Following the breakthrough with their first sweating artificial skin two years ago, Danqing Liu&rsquo;s multidisciplinary team hasn&rsquo;t been sitting still. Their goal: an artificial skin that sweats as naturally as possible. They have succeeded in this, as can be read in their article in Angewandte Chemie. There, they explain how they managed to be the first team in the world to be able to accurately control where, when and how much an artificial skin sweats and also where the liquid collects.&nbsp;<h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1660531451306-csm_illustration+2_paper_a9f6306874.jpg" style="width: 766px;" class="fr-fic fr-dib">Schematic representation of the secretion of liquid by the artificial skin with different external stimuli. Photo: Danqing Liu.&nbsp;Sweating robots</h2>In the previous breakthrough by the team, it became apparent that an artificial skin that can sweat on command could have numerous practical applications. Back then, the artificial skin could secrete the fluid evenly and equally everywhere. An evenly sweating artificial skin can help cool the surface of robots. In social applications, it could help make the robot as human-like as possible, which includes sweating. Or consider special bandages that can deliver controlled drugs to human skin or to a wound surface such as a burn.These applications will only become more tangible as this new invention allows them to control where the artificial skin excretes fluid within a few micrometer. Not only that, but the researchers now control how much and for how long the fluid is released by the artificial skin, as well as where the fluid collects and when it is time to reabsorb it.The release of fluid is stimulated by UV light. By then applying voltage to the underlying electrical grid, the fluid collects in the desired places. Through clever design of the grid, this can be completely controlled and creates a very natural sweat pattern. Think about yourself: on a hot day, sweat also collects in specific places on your face. This artificial skin brings us a big step closer to imitating the natural behavior of the skin.<h2 id="isPasted">Multidisciplinary team</h2><a href="https://www.tue.nl/en/research/researchers/danqing-liu/" target="_blank">Danqing Liu</a>, assistant professor at the department of&nbsp;<a href="https://www.tue.nl/en/our-university/departments/chemical-engineering-and-chemistry/" target="_blank">Chemical Engineering &amp; Chemistry</a> and affiliated with the&nbsp;<a href="https://www.tue.nl/en/research/institutes/institute-for-complex-molecular-systems/" target="_blank">ICMS institute</a>, and het postdoc&nbsp;<a href="https://www.tue.nl/en/research/researchers/yuanyuan-zhan/" target="_blank">YuanYuan Zhan</a>&rsquo;s drive and enthusiasm are infectious to anyone who speaks to her. In Liu&rsquo;s&nbsp;<a href="https://assets.tue.nl/fileadmin/icms/Highlights%20magazine/TUE_ECHT%204391_ICMS%20magazine_juni_2022_LR.pdf#page=10" target="_blank">special lab</a>, she has gathered a unique multidisciplinary team around her. The lab also has the equipment to do electrotechnical, chemical and physical research in conjunction with industrial design, which is fairly exceptional within the university. Together, they are doing research on several promising materials based on liquid crystals, better known for LCD screens.&ldquo;It&rsquo;s so cool to see what our team can accomplish with these materials based on outside stimuli!&rdquo; Liu enthusiastically explains. &ldquo;I have a very broad technical background, so I can brainstorm with each team member. Still, everybody&rsquo;s specialisms were essential to achieving the results that we are now demonstrating.&rdquo;<iframe src="https://www.youtube.com/embed/yixbRf5RRDY?&wmode=opaque&rel=0&enablejsapi=1&origin=https://www.wevolver.com" frameborder="0" allowfullscreen="" class="fr-draggable" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" style="width: 767px; height: 404px;"></iframe>SWEATING ARTIFICIAL SKIN.&nbsp;In the video presented here, the different phases of liquid secretion are visualized for clarification. The first secretion of the chosen liquid is stimulated with UV-light. Next, the liquid collects where the electrical grid dictates. Finally the liquid is reabsorbed through the pores in the skin, when the electricity and UV-light are switched off.<h2 id="isPasted">Unique combination of properties</h2>What makes this new iteration of artificial skin by Liu&rsquo;s team so unique is the far-reaching control that they have over the skin&rsquo;s behavior: secreting, dispersing or collecting and reabsorbing the liquid, a process which they control via free UV light and electricity. Unsurprisingly, their work is generating excitement in materials science.&ldquo;My motivation is to develop useful materials. I therefore like to start a project with a clear goal in mind. In this case, we&rsquo;re looking for a new material for a useful medical application,&rdquo; says Liu. &ldquo;And that takes time. It may seem like it&rsquo;s now going quickly, but from the first inspired idea to where we are now with this breakthrough has taken us over ten years. And we&rsquo;re not done yet.&ldquo;We started with the idea of seeing what we could do with liquid crystals in soft robotics in 3D. The focus then shifted to a 2D robot skin. We were keen to complement traditional robotics rather than compete with it. With the skin, we found that we could control the topology (mountains and valleys at the micrometer scale).&ldquo;We could use that as a coating to shake sand off of the Mars Rover&rsquo;s solar panels, for instance. Another application we&rsquo;ve worked out is alternating between sticky and non-sticky sections of the coating. By choosing which material is on the tops of the mountains and which is in the valleys, we could ensure that something is sticky or not. This could be a better method than a vacuum cup, especially for fragile or delicate parts like thin glass.&rdquo;And this brings us to Liu&rsquo;s team&#39;s current research. Together, they are working on that one dream: not simply imitating nature but helping it to evolve by adding to what is already possible. And it seems fair to conclude that they are succeeding in doing so with their unique liquid crystal materials.Yuanyuan Zhan and Danqing Liu&rsquo;s article &ldquo;<a href="https://onlinelibrary.wiley.com/doi/10.1002/anie.202207468" target="_blank">Light- and Field-Controlled Diffusion, Ejection, Flow and Collection of Liquid at a Nanoporous Liquid Crystal Membrane</a>&rdquo; appeared as a top 5%early access online article in Angewandte Chemie on July 5th,2022.<hr>This article was first published here:&nbsp;<a href="https://www.tue.nl/en/news-and-events/news-overview/27-07-2022-artificial-skin-sweats-on-command/" id="isPasted" rel="noopener noreferrer" target="_blank">https://www.tue.nl/en/news-and-events/news-overview/27-07-2022-artificial-skin-sweats-on-command/</a>

