<html><head></head><body>Ultrafine line screen printing: emerging application and competing technologiesTechBlick - the home of additive electronics- &nbsp;prepared this presentation to outline the latest trends in ultrafine line screen printing as well as an overview of other ultrafine printing technologies. To be more specific, in the following video, you can see the following<ul><li>Existing and emerging applications for ever finer Screen Printing linewidths (sub-15 micron meters):&nbsp;Photovoltaic metallization | MicroLED wrap-around edge electrodes | Fan-out structure for flexible hybrid electronics | Transparent HMIs |Transparent Touch Displays | Edge Electrodes | MLCC | LTCC</li></ul> <ul><li>Hybrid and direct (non-digital) printing technologies towards sub-micron linewidths:&nbsp;Hybrid screen printing (print + etch/ablate) | R2R flexo printing | R2R Gravure Offset Printing &nbsp;|S2S Offset Printing | S2S Reverse Offset Printing |R2R Reverse Offset Printing | R2R Imprinting + Filling | R2R Photolithgraphy&nbsp;</li></ul>You can download the slides and read the full transcription of the presentaiton&nbsp;<a href="https://www.techblick.com/blog" target="_blank">here.</a><iframe width="640" height="360" src="https://player.vimeo.com/video/730919566" frameborder="0" allowfullscreen="" class="fr-draggable" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true"></iframe> </body></html>

We first discuss emerging and existing applications for ultra fineline screen printing, outlining how evolution of screen printing can unlock various electronic applications. Next, it will review other printing technologies extending the linewidth resolution to sub-micron range

