20or%20VR%20application.%2010:42:28%20You%20need%20to%20have%203%20colors,%20red,%20green,%20and%20blue,%20so%20so%20very%20important%20to%20have%20them,%20and%20also%20very%20important%20to%20have%20a%20stable%20emission.%2010:42:39%20So%20that,%20you%20know,%20when%20your%20display%20becomes%20brighter.%2010:42:42%20You%20have%20seen%20the%20same%20color%20right%3f%20if%20it's%20not%20stable%20when%20you%20increase%20the%20brightness,%20then%20the%20green%20becomes%20the%20bluish,%20red%20of%20it%20becomes%20greenish,%20so%20it's%20not%20a%20high%20quality%20display.%2010:42:57%20And%20so%20what's%20really%20important%20here%20is%20a%20way%20to%20make%20them%20very,%20very%20stable%20for%20such%20a%20small%20size%20LEDs,%20and%20be%20able%20to%20grow%20them%20directly%20on%20the%20silicon%20wave,%20which%20is%20really%20really%20important%20for%20the%20future%20manufacturing%2010:43:10%20integration%20process" target="_blank">highly-efficient red micro light emitting diodes (LEDs),&nbsp;</a>Prof. Zetian Mi&rsquo;s research team have now achieved a new approach for the design, fabrication, and integration of high-performance green micro-LEDs on silicon. These highly stable micro-LEDs are important for a broad range of applications in on-chip optical communication, including emerging augmented reality/mixed reality devices, and ultrahigh-resolution full-color displays.&ldquo;It&rsquo;s very important to have a stable emission of all three colors &ndash; red, green, and blue &ndash; to achieve a high-quality display,&rdquo; Mi said. &ldquo;And it&rsquo;s especially important to grow these small, stable LEDs directly on the silicon wafer for the future manufacturing and integration process.&rdquo;LEDs, which are typically stacks of semiconductor thin films, have already revolutionized the lighting and display world. They are far superior in efficiency, stability, and device volume compared to traditional devices, such as incandescent light bulbs and cathode tubes.However, LEDs have many limitations when it comes to supporting virtual and augmented reality, as well as other emerging optoelectronic applications. These new applications demand micrometer or smaller LEDs that are highly stable, highly efficient, have ultralow power consumption, and can support full-color emission and brightness. In other words, they need to be one million times smaller than conventional broad area devices without sacrificing their quality.Mi&rsquo;s team recently succeeded in creating red micro-LEDs that are nearly three orders of magnitude smaller in surface area than previously reported devices while exhibiting external quantum efficiency of ~1.2%, but green micro-LEDs come with their own challenges.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1666235664577-pandey-malhotra-1024x332.jpg" style="width: 766px;" class="fr-fic fr-dib">Mi&rsquo;s red micro-LED research: (L) Postdoctoral researcher Ayush Pandey helped plan the parameters of the nanowires for growth in the MBE system, and then fabricated the actual LEDs in the Lurie Nanofabrication Facility. (R) ECE doctoral student Yakshita Malhotra helped plan the parameters and then grow the nanowire crystals using the MBE system in Prof. Mi&rsquo;s lab.&nbsp;&ldquo;You can make very efficient large-area blue LEDs and large area red LEDs, but it is extremely difficult to make very efficient large area green LEDs. This is called the &lsquo;Green Gap,&rsquo;&rdquo; Mi said. &ldquo;But shrinking a device&rsquo;s dimension to about one micrometer is extremely challenging whether it&rsquo;s green or red.