Yuanyuan Zhan with experimental results. Photo: Yuanyuan Zhan

The sophisticated artificial skin sweats where and how much the researchers want it to. This was reported in an Angewandte Chemie article by Danqing Liu and first author Yuanyuan Zhan.

Artificial skin sweats on command

The skin of cephalopods, such as octopuses, squids and cuttlefish, is stretchy and smart, contributing to these creatures&rsquo; ability to sense and respond to their surroundings. A Penn State-led collaboration has harnessed these properties to create an artificial skin that mimics both the elasticity and the neurologic functions of cephalopod skin, with potential applications for neurorobotics, skin prosthetics, artificial organs and more.  &nbsp;Led by&nbsp;<a href="https://www.bme.psu.edu/department/directory-detail-g.aspx?q=cmy5358" target="_blank">Cunjiang Yu</a>, Dorothy Quiggle Career Development Associate Professor of Engineering Science and Mechanics and Biomedical Engineering, the team published its findings on June 1 in the&nbsp;<a href="https://www.pnas.org/doi/abs/10.1073/pnas.2204852119" target="_blank">Proceedings of the National Academy of Sciences</a>. &nbsp;Cephalopod skin is a soft organ that can endure complex deformations, such as expanding, contracting, bending and twisting. It also possesses cognitive sense-and-respond functions that enable the skin to sense light, react and camouflage its wearer. While artificial skins with either these physical or these cognitive capabilities have existed previously, according to Yu, until now none has simultaneously exhibited both qualities &mdash; the combination needed for advanced, artificially intelligent bioelectronic skin devices.  &nbsp;&ldquo;Although several artificial camouflage skin devices have been recently developed, they lack critical noncentralized neuromorphic processing and cognition capabilities, and materials with such capabilities lack robust mechanical properties,&rdquo; Yu said. &ldquo;Our recently developed soft synaptic devices have achieved brain-inspired computing and artificial nervous systems that are sensitive to touch and light that retain these neuromorphic functions when biaxially stretched.&rdquo;  &nbsp;To simultaneously achieve both smartness and stretchability, the researchers constructed synaptic transistors entirely from elastomeric materials. These rubbery semiconductors operate in a similar fashion to neural connections, exchanging critical messages for system-wide needs, impervious to physical changes in the system&rsquo;s structure. The key to creating a soft skin device with both cognitive and stretching capabilities, according to Yu, was using elastomeric rubbery materials for every component. This approach resulted in a device that can successfully exhibit and maintain neurological synaptic behaviors, such as image sensing and memorization, even when stretched, twisted and poked 30% beyond a natural resting state.  &nbsp;&ldquo;With the recent surge of smart skin devices, implementing neuromorphic functions into these devices opens the door for a future direction toward more powerful biomimetics,&rdquo; Yu said. &ldquo;This methodology for implementing cognitive functions into smart skin devices could be extrapolated into many other areas, including neuromorphic computing wearables, artificial organs, soft neurorobotics and skin prosthetics for next-generation intelligent systems.&rdquo; &nbsp;The Office of Naval Research Young Investigator Program and the National Science Foundation supported this work.&nbsp;Yu is also affiliated with the Material Research Institute and the Department of Materials Science and Engineering in the College of Earth and Mineral Sciences. &nbsp;Co-authors include Hyunseok Shim, Seonmin Jang and Shubham Patel, Penn State Department of Engineering Science and Mechanics; Anish Thukral and Bin Kan, University of Houston Department of Mechanical Engineering; Seongsik Jeong, Hyeson Jo and Hai-Jin Kim, Gyeongsang National University School of Mechanical and Aerospace Engineering; Guodan Wei, Tsinghua-Berkeley Shenzhen Institute; and Wei Lan, Lanzhou University School of Physical Science and Technology. &nbsp;

A Penn State-led collaboration developed an artificial skin made completely of rubber that mimics both the elasticity and cognitive characteristics found in octopuses and other cephalopods.    Credit: Volodymyr Ivanenko/iStock. All Rights Reserved.