Ultra fineline printed electronics: review of applications and technologies

The ability to maintain complex shapes without consuming power while flexible to go between multiple states is usually uncommon in a single material system. Shape morphing materials with adjustable rigidity have become a key element of several technological breakthroughs, from soft robotics to multimodal vehicles. To design a material system with the above-mentioned abilities, the technique of incorporating Japanese artistic geometric shapes, cuts (kirigami) and folds (origami) on a flat sheet can result in 3D output shapes under deformation. These types of materials are called mechanical metamaterials that allow a greater degree of freedom and extensibility– but are limited due to reconfigurability and reversibility of such systems. Another method for developing shape morphing systems is to control material properties across the sheet which can be achieved by adjusting deformation through heterogeneous material stiffness. However, this shape expansion at different locations in the material requires continuous external stimuli– indicating that shape morphing cannot be achieved without constant applied stimuli or energy inputs.&nbsp;A <a href="https://vtx.vt.edu/articles/2022/02/eng-bartlett-morphing-drone.html" target="_blank">group of researchers</a> affiliated with Macromolecules Innovation Institute and Department of Mechanical Engineering, Soft Materials and Structures Lab at Virginia Tech introduced a shape and rigidity morphing material that possesses capabilities like reversible and rapid polymorphic 3D reconfigurability and programmable stiffness [1]. Funded through Bartlett’s DARPA Young Faculty Award and Director’s Fellowship, the project led by Michael Bartlett, assistant professor in mechanical engineering explains, “when we started the project, we wanted a material that could do three things: change shape, hold that shape, and then return to the original configuration, and to do this over many cycles. One of the challenges was to create a material that was soft enough to dramatically change shape, yet rigid enough to create adaptable machines that can perform different functions.”<h2 dir="ltr">Shape-morphing mechanical metamaterial</h2>Interestingly, the introduced shape-morphing mechanical metamaterial can rapidly morph into load-bearing shapes in less than 0.1 seconds while still maintaining the shape and stiffness reconfigurability. To attain the state of this mechanical metamaterial, the team created a kirigami composite metamaterial sheet that features shape morphing by nonlinear deformation of elastomeric kirigami architecture and shape fixing by the nonlinear material response from plasticity and phase change of the embedded low-melting-point alloy (LMPA). The composite material consists of an endoskeleton made up of an LMPA, an embedded heating layer and an elastomeric kirigami encapsulation. The LMPA is Field’s metal that is a homogenous mixture of bismuth, indium and tin that can change from a high elastic modulus solid to a flowable liquid at a low melting temperature of 62°C.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1646518855656-Shape+morphing+mechanical+metamaterial.png" style="width: 800px;" class="fr-fic fr-dib">Shape and rigidity morphing mechanical metamaterial structure [Image Source: Research Paper]&nbsp;<div style='pointer-events: none; overflow: hidden; padding-bottom: 2px; z-index: auto; position: absolute; left: 0px; top: 512.162px; height: 39px; width: 766px; font-style: normal; font-variant: normal; font-weight: 400; font-stretch: 100%; font-size: 14px; font-family: "PT Serif", serif; text-align: center; text-transform: none; letter-spacing: normal; word-spacing: 0px; tab-size: 8;'> </div>“These composites have a metal endoskeleton embedded into rubber with soft heaters, where the kirigami-inspired cuts define an array of metal beams. These cuts combined with the unique properties of the materials were really important to morph, fix into shape rapidly, then return to the original shape,” Hwang said.Demonstrating the nonlinear force-extension characteristic, elastomeric kirigami architecture is capable of retaining high shapes during shape fixing in different configurations allowing high extensibility at minimum restoring force. The low-melting-point alloy exhibits material nonlinearities for shape morphing and can deform plastically at low strains– leveraging this to morph the material into load-bearing shapes. The shape of the material is reversible with the introduction of embedded heaters to melt the LMPA allowing the elastomeric kirigami architecture to reverse the plasticity and gain reconfigurability. The Gaussian curvature map (D) shows the negative and position region signifying the curved surface with complex curvature. The mechanical metamaterial overcomes the trade-offs between extensibility and load-bearing capability in a soft system– leading to the design of a functional morphing drone.<h2 dir="ltr">Soft robotic morphing drone</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1646518874395-Soft+robotic+morphing+drone.png" style="width: 800px;" class="fr-fic fr-dib">Soft robotic drone system with onboard components' list [Image Source: Research Paper]&nbsp;<div style='pointer-events: none; overflow: hidden; padding-bottom: 2px; z-index: auto; position: absolute; left: 0px; top: 450.838px; height: 39px; width: 766px; font-style: normal; font-variant: normal; font-weight: 400; font-stretch: 100%; font-size: 14px; font-family: "PT Serif", serif; text-align: center; text-transform: none; letter-spacing: normal; word-spacing: 0px; tab-size: 8;'> </div>To evaluate the application of the proposed mechanical metamaterial, the group designed a soft robotic morphing drone integrated with onboard power, control, motors and embedded heaters. Thanks to the autonomous morphing from ground to air vehicle configuration enabling multiple remotely controlled locomotion modes– can be deployed to collect cargo through water propulsion and buoyancy control. The embedded heaters in the soft robotic drone help it shape and morph to enable autonomous transformation from driving state to flying state. The transition from driving in state 1 to air vehicle configuration in state 2 is possible because of the contact between copper wires on the drone and liquid metal layers deposited on a power transfer station that enabled transformation to occur with no external intervention.&nbsp;“We’re excited about the opportunities this material presents for multifunctional robots. These composites are strong enough to withstand the forces from motors or propulsion systems, yet can readily shape morphs, which allows machines to adapt to their environment,” said Barron.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1646519066104-Morphing+and+deployable+underwater+machine.png" style="width: 800px;" class="fr-fic fr-dib" alt="Morphing and deployable underwater machine">Morphing and deployable underwater machine [Image Source: Research Paper]<div style='pointer-events: none; overflow: hidden; padding-bottom: 2px; z-index: auto; position: absolute; left: 0px; top: 351.45px; height: 39px; width: 766px; font-style: normal; font-variant: normal; font-weight: 400; font-stretch: 100%; font-size: 14px; font-family: "PT Serif", serif; text-align: center; text-transform: none; letter-spacing: normal; word-spacing: 0px; tab-size: 8;'> </div>Employing kirigami composites to develop a deployable underwater machine that starts in a flat shape which is then sequentially morphed into a swimming state to interact with the environment for collecting cargo. After performing the task, the material is retracted into the original flat shape. “The underwater machine consists of multiple stacked layers, including morphing kirigami composites with embedded liquid metal heaters, inflatable pneumatic membranes, and water propulsion channels,” the team notes. The bottom layer is designed to collect cargo while the top layer controls buoyancy for locomotion. This implementation shows the reversible deployability of morphing kirigami structures into different functional applications.The research article titled, “Shape morphing mechanical metamaterials through reversible plasticity is published in ScienceRobotics journal under <a href="https://www.science.org/doi/10.1126/scirobotics.abg2171" target="_blank">closed-access terms</a>. In the supplementary materials, the team has <a href="https://www.science.org/doi/suppl/10.1126/scirobotics.abg2171/suppl_file/scirobotics.abg2171_movies_s1_to_s4.zip" target="_blank">provided videos</a> on the implementation of the soft robotic drone, changing its shape reversibly.&nbsp;<h2 dir="ltr">References</h2>[1] D. Hwang, E. J. Barron, A. B. Haque, and M. D. Bartlett, “Shape morphing mechanical metamaterials through reversible plasticity,” Science Robotics, vol. 7, no. 63, 2022.&nbsp;

The researchers holding a piece of material that has been warped [Image Source: Virgnia Tech Blog]

Multifunctional shape-morphing material with reversible
and rapid polymorphic reconfigurability implemented into a soft robotic morphing drone that autonomously transforms from ground to air vehicle and an underwater morphing machine.