&rdquo;In addition, it&rsquo;s important for these micro- and submicron-LEDs to be grown on silicon, instead of the traditional sapphire wafer. Silicon wafers improve the manufacturing process, allow for improved scalability and integration with small electronics, and are more cost-efficient. Specifically, they&rsquo;re more suitable for integration with complementary metal-oxide-semiconductor (CMOS) electronics, which would pave the way for much more powerful photonic circuits. But using silicon also creates a mismatch in the lattice parameter, for the crystal structure is different.To address these challenges, Mi&rsquo;s team developed III-nitride submicron-scale green micro-LEDs using arrays of nanowires, each of which is only 100-200 nm in diameter and tens of nanometers apart.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1666235687610-GreenLED-content.jpg" style="width: 766px;" class="fr-fic fr-dib">Yixin Xiao, center, a PhD student, and Yuanpeng Wu, a postdoctoral research fellow, both in ECE, and members of Professor Zetian Mi&rsquo;s research group, working in the molecular beam epitaxy lab in the EECS Building on the North Campus of the University of Michigan. In the lab they are growing Indium gallium nitride (InGaN) nanowire micro-LEDs using molecular beam epitaxy. Photo: Brenda Ahearn/College of Engineering&nbsp;&ldquo;We use the nanowire structure to filter out the threading dislocations caused by lattice mismatch between the nitride materials and the silicon substrate,&rdquo; said Yuanpeng Wu, a postdoc in Mi&rsquo;s group and first author on the paper.The result is the first high-performance, highly stable green micro-LEDs grown on silicon. They plan to apply the same sort of process for blue micro-LEDs.&ldquo;The approach we developed for green readily applies to blue,&rdquo; Mi said. &ldquo;The next step is integrating directly on the silicon wafer without transferring, which would be a huge improvement for manufacturing.&rdquo;With red, green, and blue micro-LEDs, the future of next-generation display technology begins.The research is detailed in&nbsp;<a href="https://trebuchet.public.springernature.app/get_content/f868891b-9374-4648-bd01-13235847ca08" target="_blank">&ldquo;InGaN micro-light-emitting diodes monolithically grown on Si: achieving ultra-stable operation through polarization and strain engineering&rdquo;</a> by Yuanpeng Wu, Yixin Xiao, Ishtiaque Navid, Kai Sun, Yakshita Malhotra, Ping Wang, Ding Wang, Yuanxiang Xu, Ayush Pandey, Maddaka Reddeppa, Walter Shin, Jiangnan Liu, Jungwook Min, and Zetian Mi,&nbsp;Light Science &amp; Application,&nbsp;October 2022.Fabrication work was accomplished in the&nbsp;<a href="https://lnf.umich.edu/" target="_blank">Lurie Nanofabrication Facility,</a> and technical support was provided by the&nbsp;<a href="https://mc2.engin.umich.edu/" target="_blank">Michigan Center for Materials Characterization</a>.Some intellectual property related to GaN-based nanowires was licensed to NS Nanotech Inc., which was co-founded by Mi. The University of Michigan and Mi have a financial interest in NS Nanotech, Inc.

Yuanpeng Wu, right, a postdoctoral research fellow, and Yixin Xiao, a PhD student, both in ECE, and members of Professor Zetian Mi’s research group, working in the molecular beam epitaxy lab in the EECS Building on the North Campus of the University of Michigan. In the lab they are growing Indium gallium nitride (InGaN) nanowire micro-LEDs using molecular beam epitaxy. Photo: Brenda Ahearn/College of Engineering

Prof. Zetian Mi’s team are the first to achieve high-performance, highly stable green micro-LEDs with dimensions less than 1 micrometer on silicon, which can support ultrahigh-resolution full-color displays and other applications.