Penn State-led researchers develop first artificial skin to maintain cognitive characteristics when deformed.

Rubbery camouflage skin exhibits smart and stretchy behaviors

<section id="isPasted">In industry, people work with robots. While this can accelerate productivity, it does come with health and safety risks. As a result, some robots must be kept separate from human workers. This comes at a heavy financial cost and negatively affects human-robot interactions. If there were sensors on robots to detect a person, then these issues could be solved, but current sensors rely on impractical, rigid, and thick electronics. TU/e researchers have designed a way to make flexible, thin, and accurate sensor electronics that outperform many current sensors. The new breakthrough is published in the Nature Electronics.</section><section tabindex="-1">Our world is filled with robots. From robot vacuum cleaners to robot dog walkers, we have incorporated robots in many aspects of daily life. In industry, robots have helped to automate many tasks, and in the process, they provide both an accuracy and speed that are beyond human capabilities.However, that doesn&rsquo;t mean that humans and robots do not work closely together in industry. &ldquo;Many industrial operations require close human-robot interactions&rdquo;, says researcher Marco Fattori from the department of Electrical Engineering and the TU/e startup MicroAlign. &ldquo;This means that the robots need accurate proximity sensors to check if someone gets too close to the robot. Once someone is detected, the robot shuts down to prevent any injuries to the person.&rdquo;Many of the current sensors are based on silicon components, but these are rigid and thick, which makes it difficult and costly to place them on the surface of the robot.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1654095377288-csm_Fattori+Flexible+electronics_29eb6db461.jpg" style="width: 766px;" class="fr-fic fr-dib">Source: Marco Fattori.&nbsp;<h2 id="isPasted">New flexible printed electronics</h2>&ldquo;The alternative is flexible printed electronics, but this kind of electronics has lower capabilities compared to silicon chips,&rdquo; notes Eugenio Cantatore from the department of Electrical Engineering. &ldquo;Flexible electronics are slow and noisy, which negatively affects its accuracy. But unlike silicon sensors, the flexible ones can be placed over large surface areas, are cheap to make, and can be produced in large quantities.&rdquo;So, to solve the issue of making accurate flexible electronics, Fattori and Cantatore, in collaboration with researchers based in France, Austria, and the UK developed new flexible electronics made by printing organic materials based on polymers. The printing approach allows for the placement of front-end electronics (the first electronics layer after the sensor) in each pixel of the device.&ldquo;In effect, we printed electronics on a plastic or foil sheet, then we placed the sensors on another foil. After that we laminated the two foils together, leading to an ultra-flexible and thin sensor,&rdquo; says Fattori. &ldquo;This combination enhances signal quality in comparison to previous sensors.&rdquo;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1654095428535-csm_Fattori+Main+text+Robot+in+action+CROPPED_dda1c5c3cf.jpg" style="width: 766px;" class="fr-fic fr-dib">Source: Marco Fattori.&nbsp;<h2 id="isPasted">The robot arm</h2>For this study, the researchers placed long-wavelength infrared organic pyroelectric sensors (heat sensors) in the flexible foil. &ldquo;We created a large flexible sheet filled with heat sensors that can be used to cover a structure, such as a robotic arm for example,&rdquo; says Cantatare.And that&rsquo;s exactly what the researchers did. They wrapped a flexible sheet of heat sensors around a robotic arm to simulate an industrial work environment where a human works close to a robot.&ldquo;The flexible sensor acts like a sort of &lsquo;artificial skin&rsquo; for the robot. The heat sensors allow the robot to detect the presence of a moveable heat source, such as a person, from a distance of up to 0.4 meters away,&rdquo; notes Fattori. &ldquo;What&rsquo;s more, the sensors can also detect a human hand approaching from different directions and not just from directly in front of it.&rdquo; &nbsp;<h2>Great promise</h2>Besides applications in industry with robots, the researchers note that the ability to produce affordable flexible sensors could be useful in numerous other fields, such as healthcare.For example, they could be used to map pressure distributions on a mattress, and thus help patients avoid bedsores. In addition, they could be used to check if elderly people experience falls in their home or in care homes by embedding sensors in the floors. These kind of sensors could even be adapted to monitor the integrity of airplane wings.This research is part of a complex European collaborative project called ATLASS. &ldquo;After years of work, we have demonstrated for the first time with a practical, useful example, the great promise of low-cost printed sensing surfaces that include electronics,&rdquo; says Cantatore. &ldquo;We are excited to use these results to initiate new research endeavors at TU/e.&rdquo;<hr><h3>Paper information</h3><a href="https://www.nature.com/articles/s41928-022-00762-6" target="_blank">A printed proximity-sensing surface based on organic pyroelectric sensors and organic thin-film transistor electronics</a>, Fattori et al, Nature Electronics (2022).<style type="text/css" id="isPasted"></style><style type="text/css"></style>This article was first published here:&nbsp;<a href="https://www.tue.nl/en/news-and-events/news-overview/30-05-2022-new-printing-method-for-artificial-skin-containing-heat-sensors/" id="isPasted" rel="noopener noreferrer" target="_blank">https://www.tue.nl/en/news-and-events/news-overview/30-05-2022-new-printing-method-for-artificial-skin-containing-heat-sensors/</a></section>

Robot arms could become safer in industrial settings by applying an artificial skin containing proximity heat sensors to detect humans in all directions.

