Category Archives: wearable electronics

Transforming lithium-ion battery electrodes into wearable, fabric-based, flexible, and stretchable electrodes

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There’s a long road before this technology can be commercialized but the news seems promising. From a July 26, 2023 University of Houston news release (also on EurekAlert) by Rashda Khan, Note: Links have been removed,

Most people already know and appreciate the capabilities of smart phones, now imagine the possibilities offered by smart spacesuits, uniforms and exercise clothes. The future of wearable technology just got a big boost thanks to a team of University of Houston researchers who designed, developed and delivered a successful prototype of a fully stretchable fabric-based lithium-ion battery.

The idea for this cutting-edge evolution of the lithium-ion battery came from the mind of Haleh Ardebili, Bill D. Cook Professor of Mechanical Engineering at UH. “As a big science fiction fan, I could envision a ‘science-fiction-esque future’ where our clothes are smart, interactive and powered,” she said. “It seemed a natural next step to create and integrate stretchable batteries with stretchable devices and clothing. Imagine folding or bending or stretching your laptop or phone in your pocket. Or using interactive sensors embedded in our clothes that monitor our health.”

Some of these ideas are already becoming a reality. However, like all electronics, they need power, which is where the stretchable and flexible batteries come in. A major bottleneck in the development of the next generation of electronics or wearable technology embedded in fabrics is that conventional batteries are generally rigid, which limits functionality of the items, and they use a liquid electrolyte, which raises safety concerns. The traditional organic liquid electrolytes are flammable and can lead to the possibility of the batteries catching fire or even exploding under certain conditions.

The key to the UH research team’s breakthrough lies in the researchers using conductive silver fabric as a platform and current collector.

“The weaved silver fabric was ideal for this since it mechanically deforms or stretches and still provides electrical conduction pathways necessary for the battery electrode to function well. The battery electrode must allow movement of both electrons and ions,” said Ardebili, who is the corresponding author of a paper detailing this research in the Extreme Mechanics Letters. The first author of the paper is Bahar Moradi Ghadi, a former doctoral student who based her dissertation on this research.

By transforming rigid lithium-ion battery electrodes into wearable, fabric-based, flexible, and stretchable electrodes, this technology opens up exciting possibilities by offering stable performance and safer properties for wearable devices and implantable biosensors.

How It All Started

The idea for stretchable batteries occurred to Ardebili several years ago.

“I was interested in understanding the fundamental science and mechanisms related to stretching an electrochemical cell and its components,” she said. “This was an unexplored field in science and engineering and a great area to investigate.”

The science of coupling effects of mechanical deformation and electrochemical performance is an important field and stretchable batteries provide a great vehicle for exploring the fundamental mechanisms.

Ardebili developed her ideas into grant proposals and won several key awards to support her work, including a five-year National Science Foundation CAREER Award in 2013, a New Investigator Award from the NASA Texas Space Center Grant Consortium in 2014 and an award from the US Army Research Lab (ARL) in 2017.

“Although we have created a prototype, we are still working on optimizing the battery design, materials and fabrication,” said Ardebili.

What Is Next

Ardebili is optimistic that the prototype for a stretchable fabric-based battery will pave the way for many types of applications such as smart space suits, consumer electronics embedded in garments that monitor people’s health and devices that interact with humans at various levels. There are many possible designs and applications for safe, light, flexible and stretchable batteries, but there is still some work to be done before they are available on the market.

“Commercial viability depends on many factors such as scaling up the manufacturability of the product, cost and other factors,” she said. “We are working toward those considerations and goals as we optimize and enhance our stretchable battery.”

Whether the stretchy batteries end up powering spacesuits or workout clothes or some other innovative application, Ardebili wants them to be reliable and safe. “My goal is to make sure the batteries are as safe as possible [emphasis mine],” she said.

I’m glad to see safety is mentioned since there have been issues with lithium-ion batteries bursting into flame. (My last piece on research into making lithium-ion batteries safer is a January 13, 2016 post. There’s a more recent piece in the IEEE’s Spectrum magazine, an August 23, 2018 article by Weiyang Li and Yi Cui)

Getting back to the latest, here’s a link to and a citation for the paper,

Stretchable fabric-based lithium-ion battery by Bahar Moradi Ghadi, Banafsheh Hekmatnia, Qiang Fu, and Haleh Ardebili. Extreme Mechanics Letters
Volume 61, June 2023, 102026 DOI: https://doi.org/10.1016/j.eml.2023.102026

This paper is behind a paywall.

100-fold increase in AI energy efficiency

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Most people don’t realize how much energy computing, streaming video, and other technologies consume and AI (artificial intelligence) consumes a lot. (For more about work being done in this area, there’s my October 13, 2023 posting about an upcoming ArtSci Salon event in Toronto featuring Laura U. Marks’s recent work ‘Streaming Carbon Footprint’ and my October 16, 2023 posting about how much water is used for AI.)