New soft robotic drone from a shape and rigidity morphing mechanical metamaterial

This article is a part of our <a href="http://www.wevolver.com/student-program" target="_blank">University Technology Exposure Program</a>. The program aims to recognize and reward innovation from engineering students and researchers across the globe.&nbsp;When we think of smart fabrics, we usually associate them with wearable and fashion technology, such as clothing that can track your health and physical activity or gloves that can sense tactile information or your finger gestures. Since textiles are ubiquitous in our environments, other realms of textiles, such as flooring and upholstery, will also benefit from functional materials augmentation and technological integration.&nbsp;MIT Media Lab researchers have developed a large-scale seamless interactive carpet and established an interdisciplinary project that unites new materials, sensing technologies, and advanced digital fabrication with contemporary dance and music. Tapis Magique project explores the relationship between auditory and physical interaction through an interactive knitted electronic textile interface. The researchers aim to tease the idea of music or an immersive sonic environment that is driven in real-time by movements from dance and choreography and allow dancers to have their own agency over producing and controlling the music.&nbsp;<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjMyNzU1Nzg3NDA4LVRhcGlzTWFnaXF1ZTEgY29weSAyLkpQRyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 766px;" class="fr-fic fr-dib">Credit Images: Irmandy Wicaksono/MIT Media LabThe project is motivated by traditional textile's extreme craftsmanship and artistry. Irmandy took some design inspiration from the cultural textiles of Indonesia, such as Javanese and Balinese Batik and Ikat. In these textiles, unique designs and patterns carry specific meanings and wishes. Complementing their traditional dance and music, they unitingly and harmoniously amplify a sense of community, identity, and expression. He hopes that by bringing functionality and interactivity to modern textiles, they will become even more appreciated, treasured, and personal and enhance our interaction with the environments and the digital world. Tapis Magique demonstrates the interplay between art and technology, highlighting the deep emotional link between contemporary textiles, dance, and music through the physical-digital connection.&nbsp;As textiles are highly soft, deformable, and palpable materials with a broad spectrum of textures, they are a great candidate for physical interfaces. Irmandy previously knitted a piano-patterned, multimodal musical cloth (<a href="https://www.digitaltrends.com/features/mit-knitted-keyboard/" target="_blank" rel="noopener noreferrer"></a><a href="https://www.digitaltrends.com/features/mit-knitted-keyboard/" rel="noopener noreferrer" target="_blank">KnittedKeyboard II</a>) that simultaneously responds to touch, pressure, stretch, and proximity. This 5-octave soft interface allows intimate and organic finger-fabric interaction. He also collaborated with a composer and keyboardist to demonstrate the multi-dimensionality of this e-textile instrument. With Tapis Magique, he is scaling the knitted e-textile technology and expanding its applications, incorporating footwork and body gestures.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjMyNzU2MzcyNTM0LVNjcmVlbiBTaG90IDIwMjEtMDktMjcgYXQgMTEuMjMuMTIgQU0ucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 766px;" class="fr-fic fr-dib">Knitting is an established textile manufacturing technique that has been pervasive in the garment and technical fabrics industry. &nbsp;In comparison to weaving, knitting has several advantages, including the ability to create intricate patterns and structures. Digital knitting machines now enable users to personalize and rapidly develop their textile design through a specialized visual programming environment and various functional and common yarns. It employs an array of needles or hooks that goes up and down to catch the yarns based on an instruction file. Each yarn is fed to the machine from a cone, passing through a tensioning mechanism towards a yarn carrier. These yarn carriers move sideways as the needles grab the yarn to form new loops. With advances in electronic materials and digital fabrication technologies, we can tune textile physical and at the resolution of a fiber, a loop structure, or a particle coating. These textiles can be fully customized from the micro to macro-scale and computationally designed and fabricated to form a seamless, heterogeneous, and multi-functional skin. This additive manufacturing process of machine-knitting enables the team to engineer patterns, colors, texture, thickness, elasticity, breathability, conductivity in discrete loops through fiber structures or material choices with as little waste as possible.&nbsp;<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjQ1ODE2NDYwNzM1LTE2NDU4MTY0NjA3MzQucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" id="isPasted" class="fr-fic fr-dii"> Tapis Magique is fabricated by knitting electrically-conducting yarns with other synthetic yarns, such as polyester, mink, thermoplastic, and luminous yarns, and fusing its multi-layer structures through thermoforming. The&nbsp;tapis&nbsp;design is composed of multi-layer knitted textiles. The top and bottom layers are orthogonal conductive line matrices knitted within a single operation using multi-material twisted yarns. The middle layer is a knitted piezoresistive textile, a pressure-sensitive layer that interfaces with the conductive matrices to create a sensing grid. The knitted piezoresistive textile is coated with conductive polymer called polypyrrole (PPy). &nbsp;Since it is piezoresistive, the resistance of this fabric sensor changes in correlation to the applied force. Like how a force-sensing resistor (FSR) works, a higher pressure compresses the conducting molecules coated into the fabric. These molecules then form a network, allowing more current to flow and reducing the resistance around the contact area.