New printing method for artificial "skin" containing heat sensors

In this episode, we talk about how a group of University of Michigan researchers were inspired by the adaptive immune system found in humans to fortify vulnerable neural networks and a joint effort between Pohang University of Science and Technology and Ulsan National Institute of Science and Technology to create electric skin with unmatched performance. As always, you can find these and other interesting &amp; impactful engineering articles on Wevolver.com.&nbsp;<iframe height="200px" width="100%" frameborder="no" scrolling="no" seamless="" src="https://player.simplecast.com/43d45afd-8dcf-45ad-abb4-02c30cff4eb6?dark=false" class="fr-draggable" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true"></iframe> <hr>This podcast is sponsored by <a href="https://www2.mouser.com/" id="isPasted" rel="nofollow" target="_blank">Mouser Electronics</a>. &nbsp; &nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1648558505214-Mouser-sponsor-1-a.jpg" style="width: 766px;" class="fr-fic fr-dib"><hr><h3 id="isPasted">EPISODE NOTES</h3>(2:08) -&nbsp;<a href="https://www.wevolver.com/article/immune-to-hacks-inoculating-deep-neural-networks-to-thwart-attacks" target="_blank">Immune To Hacks</a>(12:50) - <a href="https://www.wevolver.com/article/a-spectrum-of-spikes-allows-this-novel-electronic-skin-to-sense-touch-like-we-do" target="_blank">Electronics Sense Touch</a><hr id="isPasted">About the podcast:Every day, some of the most innovative universities, companies, and individual technology developers share their knowledge on Wevolver. To ensure we can also provide this knowledge for the growing group of podcast listeners, we started a collaboration with two young engineers, Daniel Scott Mitchell &amp; Farbod Moghaddam who discuss the most interesting content in this podcast series.&nbsp;To learn more about this show, please visit the&nbsp;<a href="https://www.wevolver.com/profile/the.next.byte" target="_blank">shows page</a>. By following the page, you will get automatic updates by email when a new show is published.Be sure to give us a follow and review on&nbsp;<a href="https://podcasts.apple.com/nl/podcast/the-next-byte/id1548255861?l=en" rel="nofollow" target="_blank">Apple</a> podcasts,&nbsp;<a href="https://open.spotify.com/show/6lPPsRtegnivsRUEsQ09R7?si=IPMiah7xT_apJtPjqvXMlA" rel="nofollow" target="_blank">Spotify</a>, and most of your favorite podcast platforms!

Two prototype position-encoded spike spectrum (PESS) sensors, one showing its ability to flex and confirm to non-linear surfaces, have been proven experimentally.

In this episode, we talk about how a group of researchers were inspired by the adaptive immune system found in humans to fortify vulnerable neural networks and a joint effort between universities to create electric skin with unmatched performance.