So this news is welcome, from an October 12, 2023 Northwestern University news release (also received via email and on EurekAlert), Note: Links have been removed,

AI just got 100-fold more energy efficient

Nanoelectronic device performs real-time AI classification without relying on the cloud

– AI is so energy hungry that most data analysis must be performed in the cloud
– New energy-efficient device enables AI tasks to be performed within wearables
– This allows real-time analysis and diagnostics for faster medical interventions
– Researchers tested the device by classifying 10,000 electrocardiogram samples
– The device successfully identified six types of heart beats with 95% accuracy

Northwestern University engineers have developed a new nanoelectronic device that can perform accurate machine-learning classification tasks in the most energy-efficient manner yet. Using 100-fold less energy than current technologies, the device can crunch large amounts of data and perform artificial intelligence (AI) tasks in real time without beaming data to the cloud for analysis.

With its tiny footprint, ultra-low power consumption and lack of lag time to receive analyses, the device is ideal for direct incorporation into wearable electronics (like smart watches and fitness trackers) for real-time data processing and near-instant diagnostics.

To test the concept, engineers used the device to classify large amounts of information from publicly available electrocardiogram (ECG) datasets. Not only could the device efficiently and correctly identify an irregular heartbeat, it also was able to determine the arrhythmia subtype from among six different categories with near 95% accuracy.

The research was published today (Oct. 12 [2023]) in the journal Nature Electronics.

“Today, most sensors collect data and then send it to the cloud, where the analysis occurs on energy-hungry servers before the results are finally sent back to the user,” said Northwestern’s Mark C. Hersam, the study’s senior author. “This approach is incredibly expensive, consumes significant energy and adds a time delay. Our device is so energy efficient that it can be deployed directly in wearable electronics for real-time detection and data processing, enabling more rapid intervention for health emergencies.”

A nanotechnology expert, Hersam is Walter P. Murphy Professor of Materials Science and Engineering at Northwestern’s McCormick School of Engineering. He also is chair of the Department of Materials Science and Engineering, director of the Materials Research Science and Engineering Center and member of the International Institute of Nanotechnology. Hersam co-led the research with Han Wang, a professor at the University of Southern California, and Vinod Sangwan, a research assistant professor at Northwestern.

Before machine-learning tools can analyze new data, these tools must first accurately and reliably sort training data into various categories. For example, if a tool is sorting photos by color, then it needs to recognize which photos are red, yellow or blue in order to accurately classify them. An easy chore for a human, yes, but a complicated — and energy-hungry — job for a machine.

For current silicon-based technologies to categorize data from large sets like ECGs, it takes more than 100 transistors — each requiring its own energy to run. But Northwestern’s nanoelectronic device can perform the same machine-learning classification with just two devices. By reducing the number of devices, the researchers drastically reduced power consumption and developed a much smaller device that can be integrated into a standard wearable gadget.

The secret behind the novel device is its unprecedented tunability, which arises from a mix of materials. While traditional technologies use silicon, the researchers constructed the miniaturized transistors from two-dimensional molybdenum disulfide and one-dimensional carbon nanotubes. So instead of needing many silicon transistors — one for each step of data processing — the reconfigurable transistors are dynamic enough to switch among various steps.

“The integration of two disparate materials into one device allows us to strongly modulate the current flow with applied voltages, enabling dynamic reconfigurability,” Hersam said. “Having a high degree of tunability in a single device allows us to perform sophisticated classification algorithms with a small footprint and low energy consumption.”

To test the device, the researchers looked to publicly available medical datasets. They first trained the device to interpret data from ECGs, a task that typically requires significant time from trained health care workers. Then, they asked the device to classify six types of heart beats: normal, atrial premature beat, premature ventricular contraction, paced beat, left bundle branch block beat and right bundle branch block beat.

The nanoelectronic device was able to identify accurately each arrhythmia type out of 10,000 ECG samples. By bypassing the need to send data to the cloud, the device not only saves critical time for a patient but also protects privacy.

“Every time data are passed around, it increases the likelihood of the data being stolen,” Hersam said. “If personal health data is processed locally — such as on your wrist in your watch — that presents a much lower security risk. In this manner, our device improves privacy and reduces the risk of a breach.”

Hersam imagines that, eventually, these nanoelectronic devices could be incorporated into everyday wearables, personalized to each user’s health profile for real-time applications. They would enable people to make the most of the data they already collect without sapping power.

“Artificial intelligence tools are consuming an increasing fraction of the power grid,” Hersam said. “It is an unsustainable path if we continue relying on conventional computer hardware.”

…

Here’s a link to and a citation for the paper,

Reconfigurable mixed-kernel heterojunction transistors for personalized support vector machine classification by Xiaodong Yan, Justin H. Qian, Jiahui Ma, Aoyang Zhang, Stephanie E. Liu, Matthew P. Bland, Kevin J. Liu, Xuechun Wang, Vinod K. Sangwan, Han Wang & Mark C. Hersam. Nature Electronics (2023) DOI: https://doi.org/10.1038/s41928-023-01042-7 Published: 12 October 2023

This paper is behind a paywall.