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjMyNzU2NDU1MDcwLVRhcGlzTWFnaXF1ZTUgY29weS5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 766px;" class="fr-fic fr-dib">In Tapis Magique, the researchers carefully consider the textile design from the yarn choices, textures, mechanical properties, to the aesthetics. The dense geometrical patterns of the stars scattered around the brushstroke details in the&nbsp;tapis&nbsp;represent 1800 pressure-sensing pixels and are inspired by the galactic space. Parametric design transformed these patterns into a 3-D spatial illusion to illustrate the multi-dimensionality of the sensor data. &nbsp;The furry textures from the synthetic mink yarns provide a soft tactility for physical feedback and give the tapis an intimate and comforting feel. The thermoplastic fibers were then steamed to melt the multi-layer knitted textiles into one rigid surface, giving it structural reinforcements. In addition, the outer-facing textile glows in the dark from the luminous yarns, bringing out the starry effects for night performance modes.&nbsp;The knitted conductive lines are connected to system hardware consisting of multiplexers, shift-registers, operational amplifiers, and a microcontroller that sequentially reads each pressure sensing pixel and sends it to a computer. These 60x30 pixels correspond to the pressure profile of the feet. They collectively generate continuous 3-D spatiotemporal sensor data correlated to the body posture, movements, and footwork. This data is then mapped into Musical Instrument Digital Interface (MIDI) streams to trigger and control discrete notes, continuous effects, and immersive soundscapes through science-inspired musical tools. MIDI is an industry-standard protocol that connects digital musical instruments, computers, tablets, and smartphones together and is used worldwide to create, produce, and perform music.<iframe src="https://player.vimeo.com/video/603497012" frameborder="0" allowfullscreen="" class="fr-draggable" style="width: 766px; height: 436px;" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true"></iframe> The team then designed several musical patches or pieces to invoke various emotions to inspire conversations between the choreographer and the instrument. Behind the scene, runs a digital modular synthesizer made of several patches, each for a different type of performance. The incoming stream of MIDI data is first fed into quantizer modules that align the notes to major, minor, and pentatonic scales, as well as mystic chords. The sounds are then generated by a collection of subtractive, additive, and granular synthesizers and are composed of discrete, melodic sounds with effects and continuously evolving soundscapes. "Venus Sunrise," one of the performance pieces demonstrated by the team, as shown in the video, presents a metaphorical celestial sound of the universe as the dancer is twirling around the stars, traveling through space and time. The team is now exploring other musical patches with different genres and ambiances.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjMyNzU2NzA2OTIyLVRhcGlzTWFnaXF1ZTggY29weSAzLkpQRyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 753px;" class="fr-fic fr-dib">Real-time audio system connected to Tapis Magique<hr> Tapis Magique&nbsp;provides a canvas for dancers and sound artists to program, compose, perform, and even collaborate with their own choreomusical pieces. It could also create an auditory-gestural synesthetic experience that invites and encourages the audiences to move on the carpet, expressing themselves through dance and evokes the bi-directional, intimate relationship between two complex art forms of dance and music.&nbsp;Irmandy Wicaksono, an MIT PhD student from the Responsive Environments Group, MIT Media Lab led the project and was involved in the design, fabrication, and development of Tapis Magique with the advice of MIT Professor of Media Arts and Sciences Joe Paradiso. He collaborated with MIT PhD student and sound artist Don Derek Haddad and dancer Loni Landon to demonstrate this interactive e-textile carpet and produce several musical and performance pieces.&nbsp;<h2 dir="ltr" id="isPasted">About the University Technology Exposure Program 2022</h2>Wevolver, in partnership with <a href="https://mouser.com/" rel="nofollow" target="_blank">Mouser Electronics</a> and&nbsp;<a href="https://www.ansys.com/academic" rel="noopener noreferrer" target="_blank">Ansys</a>,&nbsp;is excited to announce the launch of the University Technology Exposure Program 2022. The program aims to recognize and reward innovation from engineering students and researchers across the globe. Learn more about the program <a href="http://www.wevolver.com/student-program" target="_blank">here</a>.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjQ1ODE2NTA2MjM0LWV5SmlkV05yWlhRaU9pSjNaWFp2YkhabGNpMXdjbTlxWldOMExXbHRZV2RsY3lJc0ltdGxlU0k2SW1aeWIyRnNZUzh4TmpRMU5UVXhNalEyTVRJNExVSnliM1ZuYUhRZ2RHOGdlVzkxSUdKNUlDZ3hLUzVxY0djaUxDSmxaR2wwY3lJNmV5SnlaWE5wZW1VaU9uc2lkMmxrZEdnaU9qazFNQ3dpWm1sMElqb2lZMjkyWlhJaWZYMTkud2VicCIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 300px;" class="fr-fic fr-dib">