Podcast: Immune System Inspired AI & Electric Skin

This article was discussed in our <a data-saferedirecturl="https://www.google.com/url?q=https://www.wevolver.com/profile/the.next.byte&source=gmail&ust=1648450959370000&usg=AOvVaw3quhsJUxQ1lZ0LmFmeQflQ" href="https://www.wevolver.com/profile/the.next.byte" id="isPasted" rel="noopener noreferrer" target="_blank">Next Byte podcast</a>.&nbsp;<iframe height="200px" width="100%" frameborder="no" scrolling="no" seamless="" src="https://player.simplecast.com/43d45afd-8dcf-45ad-abb4-02c30cff4eb6?dark=false" class="fr-draggable" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true"></iframe>The full article will continue below.<hr>Electronic skin, which weaves technology into a flexible and stretchable substrate designed to mimic human skin, offers potential for everything from highly-dexterous robotics to sensory-feedback prosthetics, health monitoring, medical implants, haptics, and more. Current implementations, however, often suffer from high power draw and slow response times.A new approach, based on what a team of researchers at the Pohang University of Science and Technology (POSTECH) and the Ulsan National Institute of Science and Technology (UNIST) has termed position-encoded spike spectrum (PESS), could change that &mdash; offering a high-resolution, high-sensitivity artificial tactile system which manages to also be easy to manufacture at scale.<h1>Spiking sensors</h1>The concept is borrowed from biology: The human somatosensory system offers event-driven spike generation, with parallel processing allowing sensations to be felt without delay. While rival approaches aimed at mimicking the same process electronically exist, they center around analog-to-digital converters (ADCs) which limit their resolution and add bulk.What first author Taeyeong Kim and colleagues have developed, by contrast, is a sensory system offering much the same capabilities as the human sense of touch. A mixed ion-electron conductor (MIEC) hosts artificial receptors designed with varying ion relaxation times &mdash; turning touch into a spectrum of spike signals, rather than a single reading.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjQ4MjMzMzc1MjUxLWVza2luMi5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 300px;" class="fr-fic fr-dib" alt="A diagram showing a position-encoded spike spectrum (PESS) electronic skin sensor, attached to the surface of a human thumb. As the thumb grasps a pencil, a spike spectrum is created - split into characteristic spikes, which offer position information, and auxiliary spikes, which capture pressure.">The PESS sensor system captures both position and pressure by encoding information into a spectrum of spikes which are rapidly decoded and identified.This spike spectrum is key to the responsiveness of the system itself: The relaxation time of each spike can be decoded in real time, its creators claim, to identify exactly where and how the skin is being touched. The overall delay was measured at of 2ms for the auxiliary spikes, which carry pressure information, and 10ms for the characteristic spikes, which offer position.At the same time, the sensor system is surprisingly simple. The prototype was produced using a combination of the MIEC film and PEDOT:PSS as a conducting polymer, applied via spray coating through a patterned stencil mask &mdash; each hole in the mask corresponding to an individual receptor. Layers of silver and gold act as electrodes in the system.<h1>Touchable proof</h1>To prove the concept, the team created a compact prototype measuring 2&times;2cm (around 0.8&times;0.8&quot;) and featuring an impressive 529 individual receptors. Despite this, it required only two signal addressing lines &mdash; a major advantage, its creators claim, over alternatives which rely on time-division multiple access (TMDA) addressing, and a closer analog to the highly-parallel human somatosensory system.As the prototype was touched, the resulting spikes were analyzed by a decoding algorithm in just 2ms. The algorithm, in turn, offers inferred tactile information based on analysis of the characteristic and auxiliary spikes: Position, size, rough shape, and even pressure down to 1.5kPa, all reported with high accuracy.<iframe src="https://www.youtube.com/embed/gq0xN2U1HDY?&wmode=opaque&rel=0&enablejsapi=1&origin=https://www.wevolver.com" allowfullscreen="" class="fr-draggable" width="640" height="360" frameborder="0" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true"></iframe> In further testing, the team showcased the skin&rsquo;s ability to detect two-dimensional movement, in the form of sensing letters drawn on its surface, and of providing real-time feedback when applied to a robot arm. In these tests, the robot arm was given the task of grasping a metal sphere, rotating, allowing the ball to fall to the bottom of the grip, then shaking it repeatedly &mdash; detecting slippage through the PESS system and tightening its grip instantly in order to prevent the ball from being dropped.<h1>Further work</h1>There&rsquo;s the potential for improvement, too. The team suggests that the application of &ldquo;machine learning-based decoding&rdquo; could allow the PESS system to determine more complicated shapes than is possible using the existing algorithm, while experimental results suggest the possibility of extending the system to omni-directional tactile perception.&ldquo;Converting the external stimuli into spike signals and processing them is a groundbreaking idea that mimics how the human nervous system processes information,&rdquo; says Sung-Phil Kim, UNIST professor and co-corresponding author of the paper detailing the breakthrough.&ldquo;If a new AI model is developed using this spike information encoding method, robot tactile intelligence can be further developed and effectively applied to next-generation semiconductor technologies such as neuromorphic chips.&rdquo;<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjQ4MjMzMzkxODYyLWVza2luMy5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 300px;" class="fr-fic fr-dib" alt="A diagram showing the prototype sensor, and the layers from which it is manufactured. From top to bottom: PET, Au, artificial receptors, PET separator, adhesive, Au, Ag/SBS, and silicone elastomer.">The PESS sensors are relatively simple to produce, though work still needs to be done on reliably controlling the thickness of the PEDOT:PSS layer.A sensor variant which integrates four separate sensing systems into a single device, meanwhile, boosts the stationary spatial resolution to 80 receptors per square centimeter (80/cm2) and for dynamic sensing to 132/cm2 &mdash; a figure which the team suggests could be increased still further with improvements to measurement equipment and the sensor&rsquo;s stencil layer.One issue standing in the way of production use, however, is in creating a PEDOT:PSS layer of reliable and repeatable thickness. &ldquo;Unfortunately,&rdquo; the team admits, &ldquo;delicate thickness control of the PEDOT:PSS coating on the target positions for the characteristic receptors was not achieved yet in this study.&rdquo;The team&rsquo;s work has been published in the journal <cite><a href="https://www.science.org/doi/10.1126/scirobotics.abl5761" target="_blank">Science Robotics</a></cite> under closed-access terms.<h1>Reference</h1>Taeyeong Kim, Jaehun Kim, Insang You, Joosung Oh, Sung-Phil Kim, and Unyong Jeong: <cite>Dynamic tactility by position-encoded spike spectrum, Science Robotics Vol. 7 Iss. 63</cite>. DOI <a href="https://doi.org/10.1126/scirobotics.abl5761" target="_blank">10.1126/scirobotics.abl5761</a>.

Using a highly-scalable approach to creating dense sensor networks, yet requiring only a pair of address lines, these researchers have taken inspiration from the human somatosensory system for a rapid-response sensitive sense of electronic touch.