Wearable screen (flexible display) from the University of British Columbia (UBC)

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If I read this correctly, the big selling point for UBC’s flexible, wearable display screen is energy efficiency. From a July 10, 2023 University of British Columbia (UBC) news release on EurekAlert,

Imagine a wearable patch that tracks your vital signs through changes in the colour display, or shipping labels that light up to indicate changes in temperature or sterility of food items.

These are among the potential uses for a new flexible display created by UBC researchers and announced recently in ACS Applied Materials and Interfaces.

“This device is capable of fast, realtime and reversible colour change,” says researcher Claire Preston, who developed the device as part of her master’s in electrical and computer engineering at UBC. “It can stretch up to 30 per cent without losing performance. It uses a colour-changing technology that can be used for visual monitoring. And it is relatively cheap to manufacture.”

Previous attempts at creating stretchable displays have involved complex designs and materials, limiting their stretchability and optical quality. In this new research, scientists leaned on electrochromic displays—which are able to reversibly change colour, while requiring low power consumption—to overcome these limitations. [emphasis mine]

“We used PEDOT:PSS, an electrochromic material that consists of a conductive polymer combined with an ionic liquid, resulting in a stretchable electrode that acts as both the electrochromic element and the ion storage layer. This simplifies the device’s architecture and eliminates the need for a separate stretchable conductor,” says Ms. Preston.

The display is transparent and feels like a stiff rubber band. To support the thin layers of PEDOT and allow them to elongate without breaking, the team added a solid polymer electrolyte and a stretchable encapsulation material called styrene-ethylene-butylene-styrene (SEBS).

“The potential uses for this stretchable display are significant. It could be integrated into wearable devices for biometric monitoring, allowing for real-time visual feedback on vital signs. The displays could also be used in robotic skin, enabling robots to display information and interact more intuitively with humans,” noted senior author Dr. John Madden, a professor of electrical and computer engineering who supervised the work.

Additionally, the low power consumption and cost-effectiveness of this technology make it attractive for use in disposable applications such as indicator patches for medical purposes or smart packaging labels for sensitive shipments. It could also be used to actively change the colour of jackets, hats and other garments.

“While there is need for more work to integrate this device into everyday devices, this breakthrough brings us one step closer to a future where flexible and stretchable displays are a common part of our daily lives,” Dr. Madden added.

Here’s a link to and a citation for the paper,

Intrinsically Stretchable Integrated Passive Matrix Electrochromic Display Using PEDOT:PSS Ionic Liquid Composite by Claire Preston, Yuta Dobashi, Ngoc Tan Nguyen, Mirza Saquib Sarwar, Daniel Jun, Cédric Plesse, Xavier Sallenave, Frédéric Vidal, Pierre-Henri Aubert, and John D. W. Madden. ACS Appl. Mater. Interfaces 2023, 15, 23, 28288–28299 DOI: https://doi.org/10.1021/acsami.3c02902 Publication Date: June 5, 2023 Copyright © 2023 The Authors. Published by American Chemical Society

This paper is open access.

Flexible keyboards and wearable sketchpads: all in a touch-responsive fabric armband

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Who doesn’t love a panda? It looks like someone is drawing on the armband with their fingers but the lines look a lot finer, more like a stylus was used.

Caption: When a person draws a panda on this touch-responsive armband that’s worn on their forearm (bottom right of photo), it shows up on a computer. Credit: Adapted from ACS Nano 2023, DOI: 10.1021/acsnano.2c12612

A May 2, 2023 news item on ScienceDaily announces the flexible armband,

It’s time to roll up your sleeves for the next advance in wearable technology — a fabric armband that’s actually a touch pad. In ACS [American Chemical Society] Nano, researchers say they have devised a way to make playing video games, sketching cartoons and signing documents easier. Their proof-of-concept silk armband turns a person’s forearm into a keyboard or sketchpad. The three-layer, touch-responsive material interprets what a user draws or types and converts it into images on a computer.

…

A May 2, 2023 American Chemical Society (ACS) news release (also on EurekAlert), which originated the news item, describes the work in more detail,

Computer trackpads and electronic signature-capture devices seem to be everywhere, but they aren’t as widely used in wearables. Researchers have suggested making flexible touch-responsive panels from clear, electrically conductive hydrogels, but these substances are sticky, making them hard to write on and irritating to the skin. So, Xueji Zhang, Lijun Qu, Mingwei Tian and colleagues wanted to incorporate a similar hydrogel into a comfortable fabric sleeve for drawing or playing games on a computer.

The researchers sandwiched a pressure-sensitive hydrogel between layers of knit silk. The top piece was coated in graphene nanosheets to make the fabric electrically conductive. Attaching the sensing panel to electrodes and a data collection system produced a pressure-responsive pad with real-time, rapid sensing when a finger slid over it, writing numbers and letters. The device was then incorporated into an arm-length silk sleeve with a touch-responsive area on the forearm. In experiments, a user controlled the direction of blocks in a computer game and sketched colorful cartoons in a computer drawing program from the armband. The researchers say that their proof-of-concept wearable touch panel could inspire the next generation of flexible keyboards and wearable sketchpads.       