Dancer Loni Landon performing with Tapis Magique

Tapis Magique is a pressure-sensitive, knitted electronic textile carpet that generates 3D sensor data based on body gestures and drives an immersive sonic environment in real time. 


A choreomusical e-textile interactive carpet

For decades researchers have envisioned a world where digital user interfaces are seamlessly integrated with the physical environment, until the two are virtually indistinguishable from one another.&nbsp;This vision, though, is held up by a few boundaries. First, it&rsquo;s difficult to integrate sensors and display elements into our tangible world due to various design constraints. Second, most methods to do so are limited to smaller scales, bound by the size of the fabricating device.&nbsp;Recently, a group of researchers from MIT&rsquo;s Computer Science and Artificial Intelligence Laboratory (CSAIL) came up with SprayableTech, a system that lets users create room-sized interactive surfaces with sensors and displays. The system, which uses airbrushing of functional inks, enables various displays, like interactive sofas with embedded sensors to control your television, and sensors for adjusting lighting and temperature through your walls.<iframe src="https://www.youtube.com/embed/UXzyFbqGYOU?&wmode=opaque" frameborder="0" allowfullscreen="" class="fr-draggable" style="width: 789px; height: 444px;"></iframe>SprayableTech lets users channel their inner Picassos: After designing your interactive artwork in the 3D editor, it automatically generates stencils for airbrushing the layout onto a surface. Once they&rsquo;ve created the stencils from cardboard, a user can then add sensors to the desired surface, whether it&rsquo;s a sofa, a wall, or even a building, to control various appliances like your lamp or television. (An alternate option to stenciling is projecting them digitally.)&ldquo;Since SprayableTech is so flexible in its application, you can imagine using this type of system beyond walls and surfaces to power larger-scale entities like interactive smart cities and interactive architecture in public places,&rdquo; says Michael Wessely, postdoc in CSAIL and lead author on a new paper about SprayableTech. &ldquo;We view this as a tool that will allow humans to interact with and use their environment in newfound ways.&rdquo;The race for the smartest home has now been in the works for some time, with a large interest in sensor technology. It&rsquo;s a big advance from the enormous glass wall displays with quick-shifting images and screens we&rsquo;ve seen in countless dystopian films.&nbsp;The MIT researchers&rsquo; approach is focusing on scale, and creative expression. By using the airbrush technology, they&rsquo;re no longer limited to the size of the printer, the area of the screen-printing net, or the size of the hydrographic bath &mdash; and there&rsquo;s thousands of possible design options.&nbsp;Let&rsquo;s say a user wanted to design a tree symbol on their wall to control the ambient light in the room. To start the process, they would use a toolkit in a 3D editor to design their digital object, and customize for things like proximity sensors, touch buttons, sliders, and electroluminescent displays.&nbsp;Then, the toolkit would output the choice of stencils: fabricated stencils cut from cardboard, which are great for high-precision spraying on simple, flat, surfaces, or projected stencils, which are less precise, but better for doubly-curved surfaces.&nbsp;Designers can then spray on the functional ink, which is ink with electrically functional elements, using an airbrush. As a final step to get the system going, a microcontroller is attached that connects the interface to the board that runs the code for sensing and visual output.The team tested the system on a variety of items, including:<ul><li>a musical interface on a concrete pillar;</li><li>an interactive sofa that&rsquo;s connected to a television;</li><li>a wall display for controlling light; and</li><li>a street post with a touchable display that provides audible information on subway stations and local attractions.</li></ul>Since the stencils need to be created in advance via the digital editor, it reduces the opportunity for spontaneous exploration. Looking forward, the team wants to explore so-called &ldquo;modular&rdquo; stencils that create touch buttons of different sizes, as well as shape-changing stencils that adjust themselves based on a desired user interface shape.&nbsp;&ldquo;In the future, we aim to collaborate with graffiti artists and architects to explore the future potential for large-scale user interfaces in enabling the internet of things for smart cities and interactive homes,&rdquo; says Wessely.Wessely wrote the paper alongside MIT PhD student Ticha Sethapakdi, MIT undergraduate students Carlos Castillo and Jackson C. Snowden, MIT postdoc Isabel P.S. Qamar, MIT Professor Stefanie Mueller, University of Bristol PhD student Ollie Hanton, University of Bristol Professor Mike Fraser, and University of Bristol Associate Professor Anne Roudaut.&nbsp;

“Since SprayableTech is so flexible in its application, you can imagine using this type of system beyond walls and surfaces to power larger-scale entities like interactive smart cities and interactive architecture in public places,” says MIT postdoc Michael Wessely.  Photo: Jason Dorfman/MIT CSAIL

CSAIL's SprayableTech system lets users create large-scale interactive surfaces with sensors and displays using airbrushed inks.