Breakthrough in green micro-LEDs for augmented-mixed reality devices

As anyone who has recently tried out an augmented reality headset knows, the technology is not yet ready to be part of our everyday lives. Researchers have been working to perfect high-performing augmented reality (AR) glasses, but there are a number of challenges. One major problem with conventional AR glasses is that there is a tradeoff in terms of quality and brightness between the external scene you actually see and the contextual information you also want to visualize. Early solutions like Google Glass used multiple bulky optical components that were partially reflective and partially transmissive to mix the real-world and contextual scenes, with the result of a dimmed and distorted vision of both scenes.More recent AR head-mounted-display eyeglasses have been patterned with diffractive gratings (fine grooves) with wavelength-sized spacing that deflect contextual information from a miniprojector beside the glasses to the viewer&rsquo;s eye. But these eyeglasses still dim and distort the external scene because real-world light passing through the glass inevitably gets scattered and dispersed by the gratings. The distortions get worse when several sets of overlapping gratings must be used to handle multiple distinct colors from the miniprojector. AR glasses that perfectly blend the external environment and contextual information for the human eye would be highly useful for many applications. As a head-up display, the technology could give navigation instructions to someone driving a car or feed data from sensors to the pilot flying a plane without requiring them to look away from their windshields. As a head-mounted display, the technology could enable surgeons and soldiers to view information related to their tasks at hand with unprecedented ease and efficiency.The glass needs to not only be highly transparent over almost the entire visible spectrum, allowing for unattenuated and undistorted vision of the outside world, but also to function as a highly efficient lens that focuses light from a miniprojector into the human eye to form a visual context accompanying the external real-world scene.<h2>Study demonstrates new kind of wavelength-selective, wavefront-shaping glass<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1664972880052-multifunctional-nonlocal-metasurface-enabled-ar-demonstration.jpg" style="width: 766px;" class="fr-fic fr-dib">Illustration showing the operation of an augmented reality headset with multifunctional nonlocal metasurfaces as optical see-through lenses. Credit: Nanfang Yu, Stephanie Malek, Adam Overvig/Columbia Engineering&nbsp;</h2><section id="isPasted">Researchers at <a href="http://engineering.columbia.edu/" target="_blank">Columbia Engineering</a> report that they have now invented just this kind of glass. Led by <a href="https://www.engineering.columbia.edu/faculty/nanfang-yu" target="_blank">Nanfang Yu</a>, associate professor of <a href="https://www.apam.columbia.edu/" target="_blank">applied physics and applied mathematics</a>, the team has created a flat optical device that focuses only a few selected narrowband colors of light while remaining transparent to nonselected light over the vast majority of the spectrum. The <a href="https://www.nature.com/articles/s41377-022-00905-6" target="_blank">paper</a> was published online August 8, 2022, by Light: Science &amp; Applications.</section><section><blockquote>We&rsquo;ve built a very cool flat optical device that appears entirely transparent&mdash;like a simple piece of glass&mdash;until you shine a beam of light with the correct wavelength onto it, when the device suddenly turns into a lens. To me this is optical magic.<footer>NANFANG YUASSOCIATE PROFESSOR OF APPLIED PHYSICS AND APPLIED MATHEMATICS</footer></blockquote></section><section>&ldquo;We&rsquo;ve built a very cool flat optical device that appears entirely transparent&mdash;like a simple piece of glass&mdash;until you shine a beam of light with the correct wavelength onto it, when the device suddenly turns into a lens,&rdquo; said Yu, a leader in nanophotonics research. &ldquo;To me this is optical magic.&rdquo;<h2>Metasurfaces</h2></section><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1664972967719-flat-glass-visual.jpg" style="width: 766px;" class="fr-fic fr-dib">Top row: (Left) Illustration showing the operation of a wavelength-selective metalens, with &ldquo;green&rdquo; light being focused, while the other colors are passed without distortion. (Middle) Optical image of a wavelength-selective metalens composed of rectangular apertures etched into a silicon thin film. (Right) Scanning electron microscope (SEM) images of the metalens at its center and edge.