Here’s a link to and a citation for the paper,

Skin-Friendly and Wearable Iontronic Touch Panel for Virtual-Real Handwriting Interaction by Ruidong Xu, Minghua She, Jiaxu Liu, Shikang Zhao, Jisheng Zhao, Xueji Zhang, Lijun Qu, and Mingwei Tian. ACS Nano 2023, 17, 9, 8293–8302 DOI: https://doi.org/10.1021/acsnano.2c12612 Publication Date: April 19, 2023 Copyright © 2023 American Chemical Society

This paper is behind a paywall.

Future firefighters and wearable technology

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I imagine this wearable technology would also be useful for the military too. However, the focus for these researchers from China is firefighting. (Given the situation with the Canadian wildfires in June 2023, we have 10x more than the average at this time in the season over the last 10 years, it’s good to see some work focused on safety for firefighters.) From a January 17, 2023 news item on phys.org,

Firefighting may look vastly different in the future thanks to intelligent fire suits and masks developed by multiple research institutions in China.

Researchers published results showing breathable electrodes woven into fabric used in fire suits have proven to be stable at temperatures over 520ºC. At these temperatures, the fabric is found to be essentially non-combustible with high rates of thermal protection time.

…

Caption: Scientists from multiple institutions address the challenges and limitations of current fire-fighting gear by introducing wearable, breathable sensors and electrodes to better serve firefighters. Credit: Nano Research, Tsinghua University Press

A January 17, 2023 Tsinghua University Press press release on EurekAlert, which originated the news item, provides more technical details,

The results show the efficacy and practicality of Janus graphene/poly(p-phenylene benzobisoxazole), or PBO, woven fabric in making firefighting “smarter” with the main goal being to manufacture products on an industrial scale that are flame-retardant but also intelligent enough to warn the firefighter of increased risks while traversing the flames.

“Conventional firefighting clothing and fire masks can ensure firemen’s safety to a certain extent,” said Wei Fan, professor at the School of Textile Science and Engineering at Xi’an Polytechnic University. “However, the fire scene often changes quickly, sometimes making firefighters trapped in the fire for failing to judge the risks in time. At this situation, firefighters also need to be rescued.”

The key here is the use of Janus graphene/PBO, woven fabrics. While not the first of its kind, the introduction of PBO fibers offers better strength and fire protection than other similar fibers, such as Kevlar. The PBO fibers are first woven into a fabric that is then irradiated using a CO2 infrared laser. From here, the fabric becomes the Janus graphene/PBO hybrid that is the focus of the study.   

The mask also utilizes a top and bottom layer of Janus graphene/PBO with a piezoelectric layer in between that acts as a way to convert mechanical pressures to electricity.

“The mask has a good smoke particle filtration effect, and the filtration efficiency of PM2.5 and PM3.0 reaches 95% and 100%, respectively. Meanwhile, the mask has good wearing comfort as its respiratory resistance (46.8 Pa) is lower than 49 Pa of commercial masks. Besides, the mask is sensitive to the speed and intensity of human breathing, which can dynamically monitor the health of the firemen” said Fan.

Flame-retardant electronics featured in these fire suits are flexible, heat resistant, quick to make and low-cost which makes scaling for industrial production a tangible achievement. This makes it more likely that the future of firefighting suits and masks will be able to effectively use this technology. Quick, effective responses can also reduce economic losses attributed to fires.

“The graphene/PBO woven fabrics-based sensors exhibit good repeatability and stability in human motion monitoring and NO2 gas detection, the main toxic gas in fires, which can be applied to firefighting suits to help firefighters effectively avoiding danger” Fan said. Being able to detect sharp increases in NO2 gas can help firefighters change course in an instant if needed and could be a lifesaving addition to firefighter gear.

Major improvements can be made in the firefighting field to better protect the firefighters by taking advantage of graphene/PBO woven and nonwoven fabrics. Widescale use of this technology can help the researchers reach their ultimate goal of reducing mortality and injury to those who risk their lives fighting fires.

Yu Luo and Yaping Miao of the School of Textile Science and Engineering at Xi’an Polytechnic University contributed equally to this work. Professor Wei Fan is the corresponding author. Yingying Zhang and Huimin Wang of the Department of Chemistry at Tsinghua University, Kai Dong of the Beijing Institute of Nanoenergy and Nanosystems at the Chinese Academy of Sciences, and Lin Hou and Yanyan Xu of Shaanxi Textile Research Institute Co., LTD, Weichun Chen and Yao Zhang of the School of Textile Science and Engineering at Xi’an Polytechnic University contributed to this research. 

This work was supported by the National Natural Science Foundation of China, Textile Vision Basic Research Program of China, Key Research and Development Program of Xianyang Science and Technology Bureau, Key Research and Development Program of Shaanxi Province, Natural Science Foundation of Shaanxi Province, and Scientific Research Project of Shaanxi Provincial Education Department.