Sprayable user interfaces

Flexible electronics isn&rsquo;t a new technology, but it has achieved a remarkable progress over the past years and has become increasingly important to many sectors such as consumer electronics, automotive, retail and healthcare. <a href="https://www.prnewswire.com/news-releases/idtechex-global-research-report-on-flexible-printed-and-organic-electronics-2019-2029-forecasts-players--opportunities-300799688.html" target="_blank">IDTechEx analysts forecast</a> that the total market for printed, flexible and organic electronics will grow from $31.7 billion in 2018 to $77.3 billion in 2029.&nbsp;Flexible electronics is a technology that allows you to build electronic circuits on flexible substrates thus making them bendable and stretchable. It enables new product paradigms that aren&rsquo;t possible with conventional semiconductors and glass substrates. Here we explore some of the attributes of flexible electronics that make this tech attractive to product designers and consumers alike.<h2>Flexible</h2>Transistors can be made from either inorganic or organic materials, or a mix of both. FlexEnable fabricates transistors using organic materials which replace the silicon and hard ceramic materials with soft, carbon-based materials. The organic thin-film transistors (OTFTs) we use are known as&nbsp;<a href="https://www.flexenable.com/services/otft-materials/" target="_blank" title="FlexiOM™">FlexiOM&trade;</a> - they are inherently flexible and have greater performance than amorphous silicon. These high-performance OTFTs can be processed at temperatures lower than 100&deg;C allowing for the use of&nbsp;lower cost thin film substrates thus enabling flexible devices.While flexible electronics have many applications, at FlexEnable we are primarily focused on flexible displays. Yet, our flexible OTFT platform can drive&nbsp;<a href="https://www.flexenable.com/technology/flexible-sensor-arrays/" target="_blank">flexible sensors</a> and other flexible devices. This platform has enabled the development of <a href="https://www.flexenable.com/technology/flexible-olcd/" target="_blank">flexible organic LCD</a>s&nbsp;(OLCDs) that can bend down to 10mm and be scaled to large areas making them suitable for a range of applications including automotive, consumer electronics, smart home appliances and digital signage.<h2>Light and thin</h2>Display thickness and weight are especially important features for applications that require large area displays such as automotive and digital signage. Using a flexible substrate (instead of glass) in combination with organic transistors helps make the whole stack very thin. For example at FlexEnable we use low-cost bio-based substrates such as TAC (tri acetyl cellulose) which are just a fraction of a tenth of a millimetre thick. As a result the entire OLCD is just 0.3mm thick (without the backlight). Moreover, the thinness and flexibility of&nbsp;<a href="https://www.flexenable.com/newsroom/breakthrough-in-glass-free-olcd-technology-enables-bezel-less-displays-for-notebooks/" target="_blank">OLCD enables bezel-less displays</a> through curved edges and folded borders. This brings huge value in applications like notebooks and tablets where borderless means bigger displays for the same sized device. <a href="https://www.flexenable.com/Blog/why-certain-plastic-substrates-are-an-ideal-alternative-to-glass-for-lcd/" target="_blank">The extreme thinness of TAC substrates also brings optical advantages to OLCD.</a><h2>Unbreakable</h2>One property of flexible electronics which deserves to be highlighted is their robustness. This makes a great difference for applications such as wearables, notebooks and other consumer electronics which traditionally feature glass-based displays or sensors. Incorporating an unbreakable, glass-free active matrix display could become a unique selling point for consumers.<h2>Cost advantage</h2>The processes and materials for manufacturing flexible electronics differ, but the aim is to make them lower cost than conventional electronics. <a href="https://www.flexenable.com/blog/enabling-flexible-electronics-from-the-roll/" target="_blank">Roll to roll printing</a> has been long considered the ultimate approach to the cost-effective manufacture of electronics over large and small areas. It will remove the waste of materials currently incurred in factories and will drive product costs down. However, there are a few steps to overcome before roll to roll printing becomes the norm.At FlexEnable we have developed a practical approach to the cost-effective manufacture of flexible electronics for flexible displays and sensors. Our processes are compatible with existing flat panel display lines meaning that all of the existing equipment can be reused. A maximum processing temperature below 100&deg;C allows for the use of&nbsp;lower cost flexible substrates (e.g. TAC) and minimises&nbsp;distortion (improves yield), whilst enabling a low cost, high yield method of handling flexible substrates.<h2>Innovation</h2>For brands and designers to keep innovating and developing next generation products, they need tools and components that will enable them to do this. Flexible electronics allow the development of flexible components such as flexible displays and sensors which remove form factor constraints and give designers creative freedom. A typical example is the automotive industry where designers are already thinking outside the box by reinventing the car interior with the help of flexible displays. French company Novares, for example, has demonstrated how flexible display technology can help improve design and safety by integrating conformable OLCDs supplied by FlexEnable&nbsp;into the interior of their demo car&nbsp;<a href="https://www.novaresteam.com/our-solutions/novacar-2-an-open-innovation-lab/" target="_blank">Nova Car 2</a>.