&nbsp; Bottom row: A series of two-dimensional (2D) far-field scans shows that focusing is most efficient at the center of the resonance, l= 1590 nm, with the focusing efficiency dropping at the two shoulders of the resonance, l= 1575 nm and 1600 nm, and that the focal spots become almost undetectable at wavelengths tens of nanometers away from the center of the resonance. Credit: Nanfang Yu, Stephanie Malek, Adam Overvig/Columbia Engineering&nbsp;<a href="https://www.apam.columbia.edu/faculty/nanfang-yu" target="_blank">Yu&rsquo;s group</a> develops flat optical devices based on metasurfaces&mdash;ultra-thin optical components&mdash;to control light propagation in free space and in optical waveguides. Metasurfaces are made of two-dimensional (2D) arrays of designer scatterers, called &ldquo;optical antennas&rdquo; &mdash; a tiny version of radio antennas that have nanometer-scale dimensions. The key feature of metasurfaces is that the optical scatterers are all different optically. The light they scatter can have different amplitude, phase, or polarization, so that metasurfaces can introduce a spatially varying optical response that can control light in extremely flexible ways. As a result, metasurfaces make it possible to realize functionalities that conventionally require 3D optical components or devices with a much larger footprint, such as focusing or steering light beams, or switching optical signals on integrated photonic chips.<h2>Nonlocal metasurfaces</h2>Yu&rsquo;s team invented a &ldquo;nonlocal metasurface&rdquo; that can manipulate light waves in distinct ways at distinct targeted wavelengths, while leaving light at untargeted wavelengths unaffected. The new devices exert both spatial and spectral control over light by selecting a color (spectral) and focusing it (spatial) not just at a single wavelength but also independently at multiple different wavelengths. For example, one demonstrated device functions both as a converging lens that focuses light at one color, and as a concave lens that disperses light at a second color, while staying transparent, like an unpatterned slab of glass, when illuminated with light at colors over the rest of the spectrum.<h2>Breaking symmetry to radiate light and shape its wavefront</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1664972997562-flat-glass-visual2.jpg" style="width: 766px;" class="fr-fic fr-dib">Left: Illustration showing the operation of a three-function metalens doublet. The doublet is able to generate three distinct focal patterns (two focal lines orthogonal to each other and a star-shaped focal spot) at three different wavelengths, while staying transparent at other wavelengths. The doublet is composed of a quasi-radial metalens as a diverging element and a dual-function cylindrical metalens as a converging element. Middle: Optical images of the quasi-radial metalens and the dual-function cylindrical metalens. Right: SEM images showing the corners of the quasi-radial metalens and the dual-function cylindrical metalens. Credit: Nanfang Yu, Stephanie Malek, Adam Overvig/Columbia Engineering&nbsp;These new devices originated from theoretical explorations by Adam Overvig, a former PhD student in Yu&rsquo;s group and co-author of the study, into how to manipulate symmetry in photonic crystal (PhC) slabs, such as a 2D periodic structure that is a square array of square holes defined in a thin film of silicon. PhC slabs are known to support a set of modes, the frequencies or colors of which are determined by the geometry of the slab (e.g., periodicity of the array and size of the holes). The modes are essentially a sheet of light that is spatially extended (nonlocal) along the slab but otherwise confined in the direction normal to the slab.Introducing a symmetry-breaking perturbation to an otherwise structurally repetitive PhC slab, such as simply by deforming square holes of the PhC into rectangular ones, lowers the degree of symmetry of the PhC so that the modes are no longer confined to the slab: they can be excited by shining a beam of light from free space with the correct color and can also radiate back into free space.Significantly, instead of applying a uniform perturbation over the entire PhC slab, the researchers spatially varied the perturbation, orienting the rectangular holes along different directions over the device. In this way, the surface emission from the device could have a molded wavefront in relation to the pattern of the orientation angles of the rectangles.