Here are two links and a citation for the same paper,

Laser-induced Janus graphene/poly(p-phenylene benzobisoxazole) fabrics with intrinsic flame retardancy as flexible sensors and breathable electrodes for fire-fighting field by Yu Luo, Yaping Miao, Huimin Wang, Kai Dong, Lin Hou, Yanyan Xu, Weichun Chen, Yao Zhang, Yingying Zhang & Wei Fan. Nano Research (2023) DOI: https://doi.org/10.1007/s12274-023-5382-y Published12 January 2023

This link leads to a paywall.

Here’s the second link (to SciOpen)

Laser-induced Janus graphene/poly(p-phenylene benzobisoxazole) fabrics with intrinsic flame retardancy as flexible sensors and breathable electrodes for fire-fighting field. SciOpen Published January 12, 2023

This link leads to an open access journal published by Tsinghua University Press.

Embroidery as a low-cost solution for making wearable electronics?

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A November 22, 2022 news item on Nanowerk explores embroidery as a means for affixing wearable electronics to textiles,

Embroidering power-generating yarns onto fabric allowed researchers to embed a self-powered, numerical touch-pad and movement sensors into clothing. The technique offers a low-cost, scalable potential method for making wearable devices.

“Our technique uses embroidery, which is pretty simple – you can stitch our yarns directly on the fabric,” said the study’s lead author Rong Yin, assistant professor of textile engineering, chemistry and science at North Carolina State University. “During fabric production, you don’t need to consider anything about the wearable devices. You can integrate the power-generating yarns after the clothing item has been made.”

…

Caption: Yu Chen, graduate student at NC State, demonstrates embroidery techniques. Courtesy: North Caroline State University

A North Carolina State University November 22, 2022 news release (also on EurekAlert), which originated the news item, describes the research in more detail,

In the study published in Nano Energy, researchers tested multiple designs for power-generating yarns. To make them durable enough to withstand the tension and bending of the embroidery stitching process, they ultimately used five commercially available copper wires, which had a thin polyurethane coating, together. Then, they stitched them onto cotton fabric with another material called PTFE.

“This is a low-cost method for making wearable electronics using commercially available products,” Yin said. “The electrical properties of our prototypes were comparable to other designs that relied on the same power generation mechanism.”

The researchers relied on a method of generating electricity called the “triboelectric effect,” which involves harnessing electrons exchanged by two different materials, like static electricity. They found the PTFE fabric had the best performance in terms of voltage and current when in contact with the polyurethane-coated copper wires, as compared to other types of fabric that they tested, including cotton and silk. They also tested coating the embroidery samples in plasma to increase the effect.

In our design, you have two layers – one is your conductive, polyurethane-coated copper wires, and the other is PTFE, and they have a gap between them,” Yin said. “When the two non-conductive materials come into contact with each other, one material will lose some electrons, and some will get some electrons. When you link them together, there will be a current.”

Researchers tested their yarns as motion sensors by embroidering them with the PTFE fabric on denim. They placed the embroidery patches on the palm, under the arm, at the elbow and at the knee to track electrical signals generated as a person moves. They also attached fabric with their embroidery on the insole of a shoe to test its use as a pedometer, finding their electrical signals varied depending on whether the person was walking, running or jumping.

Lastly, they tested their yarns in a textile-based numeric keypad on the arm, which they made by embroidering numbers on a piece of cotton fabric, and attaching them to a piece of PTFE fabric. Depending on the number that the person pushed on the keypad, they saw different electrical signals generated for each number.

“You can embroider our yarns onto clothes, and when you move, it generates an electrical signal, and those signals can be used as a sensor,” Yin said. “When we put the embroidery in a shoe, if you are running, it generates a higher voltage than if you were just walking. When we stitched numbers onto fabric, and press them, it generates a different voltage for each number. It could be used as an interface.”

Since textile products will inevitably be washed, they tested the durability of their embroidery design in a series of washing and rubbing tests. After hand washing and rinsing the embroidery with detergent, and drying it in an oven, they found no difference or a slight increase in voltage. For the prototype coated in plasma, they found weakened but still superior performance compared with the original sample. After an abrasion test, they found that there was no significant change in electrical output performance of their designs after 10,000 rubbing cycles.

In future work, they plan to integrate their sensors with other devices to add more functions.

“The next step is to integrate these sensors into a wearable system,” Yin said.

Here’s a link to and a citation for the paper,

Flexible, durable, and washable triboelectric yarn and embroidery for self-powered sensing and human-machine interaction by Yu Chen, Erdong Chen, Zihao Wang, Yali Ling, Rosie Fisher, Mengjiao Li, Jacob Hart, Weilei Mu, Wei Gao, Xiaoming Tao, Bao Yang and Rong Yin. Nano Energy Volume 104, Part A, 15 December 2022, 107929 DOI: 10.1016/j.nanoen.2022.107929 Available online: 27 October 2022 Version of Record: 4 November 2022.