A spectrum of spikes allows this novel electronic skin to sense touch like we do

Of the many ways that humans make sense of our world&mdash;with our eyes, ears, nose and mouth&mdash;none is perhaps less appreciated than our tactile and versatile hands.Thanks to our sensitive fingertips, we can feel the heat before we touch the flame, or sense the softness of a newborn&rsquo;s cheek.But people with prosthetic limbs live in a world without touch. Restoring some semblance of this sensation has been a driving force behind Stanford chemical engineer and K.K.Lee professor in the school of engineering <a href="https://mandrillapp.com/track/click/30855492/profiles.stanford.edu?p=eyJzIjoiWTVNaFpWY2NQcm5kTE1FYWF6a1BnNHFIbWMwIiwidiI6MSwicCI6IntcInVcIjozMDg1NTQ5MixcInZcIjoxLFwidXJsXCI6XCJodHRwczpcXFwvXFxcL3Byb2ZpbGVzLnN0YW5mb3JkLmVkdVxcXC96aGVuYW4tYmFvXCIsXCJpZFwiOlwiYjVkZGU4ZGU0YzEyNDlmMzg0MWYyNDMyN2FmMmQzMzdcIixcInVybF9pZHNcIjpbXCJkMGY0ZGMxYjBmMDE3OTkzNjhmOGE4NzJlMmViNzQ3ZTFjZmNmMjBkXCJdfSJ9" target="_blank">Zhenan Bao</a>&rsquo;s <a href="https://mandrillapp.com/track/click/30855492/engineering.stanford.edu?p=eyJzIjoiV0hLZGhnRnRPU0JiNHdzeVNOcmFkcDhyR0hFIiwidiI6MSwicCI6IntcInVcIjozMDg1NTQ5MixcInZcIjoxLFwidXJsXCI6XCJodHRwczpcXFwvXFxcL2VuZ2luZWVyaW5nLnN0YW5mb3JkLmVkdVxcXC9tYWdhemluZVxcXC9hcnRpY2xlXFxcL3poZW5hbi1iYW8tcXVlc3QtZGV2ZWxvcC1hcnRpZmljaWFsLXNraW5cIixcImlkXCI6XCJiNWRkZThkZTRjMTI0OWYzODQxZjI0MzI3YWYyZDMzN1wiLFwidXJsX2lkc1wiOltcIjNiMTBjYzkwMzliNDc3ODRhNDcyZjMyM2M3OWFjYjg5YjllN2EzMDJcIl19In0" target="_blank">decades-long quest</a> to create stretchable, electronically-sensitive synthetic materials. Such a breakthrough could one day serve as skin-like coverings for prosthetics. But in the near term, this same technology could become the foundation for the evolution of new genre of flexible electronics that are in stark contrast with rigid smartphones that many of us carry, gingerly, in our back pockets.Now, in a Feb. 19&nbsp;Nature&nbsp;paper, Bao and her team describe two technical firsts that could bring this 20-year goal to fruition: the creation of a stretchable, polymer circuitry with integrated touch-sensors to detect the delicate footprint of an artificial ladybug. And while this technical achievement is a milestone, the second, and more practical, advance is a method to mass produce this new class of flexible, stretchable electronics&mdash;a critical step on the path to commercialization, Bao said.&ldquo;Research into synthetic skin and flexible electronics has come a long way, but until now no one had demonstrated a process to reliably manufacture stretchable circuits,&rdquo; Bao said.Bao&rsquo;s hope is that manufacturers might one day be able to make sheets of polymer-based electronics embedded with a broad variety of sensors, and eventually connect these flexible, multipurpose circuits with a person&rsquo;s nervous system. Such a product would be analogous to the vastly more complex biochemical sensory network and surface protection &ldquo;material&rdquo; that we call human skin, which can not only sense touch, but temperature and other phenomena, as well. But long before artificial skin becomes possible, the processes reported in this Nature paper will enable the creation of foldable, stretchable touchscreens, electronic clothing or skin-like patches for medical applications.<h2>Layer by layer</h2>Bao said their production process involves several layers of new-age polymers, some that provide the material&rsquo;s elasticity and others with intricately patterned electronic meshes. Still, others serve as insulators to isolate the electronically sensitive material. One step in the production process involves the use of an inkjet printer to, in essence, paint on certain layers.&ldquo;We&rsquo;ve engineered all of these layers and their active elements to work together flawlessly,&rdquo; said post-doctoral scholar Sihong Wang, co-lead author of the paper.The team has successfully fashioned its material in squares about two inches on a side containing more than 6,000 individual signal-processing devices that act like synthetic nerve endings. All this is encapsulated in a waterproof protective layer.The prototype can be stretched to double its original dimensions&mdash;and back again&mdash;all the while maintaining its ability to conduct electricity without cracks, delamination or wrinkles. To test durability, the team stretched a sample more than one thousand times without significant damage or loss of sensitivity. The real test came when the researchers adhered their sample to a human hand.&ldquo;It works great, even on irregularly shaped surfaces,&rdquo; said postdoctoral scholar Jie Xu, and the paper&rsquo;s other co-lead author.Perhaps most promising of all, the fabrication process described in this paper could become a platform for evaluating other stretchable electronic materials developed by other researchers that could one day begin to replace today&rsquo;s rigid electronics.Bao said much work lies ahead before these new materials and processes are as ubiquitous and capable as rigid silicon circuitry. First up, she said, her team must improve the electronic speed and performance of their prototype, but this is a promising step.&ldquo;I believe we&rsquo;re on the verge of a whole new world of electronics,&rdquo; Bao said.