Flexible electronics isn’t a new technology, but it has achieved a remarkable progress over the past years and has become increasingly important to many sectors such as consumer electronics, automotive, retail and healthcare.

Five benefits of flexible electronics for displays and sensors

The rapid development of flexible and wearable electronics is giving rise to an exciting range of applications, from smart watches and flexible displays&mdash;such as smart phones, tablets, and TV&mdash;to smart fabrics, smart glass, transdermal patches, sensors, and more. With this rise, demand has increased for high-performance flexible batteries. Up to now, however, researchers have had difficulty obtaining both good flexibility and high energy density concurrently in lithium-ion batteries.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1578070497445-fig1a-1b-newsite.jpg">Schematic of the structure and the fabrication process of Yang&#39;s spine-like battery. (a) Schematic illustration of bio-inspired design, the vertebrae correspond to thick stacks of electrodes and soft marrow corresponds to unwound part that interconnects all the stacks. (b) The process to fabricate the spine-like battery, multilayers of electrodes were first cut into designed shape, then strips extending out were wound around the backbone to form spine-like structure.&nbsp;<style type="text/css"></style><style type="text/css"></style>Images And Video Courtesy: Yuan Yang/Columbia Engineering&nbsp;A team led by Yuan Yang, assistant professor of <a href="http://apam.columbia.edu/materials-science-and-engineering-0" target="_blank">materials science and engineering</a> in the <a href="http://apam.columbia.edu/" target="_blank">department of applied physics and mathematics</a> at <a href="http://www.engineering.columbia.edu/" target="_blank">Columbia Engineering</a>, has developed a prototype that addresses this challenge: a Li-ion battery shaped like the human spine that allows remarkable flexibility, high energy density, and stable voltage no matter how it is flexed or twisted. The <a href="http://onlinelibrary.wiley.com/doi/10.1002/adma.201704947/full" target="_blank">study</a> is published today in <a href="http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-4095" target="_blank">Advanced Materials</a>.&ldquo;The energy density of our prototype is one of the highest reported so far,&rdquo; says Yang. &ldquo;We&rsquo;ve developed a simple and scalable approach to fabricate a flexible spine-like lithium ion battery that has excellent electrochemical and mechanical properties. Our design is a very promising candidate as the first-generation, flexible, commercial lithium-ion battery. We are now optimizing the design and improving its performance.&rdquo;<iframe src="https://www.youtube.com/embed/JGpzSF0p1Xg?&wmode=opaque" frameborder="0" allowfullscreen="" class="fr-draggable" style="width: 1115px; height: 621px;"></iframe>Video demonstrating flexibility of Yang&#39;s lithium-ion battery powering a smart watch, in flat, flexed, and twisted configurations. <style type="text/css"></style><style type="text/css"></style>Images And Video Courtesy: Yuan Yang/Columbia Engineering&nbsp;Yang, whose <a href="http://blogs.cuit.columbia.edu/yanggroup/" target="_blank">group</a> explores the composition and structure of battery materials to realize high performance, was inspired by the suppleness of the spine while doing sit-ups in the gym. The human spine is highly flexible and distortable as well as mechanically robust, as it contains soft marrow components that interconnect hard vertebra parts. Yang used the spine model to design a battery with a similar structure. His prototype has a thick, rigid segment that stores energy by winding the electrodes (&ldquo;vertebrae&rdquo;) around a thin, flexible part (&ldquo;marrow&rdquo;) that connects the vertebra-like stacks of electrodes together. His design provides excellent flexibility for the whole battery.&ldquo;As the volume of the rigid electrode part is significantly larger than the flexible interconnection, the energy density of such a flexible battery can be greater than 85 percent of a battery in standard commercial packaging,&rdquo; Yang explains. &ldquo;Because of the high proportion of the active materials in the whole structure, our spine-like battery shows very high energy density&mdash;higher than any other reports we are aware of. The battery also successfully survived a harsh dynamic mechanical load test because of our rational bio-inspired design.&rdquo;<iframe src="https://www.youtube.com/embed/CDJpnqT_Y0c?&wmode=opaque" frameborder="0" allowfullscreen="" class="fr-draggable" style="width: 1115px; height: 630px;"></iframe>Video of the dynamic mechanical load test demonstrating flexibility of Yang&#39;s lithium-ion battery. <style type="text/css"></style><style type="text/css"></style>Images And Video Courtesy: Yuan Yang/Columbia Engineering&nbsp;Yang&rsquo;s team cut the conventional anode/separator/cathode/separator stacks into long strips with multiple &ldquo;branches&rdquo; extending out 90 degrees from the &ldquo;backbone.&rdquo; Then they wrapped each branch around the backbone to form thick stacks for storing energy, like vertebrae in a spine. With this integrated design, the battery&rsquo;s energy density is limited only by the longitudinal percentage of vertebra-like stacks compared to the whole length of the device, which can easily reach over 90 percent.The battery shows stable capacity upon cycling, as well as a stable voltage profile no matter how it is flexed or twisted. After cycling, the team disassembled the battery to examine the morphology change of electrode materials. They found that the positive electrode was intact with no obvious cracking or peeling from the aluminum foil, confirming the mechanical stability of their design. To further illustrate the flexibility of their design, the researchers continuously flexed or twisted the battery during discharge, finding that neither bending nor twisting interrupted the voltage curve. Even when the cell was continuously flexed and twisted during the whole discharge, the voltage profile remained. The battery in the flexed state was also cycled at higher current densities, and the capacity retention was quite high (84 percent at 3C, the charge in 1/3 of an hour). The battery also survived a continuous dynamic mechanical load test, rarely reported in earlier studies.&ldquo;Our spine-like design is much more mechanically robust than are conventional designs,&rdquo; Yang says. &ldquo;We anticipate that our bio-inspired, scalable method to fabricate flexible Li-ion batteries could greatly advance the commercialization of flexible devices.&rdquo;