This paper is behind a paywall.

SkinKit: smart tattoo provides on-skin computing

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The SkinKit wearable sensing interface, developed in the Hybrid Body Lab, can be used for health and wellness, personal safety, as assistive technology and for athletic training, among many applications. Hybrid Body Lab/Provided

A November 3, 2022 Cornell University news release on EurekAlert announces a computer you can attach to your skin (Note: Links have been removed),

Researchers at Cornell University have come up with a reliable, skin-tight computing system that’s easy to attach and detach, and can be used for a variety of purposes – from health monitoring to fashion.

On-skin interfaces – sometimes known as “smart tattoos” – have the potential to outperform the sensing capabilities of current wearable technologies but combining comfort and durability has proven challenging.

“We’ve been working on this for years,” said Cindy (Hsin-Liu) Kao, assistant professor of human centered design, and the study’s senior author, “and I think we’ve finally figured out a lot of the technical challenges. We wanted to create a modular approach to smart tattoos, to make them as straightforward as building Legos.”

SkinKit – a plug-and-play system that aims to “lower the floor for entry” to on-skin interfaces for those with little or no technical expertise – is the product of countless hours of development, testing and redevelopment, Kao said. Fabrication is done with temporary tattoo paper, silicone textile stabilizer and water, creating a multi-layer thin film structure they call “skin cloth.” The layered material can be cut into desired shapes and fitted with electronics hardware to perform a range of tasks.

“The wearer can easily attach them together and also detach them,” said Pin-Sung Ku, lead author of the paper and Hybrid Body Lab member. “Let’s say that today you want to use one of the sensors for certain purposes, but tomorrow you want it for something different. You can easily just detach them and reuse some of the modules to make a new device in minutes.”

The paper “SkinKit: Construction Kit for On-Skin Interface Prototyping” was presented at UbiComp ’22, the Association for Computing Machinery’s international joint conference on pervasive and ubiquitous computing.

Here’s a SkinKit video provided by Cornell University’s Hybrid Body Lab,

Tom Fleischman’s November 3, 2022 story for the Cornell Chronicle provides more details about SkinKit (Note: Links have been removed),

SkinKit – a plug-and-play system that aims to “lower the floor for entry” to on-skin interfaces, Kao said, for those with little or no technical expertise – is the product of countless hours of development, testing and redevelopment, she said.

Kao’s lab is also very conscious of cultural differences generally, and she thinks it’s important to bring these devices to diverse populations.

“People from different cultures, backgrounds and ethnicities can have very different perceptions toward these devices,” she said. “We felt it’s actually very important to let more people have a voice in saying what they want these smart tattoos to do.”

…

To test SkinKit, the researchers first recruited nine participants with both STEM and design backgrounds to build and wear the devices. Their input from the 90-minute workshop helped inform further modifications, which the group performed before conducting a larger, two-day study involving 25 participants with both STEM and design backgrounds.

Devices designed by the 25 study participants addressed: health and wellness, including temperature sensors to detect fever due to COVID-19; personal safety, including a device that would help the wearer maintain social distance during the pandemic; notification, including an arm-worn device that a runner could wear that would vibrate when a vehicle was near; and assistive technology, such as a wrist-worn sensor for the blind that would vibrate when the wearer was about to bump into an object.

…

Kao said members of her lab, including Ku, took part in the 4-H Career Explorations Conference over the summer, and had approximately 10 middle-schoolers from upstate New York build their own SkinKit devices.

“I think it just shows us a lot of potential for STEM [science, technology, engineering, and mathematics] learning, and especially to be able to engage people who maybe originally wouldn’t have interest in STEM,” Kao said. “But by combining it with body art and fashion, I think there’s a lot of potential for it to engage the next generation and broader populations to explore the future of smart tattoos.”

…

Here’s a citation for the paper,

“SkinKit: Construction Kit for On-Skin Interface Prototyping” by Pin-Sung Ku, Md. Tahmidul Islam Molla, Kunpeng Huang, Priya Kattappurath, Krithik Ranjan, Hsin-Liu Cindy Kao. Proceedings of the ACM [Aossciation for Computing Machinery] on Interactive, Mobile, Wearable and Ubiquitous Technologies Volume 5 Issue 4 Dec 2021 Article No.: 165pp 1–23 DOI: https://doi.org/10.1145/3494989 Published: 30 December 2021

This paper is behind a paywall.

The Hybrid Body Lab can be found here (the pictures are fascinating). Here’s more from their About page,

The Hybrid Body Lab at Cornell University, founded and directed by Prof. Cindy Hsin-Liu Kao, focuses on the invention of culturally-inspired materials, processes, and tools for crafting technology on the body surface. Designing across scales, we explore how body scale interfaces can enhance our relations with everyday products and both natural and man-made environments. We conduct research at the intersection of Human-Computer Interaction, Wearable & Ubiquitous Computing, Digital Fabrication, Interaction Design, and Fashion & Body Art. We synthesize this knowledge to contribute a culturally-sensitive lens to the future of designs that interface the body and the environment. Our current investigations include:

Wearable Technology & On-Skin Interfaces
We develop novel wearable interfaces and fabrication processes, which a focus on skin-conformable or textile-based form factors. By hybridizing miniaturized robotics, machines, and materials with cultural body decoration practices, we investigate how technology can be situated as a culturally meaningful material for crafting our identities.