A technical first could enable the creation of foldable, stretchable touchscreens. | Illustration by Stefani Billings

​Stanford researchers have set the stage for an evolution in electronics by taking the concept of ‘artificial skin’ to the next level.

Stretchable, touch-sensitive electronics

Implantation of a stent-like flow diverter can offer one option for less invasive treatment of brain aneurysms &ndash; bulges in blood vessels &ndash; but the procedure requires frequent monitoring while the vessels heal. Now, a multi-university research team has demonstrated proof-of-concept for a highly flexible and stretchable sensor that could be integrated with the flow diverter to monitor hemodynamics in a blood vessel without costly diagnostic procedures.The sensor, which uses capacitance changes to measure blood flow, could reduce the need for testing to monitor the flow through the diverter. Researchers, led by Georgia Tech, have shown that the sensor accurately measures fluid flow in animal blood vessels in vitro, and are working on the next challenge: wireless operation that could allow in vivo testing.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1571290181747-sensor_9577.jpg" style="width: 766px;" class="fr-fic fr-dib">Woon-Hong Yeo, an assistant professor in Georgia Tech&rsquo;s George W. Woodruff School of Mechanical Engineering and Wallace H. Coulter Department of Biomedical Engineering, holds a flow sensor on a stent backbone. (Credit: John Toon, Georgia Tech)&nbsp;The research was reported July 18 in the journal ACS Nano and was supported by multiple grants from Georgia Tech&rsquo;s Institute for Electronics and Nanotechnology, the University of Pittsburgh and the Korea Institute of Materials Science.&nbsp;&ldquo;The nanostructured sensor system could provide advantages for patients, including a less invasive aneurysm treatment and an active monitoring capability,&rdquo; said&nbsp;<a href="http://www.me.gatech.edu/faculty/yeo" target="_blank">Woon-Hong Yeo</a>, an assistant professor in Georgia Tech&rsquo;s&nbsp;<a href="http://www.me.gatech.edu/" target="_blank">George W. Woodruff School of Mechanical Engineering</a> and&nbsp;<a href="http://www.bme.gatech.edu/" target="_blank">Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University</a>. &ldquo;The integrated system could provide active monitoring of hemodynamics after surgery, allowing the doctor to follow up with quantitative measurement of how well the flow diverter is working in the treatment.&rdquo;Cerebral aneurysms occur in up to five percent of the population, with each aneurysm carrying a one percent risk per year of rupturing, noted Youngjae Chun, an associate professor in the Swanson School of Engineering at the University of Pittsburgh. Aneurysm rupture will cause death in up to half of affected patients.&nbsp;Endovascular therapy using platinum coils to fill the aneurysm sac has become the standard of care for most aneurysms, but recently a new endovascular approach &ndash; a flow diverter &ndash; has been developed to treat cerebral aneurysms. Flow diversion involves placing a porous stent across the neck of an aneurysm to redirect flow away from the sac, generating local blood clots within the sac.&ldquo;We have developed a highly stretchable, hyper-elastic flow diverter using a highly-porous thin film nitinol,&rdquo; Chun explained. &ldquo;None of the existing flow diverters, however, provide quantitative, real-time monitoring of hemodynamics within the sac of cerebral aneurysm. Through the collaboration with Dr. Yeo&#39;s group at Georgia Tech, we have developed a smart flow-diverter system that can actively monitor the flow alterations during and after surgery.&rdquo; &nbsp;Repairing the damaged artery takes months or even years, during which the flow diverter must be monitored using MRI and angiogram technology, which is costly and involves injection of a magnetic dye into the blood stream. Yeo and his colleagues hope their sensor could provide simpler monitoring in a doctor&rsquo;s office using a wireless inductive coil to send electromagnetic energy through the sensor. By measuring how the energy&rsquo;s resonant frequency changes as it passes through the sensor, the system could measure blood flow changes into the sac.&ldquo;We are trying to develop a batteryless, wireless device that is extremely stretchable and flexible that can be miniaturized enough to be routed through the tiny and complex blood vessels of the brain and then deployed without damage,&rdquo; said Yeo. &ldquo;It&rsquo;s a very challenging to insert such electronic system into the brain&rsquo;s narrow and contoured blood vessels.&rdquo;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1571290214140-sensor_0903.jpg" style="width: 753px;" class="fr-fic fr-dib">With gloved fingers for scale, a proof-of-concept flow sensor is shown here on a stent backbone. (Credit: Woon-Hong Yeo, Georgia Tech) The sensor uses a micro-membrane made of two metal layers surrounding a dielectric material, and wraps around the flow diverter. The device is just a few hundred nanometers thick, and is produced using nanofabrication and material transfer printing techniques, encapsulated in a soft elastomeric material.&ldquo;The membrane is deflected by the flow through the diverter, and depending on the strength of the flow, the velocity difference, the amount of deflection changes,&rdquo; Yeo explained. &ldquo;We measure the amount of deflection based on the capacitance change, because the capacitance is inversely proportional to the distance between two metal layers.&rdquo;Because the brain&rsquo;s blood vessels are so small, the flow diverters can be no more than five to ten millimeters long and a few millimeters in diameter. That rules out the use of conventional sensors with rigid and bulky electronic circuits.&ldquo;Putting functional materials and circuits into something that size is pretty much impossible right now,&rdquo; Yeo said. &ldquo;What we are doing is very challenging based on conventional materials and design strategies.&rdquo;The researchers tested three materials for their sensors: gold, magnesium and the nickel-titanium alloy known as nitinol. All can be safely used in the body, but magnesium offers the potential to be dissolved into the bloodstream after it is no longer needed.The proof-of-principle sensor was connected to a guide wire in the in vitro testing, but Yeo and his colleagues are now working on a wireless version that could be implanted in a living animal model. While implantable sensors are being used clinically to monitor abdominal blood vessels, application in the brain creates significant challenges.&ldquo;The sensor has to be completely compressed for placement, so it must be capable of stretching 300 or 400 percent,&rdquo; said Yeo. &ldquo;The sensor structure has to be able to endure that kind of handling while being conformable and bending to fit inside the blood vessel.&rdquo;