Schematic of the structure and the fabrication process of Yang's spine-like battery. (a) Schematic illustration of bio-inspired design, the vertebrae correspond to thick stacks of electrodes and soft marrow corresponds to unwound part that interconnects all the stacks. (b) The process to fabricate the spine-like battery, multilayers of electrodes were first cut into designed shape, then strips extending out were wound around the backbone to form spine-like structure. Images And Video Courtesy: Yuan Yang/Columbia Engineering

Shaped like a spine, new design enables remarkable flexibility, high energy density, and stable voltage no matter how it is flexed or twisted

Engineers Develop Flexible Lithium Battery for Wearable Electronics

Researchers from Carnegie Mellon University&rsquo;s College of Engineering and the Institute of Systems and Robotics of the University of Coimbra, Portugal have developed a simple, efficient method to make robust, highly flexible, tattoo-like circuits for use in wearable computing. The low-cost process adds trace amounts of an electrically-conductive, liquid metal alloy to tattoo paper that adheres to human skin. These ultrathin tattoos can be applied easily with water, the same way one would apply a child&rsquo;s decorative tattoo with a damp sponge.Other tattoo-like electronics either require complex fabrication techniques inside a cleanroom or lack the material performance required for stretchable digital circuit functionality on skin.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1573729030390-1011-em-carmel-tattoo-1.png" style="width: 1114px;" class="fr-fic fr-dib">The tattoos can conform and adhere to highly curved 3D surfaces, like a model of the human brain.Carmel Majidi, an associate professor of mechanical engineering and the director of the&nbsp;<a href="http://sml.me.cmu.edu/" rel="noopener" target="_blank">Soft Machines Lab</a> at Carnegie Mellon, and Mahmoud Tavakoli, the director of the&nbsp;<a href="https://sites.google.com/site/fsrlabisr/" rel="noopener" target="_blank">Soft and Printed Microelectronics Laboratory</a> <a href="https://sites.google.com/site/fsrlabisr/" target="_blank"></a>at the University of Coimbra, teamed up to develop methods for direct printing of stretchable electronic circuits.Their collaboration succeeded.&nbsp;&ldquo;This is a breakthrough in the printed electronics area,&rdquo; said Tavakoli. &ldquo;We showed for the first time that inkjet-printed patterns of silver nano particles can be sintered at room temperature using the gallium indium alloy. Removing the need for high temperature sintering makes our technique compatible with thin-film and heat sensitive substrates.&rdquo;<blockquote>The technique is simple. The tattoos are ultrathin, very stretchable, and inexpensive to produce.</blockquote>In addition to low-cost processing, these tattoos provide other advantages. Because they have mechanical properties similar tolightweight fabrics, they remain functional under bending, folding, twisting, and strains above 30% (which is the typical stretchability of human skin). They can conform and adhere to highly curved 3D surfaces, like a model of a human brain or a lemon.Applications for ultrathin, compliant tattoos include epidermal biomonitoring, soft robotics, flexible displays, and 3D-transferable printed electronics.The findings were published in Advanced Materials&nbsp;in a paper titled &ldquo;<a href="https://doi.org/10.1002/adma.201801852" rel="noopener" target="_blank">EGaIn‐Assisted Room‐Temperature Sintering of Silver Nanoparticles for Stretchable, Inkjet‐Printed, Thin‐Film Electronics</a>.&rdquo; Carmel Majidi explains the technology behind the electronic tattoos:<iframe src="https://www.youtube.com/embed/OaITzyMptFQ?&wmode=opaque" frameborder="0" allowfullscreen="" class="fr-draggable" style="width: 1115px; height: 619px;"></iframe>Video credit: Institute of Systems and Robotics of the University of Coimbra, Portugal and College of Engineering, Carnegie Mellon University

The ultrathin tattoos can be applied and removed easily with water, similar to deorative, temporary tattoos.

flexible electronics

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