Designing Skins Across Scales
‘Many different types of machines that were parts of architecture have become parts of our bodies.’ —Bill Mitchell, Me++

We design “skins” that can be adapted across scales, from the architectural to the body scale. We investigate the interactions of a wearer’s body-borne interface with its surrounding ecology. This includes its interaction with other people, objects, to environments. We are also interested in developing skins that can be deployed across scales — from the body to the architectural scale.

Understanding Social Perceptions Towards On-Body Technologies
Wearable devices have evolved towards intrinsic human augmentation, unlocking the human skin as an interface for seamless interaction. However, the non-traditional form factor of these on-skin interfaces may raise concerns for public wear. These perceptions will influence whether a new form of technology will eventually be accepted, or rejected by society.  We investigate the cultural and social concerns that need to be considered when generating on-body technologies for inclusive design.

Bioinspired ‘smart’ materials a step towards soft robotics and electronics

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An October 13, 2022 news item on Nanowerk describes some new work from the University of Texas at Austin,

Inspired by living things from trees to shellfish, researchers at The University of Texas at Austin set out to create a plastic much like many life forms that are hard and rigid in some places and soft and stretchy in others.

Their success — a first, using only light and a catalyst to change properties such as hardness and elasticity in molecules of the same type — has brought about a new material that is 10 times as tough as natural rubber and could lead to more flexible electronics and robotics.

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An October 13, 2022 University of Texas at Austin news release (also on EurekAlert), which originated the news item, delves further into the work,

“This is the first material of its type,” said Zachariah Page, assistant professor of chemistry and corresponding author on the paper. “The ability to control crystallization, and therefore the physical properties of the material, with the application of light is potentially transformative for wearable electronics or actuators in soft robotics.”

Scientists have long sought to mimic the properties of living structures, like skin and muscle, with synthetic materials. In living organisms, structures often combine attributes such as strength and flexibility with ease. When using a mix of different synthetic materials to mimic these attributes, materials often fail, coming apart and ripping at the junctures between different materials.

Oftentimes, when bringing materials together, particularly if they have very different mechanical properties, they want to come apart,” Page said. Page and his team were able to control and change the structure of a plastic-like material, using light to alter how firm or stretchy the material would be.

Chemists started with a monomer, a small molecule that binds with others like it to form the building blocks for larger structures called polymers that were similar to the polymer found in the most commonly used plastic. After testing a dozen catalysts, they found one that, when added to their monomer and shown visible light, resulted in a semicrystalline polymer similar to those found in existing synthetic rubber. A harder and more rigid material was formed in the areas the light touched, while the unlit areas retained their soft, stretchy properties.

Because the substance is made of one material with different properties, it was stronger and could be stretched farther than most mixed materials.

The reaction takes place at room temperature, the monomer and catalyst are commercially available, and researchers used inexpensive blue LEDs as the light source in the experiment. The reaction also takes less than an hour and minimizes use of any hazardous waste, which makes the process rapid, inexpensive, energy efficient and environmentally benign.

The researchers will next seek to develop more objects with the material to continue to test its usability.

“We are looking forward to exploring methods of applying this chemistry towards making 3D objects containing both hard and soft components,” said first author Adrian Rylski, a doctoral student at UT Austin.

The team envisions the material could be used as a flexible foundation to anchor electronic components in medical devices or wearable tech. In robotics, strong and flexible materials are desirable to improve movement and durability.

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Here’s a link to and a citation for the paper,

Polymeric multimaterials by photochemical patterning of crystallinity by Adrian K. Rylski, Henry L. Cater, Keldy S. Mason, Marshall J. Allen, Anthony J. Arrowood, Benny D. Freeman, Gabriel E. Sanoja, and Zachariah A. Page. Science 13 Oct 2022 Vol 378, Issue 6616 pp. 211-215 DOI: 10.1126/science.add6975

This paper is behind a paywall.

Enhance or weaken memory with stretchy, bioinspired synaptic transistor

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This news is intriguing since they usually want to enhance memory not weaken it. Interestingly, this October 3, 2022 news item on ScienceDaily doesn’t immediately answer why you might want to weaken memory,

Robotics and wearable devices might soon get a little smarter with the addition of a stretchy, wearable synaptic transistor developed by Penn State engineers. The device works like neurons in the brain to send signals to some cells and inhibit others in order to enhance and weaken the devices’ memories.

Led by Cunjiang Yu, Dorothy Quiggle Career Development Associate Professor of Engineering Science and Mechanics and associate professor of biomedical engineering and of materials science and engineering, the team designed the synaptic transistor to be integrated in robots or wearables and use artificial intelligence to optimize functions. The details were published on Sept. 29 [2022] in Nature Electronics.