A proof-of-concept flow sensor is shown here on a stent backbone. (Credit: John Toon, Georgia Tech)

Implantation of a stent-like flow diverter can offer one option for less invasive treatment of brain aneurysms – bulges in blood vessels – but the procedure requires frequent monitoring while the vessels heal.

Integrated Sensor Could Monitor Brain Aneurysm Treatment

Infrared spectroscopy is the benchmark method for detecting and analyzing organic compounds. But it requires complicated procedures and large, expensive instruments, making device miniaturization challenging and hindering its use for some industrial and medical applications and for data collection out in the field, such as for measuring pollutant concentrations. Furthermore, it is fundamentally limited by low sensitivities and therefore requires large sample amounts.However, scientists at EPFL&rsquo;s School of Engineering and at Australian National University (ANU) have developed a compact and sensitive nanophotonic system that can identify a molecule&rsquo;s absorption characteristics without using conventional spectrometry. The scientists have already used their system to detect polymers, pesticides and organic compounds. What&rsquo;s more, it is compatible with CMOS technology.Their system consists of an engineered surface covered with hundreds of tiny sensors called metapixels, which can generate a distinct bar code for every molecule that the surface comes into contact with. These bar codes can be massively analyzed and classified using advanced pattern recognition and sorting technology such as artificial neural networks. This research &ndash; which sits at the crossroads of physics, nanotechnology and big data &ndash; has been published in&nbsp;Science.Translating molecules into bar codes The chemical bonds in organic molecules each have a specific orientation and vibrational mode. It influences the way molecules absorb light, giving each one a unique &ldquo;signature.&rdquo; Infrared spectroscopy detects whether a given molecule is present in a sample by seeing if the sample absorbs light rays at the molecule&rsquo;s signature frequencies. However, such analyses require lab instruments with a hefty size and price tag.The pioneering system developed by the EPFL scientists is both highly sensitive and capable of being miniaturized; it uses nanostructures that can trap light on the nanoscale and thereby provide very high detection levels for samples on the surface. &ldquo;The molecules we want to detect are nanometric in scale, so bridging this size gap is an essential step,&rdquo; says Hatice Altug, head of EPFL&rsquo;s&nbsp;<a href="https://bios.epfl.ch/" target="_blank">BioNanoPhotonic Systems Laboratory</a> and a coauthor of the study.The system&rsquo;s nanostructures are grouped into what are called metapixels so that each one resonates at a different frequency. When a molecule comes into contact with the surface, the way the molecule absorbs light changes the behavior of all the metapixels it touches.&ldquo;Importantly, the metapixels are arranged in such a way that different vibrational frequencies are mapped to different areas on the surface,&rdquo; says Andreas Tittl, lead author of the study.This creates a pixelated map of light absorption that can be translated into a molecular bar code &ndash; all without using a spectrometer.&ldquo;Thanks to our sensors&rsquo; unique optical properties, we can generate bar codes even with broadband light sources and detectors,&rdquo; says Aleksandrs Leitis, a coauthor of the study.There are a number of potential applications for this new system. &ldquo;For instance, it could be used to make portable medical testing devices that generate bar codes for each of the biomarkers found in a blood sample,&rdquo; says Dragomir Neshev, another coauthor of the study.Artificial intelligence could be used in conjunction with this new technology to create and process a whole library of molecular bar codes for compounds ranging from protein and DNA to pesticides and polymers. That would give researchers a new tool for quickly and accurately spotting miniscule amounts of compounds present in complex samples.

A new system developed at EPFL can detect and analyze molecules with very high precision and without needing bulky equipment. It opens the door to large-scale, image-based detection of materials aided by artificial intelligence. The research has been published in Science.

Infrared spectroscopy is the benchmark method for detecting and analyzing organic compounds.

A nanotech sensor turns molecular fingerprints into bar codes

An array of silver-TPU ink sensors printed on a flexible TPU base. (Image courtesy of the Wyss Institute for Biologically Inspired Engineering)

artificial skin sensors

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