<h2>First to make lenses that focus light of just the desired color</h2>&ldquo;This is the first time that anyone has experimentally demonstrated wavelength-selective, wavefront-shaping optical devices using an approach that is based on symmetry-breaking perturbations,&rdquo; explained Stephanie Malek, a doctoral student in Yu&rsquo;s group who was lead author of the study. &ldquo;By carefully choosing the initial PhC geometry, we can achieve wavelength selectivity, and by tailoring the orientations of the perturbation applied to the PhC, we can sculpt the wavefront of the selected color of light. This means that we can make lenses that focus light of only the selected color.&rdquo;<h2>The most highly multifunctional and multicolor metasurface yet</h2>The team demonstrated a multifunctional device that shapes the optical wavefronts independently at four distinct wavelengths but acts as a transparent substrate at other nonselected wavelengths. This makes it the most highly multifunctional and multicolor metasurface that has been demonstrated so far, and also suggests that in the future full-color AR displays can be made by independently controlling a few colors of virtual information.<h2>AR applications</h2>These new wavelength-selective, wavefront-shaping &ldquo;nonlocal&rdquo; metasurfaces offer a promising solution for AR technologies, including head-up displays on the front windshield of cars. The optical see-through lens can reflect contextual information to the viewer&rsquo;s eye at selected narrow-band wavelengths of the miniprojector while also allowing an unobstructed, undimmed, broadband view of the real world. And, because the wavelength-selective metasurface lenses are thinner than a human hair, they are well-suited to developing AR goggles that look and feel like comfortable and fashionable eyeglasses.<h2>Quantum optics</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1664973027349-flat-glass-visual3.jpg" style="width: 766px;" class="fr-fic fr-dib">A series of 2D far-field scans showing the three focal patterns at l=1,424 nm, 1,492 nm, and 1,626 nm and minimal wavefront shaping over the rest of the spectrum. Credit: Nanfang Yu, Stephanie Malek, Adam Overvig/Columbia Engineering&nbsp;Yu&rsquo;s flat metasurfaces can also be used to substantially reduce the complexity of quantum optics setups that manipulate ultracold atoms. Because multiple laser beams at distinct wavelengths have to be independently controlled for cooling, trapping, and monitoring cold atoms, these setups can become massive. This complexity has made it difficult for researchers to widely adopt cold atoms for use in atomic clocks, quantum simulations and computations. Now, instead of building several ports around the vacuum chamber for the cold atoms, each with their unique beam-shaping optical components, a single metasurface device can be used to simultaneously shape the multiple laser beams used in the experiment.<h2>What&rsquo;s next: demonstrating the concept in visible spectrum range</h2>The devices in this study simultaneously and independently control the wavefronts of several near-infrared beams using nanostructured silicon thin films. The team plans next to demonstrate the concept in the visible spectral range, to fully control the wavefronts of three narrowband visible laser beams using a device platform featuring low absorption loss in the visible, such as thin-film silicon nitride and titanium dioxide. They are also exploring the scalability of the wavelength-selective metasurface platform by including more than two perturbations into a single metasurface and by stacking more than two metasurfaces into a compound device.Device fabrication was carried out at the <a href="http://cni.columbia.edu/" target="_blank">Columbia Nano Initiative</a> cleanroom, and at the <a href="https://asrc.gc.cuny.edu/nanofab/" target="_blank">Advanced Science Research Center NanoFabrication Facility</a> at the Graduate Center of the City University of New York.

Columbia engineers invent a flat lens that exclusively focuses light of a selected color—it appears entirely transparent until they shine a beam of light with the correct wavelength onto it, when the glass turns into a lens.

Optical Magic: New Flat Glass Enables Optimal Visual Quality for Augmented Reality Goggles

The researchers, from the Department&#39;s <a href="https://ee.eng.cam.ac.uk/" target="_blank">Electrical Engineering division</a>, designed the <a href="https://www.nature.com/articles/s41467-022-31853-9" target="_blank">next-generation smart lighting system</a> using a combination of nanotechnology, colour science, advanced computational methods, electronics and a unique fabrication process.They found that by using more than the three primary lighting colours used in typical LEDs, they were able to reproduce daylight more accurately. Early tests of the new design showed excellent colour rendering, a wider operating range than current smart lighting technology, and wider spectrum of white light customisation.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1664766264335-quantum-dots-copy_0.jpg" style="width: 766px;" class="fr-fic fr-dib">As the availability and characteristics of ambient light are connected with wellbeing, the widespread availability of smart lighting systems can have a positive effect on human health since these systems can respond to individual mood. Smart lighting can also respond to circadian rhythms, which regulate the daily sleep-wake cycle, so that light is reddish-white in the morning and evening, and bluish-white during the day.When a room has sufficient natural or artificial light, good glare control, and views of the outdoors, it is said to have good levels of visual comfort. In indoor environments under artificial light, visual comfort depends on how accurately colours are rendered. Since the colour of objects is determined by illumination, smart white lighting needs to be able to accurately express the colour of surrounding objects. Current technology achieves this by using three different colours of light simultaneously.Quantum dots have been studied and developed as light sources since the 1990s, due to their high colour tunability and colour purity. Due their unique optoelectronic properties, they show excellent colour performance in both wide colour controllability and high colour rendering capability.The Cambridge researchers developed an architecture for quantum-dot light-emitting diodes (QD-LED) based next-generation smart white lighting. They combined system-level colour optimisation, device-level optoelectronic simulation, and material-level parameter extraction.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1664766274411-3d.jpeg" style="width: 766px;" class="fr-fic fr-dib">TEM images of the red, green, cyan, and blue QDs used for device fabrication and charge transport simulation.The researchers produced a computational design framework from a colour optimisation algorithm used for neural networks in machine learning, together with a new method for charge transport and light emission modelling.The QD-LED system uses multiple primary colours &ndash; beyond the commonly used red, green and blue &ndash; to more accurately mimic white light. By choosing quantum dots of a specific size &ndash; between three and 30 nanometres in diameter &ndash; the researchers were able to overcome some of the practical limitations of LEDs and achieve the emission wavelengths they needed to test their predictions.The team then validated their design by creating a new device architecture of QD-LED based white lighting. The test showed excellent colour rendering, a wider operating range than current technology, and a wide spectrum of white light shade customisation.The Cambridge-developed QD-LED system showed a correlated colour temperature (CCT) range from 2243K (reddish) to 9207K (bright midday sun), compared with current LED-based smart lights which have a CCT between 2200K and 6500K. The colour rendering index (CRI) &ndash; a measure of colours illuminated by the light in comparison to daylight (CRI=100) &ndash; of the QD-LED system was 97, compared to current smart bulb ranges, which are between 80 and 91.The design could pave the way to more efficient, more accurate smart lighting. In an LED smart bulb, the three LEDs must be controlled individually to achieve a given colour. In the QD-LED system, all the quantum dots are driven by a single common control voltage to achieve the full colour temperature range.&ldquo;This is a world-first: a fully optimised, high-performance quantum-dot-based smart white lighting system,&rdquo; said <a href="http://www.eng.cam.ac.uk/profiles/jmk71" target="_blank">Professor Jong Min Kim</a> from Cambridge&rsquo;s Department of Engineering, who co-led the research. &ldquo;This is the first milestone toward the full exploitation of quantum-dot-based smart white lighting for daily applications.&rdquo;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1664766304130-4l.jpeg" style="width: 766px;" class="fr-fic fr-dib">Voltage-dependent chromaticity variations of the fabricated lighting systems with identical (green dots) and optimised (blue dots) emission pattern widths.&ldquo;The ability to better reproduce daylight through its varying colour spectrum dynamically in a single light is what we aimed for,&rdquo; said <a href="http://www.eng.cam.ac.uk/profiles/gaja1" target="_blank">Professor Gehan Amaratunga</a>, who co-led the research. &ldquo;We achieved it in a new way through using quantum dots. This research opens the way for a wide variety of new human responsive lighting environments.&rdquo;The structure of the QD-LED white lighting developed by the Cambridge team is scalable to large area lighting surfaces, as it is made with a printing process and its control and drive is similar to that in a display. With standard point source LEDs requiring individual control this is a more complex task.

Researchers have designed smart, colour-controllable white light devices from quantum dots, tiny semiconductors just a few billionths of a metre in size, which are more efficient and have better colour saturation than standard LEDs, and can dynamically reproduce daylight conditions in a single light