“Mirroring the human brain, robots and wearable devices using the synaptic transistor can use its artificial neurons to ‘learn’ and adapt their behaviors,” Yu said. “For example, if we burn our hand on a stove, it hurts, and we know to avoid touching it next time. The same results will be possible for devices that use the synaptic transistor, as the artificial intelligence is able to ‘learn’ and adapt to its environment.”

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A September 29, 2022 Pennsylvania State University (Penn State) news release (also on EurekAlert but published on October 3, 2022) by Mariah Chuprinski, which originated the news item, explains why you might want to weaken memory,

According to Yu, the artificial neurons in the device were designed to perform like neurons in the ventral tegmental area, a tiny segment of the human brain located in the uppermost part of the brain stem. Neurons process and transmit information by releasing neurotransmitters at their synapses, typically located at the neural cell ends. Excitatory neurotransmitters trigger the activity of other neurons and are associated with enhancing memories, while inhibitory neurotransmitters reduce the activity of other neurons and are associated with weakening memories.

“Unlike all other areas of the brain, neurons in the ventral tegmental area are capable of releasing both excitatory and inhibitory neurotransmitters at the same time,” Yu said. “By designing the synaptic transistor to operate with both synaptic behaviors simultaneously, fewer transistors are needed [emphasis mine] compared to conventional integrated electronics technology, which simplifies the system architecture and allows the device to conserve energy.”

To model soft, stretchy biological tissues, the researchers used stretchable bilayer semiconductor materials to fabricate the device, allowing it to stretch and twist while in use, according to Yu. Conventional transistors, on the other hand, are rigid and will break when deformed.

“The transistor is mechanically deformable and functionally reconfigurable, yet still retains its functions when stretched extensively,” Yu said. “It can attach to a robot or wearable device to serve as their outermost skin.”

In addition to Yu, other contributors include Hyunseok Shim and Shubham Patel, Penn State Department of Engineering Science and Mechanics; Yongcao Zhang, the University of Houston Materials Science and Engineering Program; Faheem Ershad, Penn State Department of Biomedical Engineering and University of Houston Department of Biomedical Engineering; Binghao Wang, School of Electronic Science and Engineering, Southeast University [Note: There’s one in Bangladesh, one in China, and there’s a Southeastern University in Florida, US] and Department of Chemistry and the Materials Research Center, Northwestern University; Zhihua Chen, Flexterra Inc.; Tobin J. Marks, Department of Chemistry and the Materials Research Center, Northwestern University; Antonio Facchetti, Flexterra Inc. and Northwestern University’s Department of Chemistry and Materials Research Center.

Here’s a link to and a citation for the paper,

An elastic and reconfigurable synaptic transistor based on a stretchable bilayer semiconductor by Hyunseok Shim, Faheem Ershad, Shubham Patel, Yongcao Zhang, Binghao Wang, Zhihua Chen, Tobin J. Marks, Antonio Facchetti & Cunjiang Yu. Nature Electronics (2022) DOI: DOI: https://doi.org/10.1038/s41928-022-00836-5 Published: 29 September 2022

This paper is behind a paywall.

Skin-like computing device analyzes health data with brain-mimicking artificial intelligence (a neuromorphic chip)

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The wearable neuromorphic chip, made of stretchy semiconductors, can implement artificial intelligence (AI) to process massive amounts of health information in real time. Above, Asst. Prof. Sihong Wang shows a single neuromorphic device with three electrodes. (Photo by John Zich)

Does everything have to be ‘brainy’? Read on for the latest on ‘brainy’ devices.

An August 4, 2022 University of Chicago news release (also on EurekAlert) describes work on a stretchable neuromorphic chip, Note: Links have been removed,

It’s a brainy Band-Aid, a smart watch without the watch, and a leap forward for wearable health technologies. Researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME) have developed a flexible, stretchable computing chip that processes information by mimicking the human brain. The device, described in the journal Matter, aims to change the way health data is processed.

“With this work we’ve bridged wearable technology with artificial intelligence and machine learning to create a powerful device which can analyze health data right on our own bodies,” said Sihong Wang, a materials scientist and Assistant Professor of Molecular Engineering.

Today, getting an in-depth profile about your health requires a visit to a hospital or clinic. In the future, Wang said, people’s health could be tracked continuously by wearable electronics that can detect disease even before symptoms appear. Unobtrusive, wearable computing devices are one step toward making this vision a reality. 

A Data Deluge
The future of healthcare that Wang—and many others—envision includes wearable biosensors to track complex indicators of health including levels of oxygen, sugar, metabolites and immune molecules in people’s blood. One of the keys to making these sensors feasible is their ability to conform to the skin. As such skin-like wearable biosensors emerge and begin collecting more and more information in real-time, the analysis becomes exponentially more complex. A single piece of data must be put into the broader perspective of a patient’s history and other health parameters.

Today’s smart phones are not capable of the kind of complex analysis required to learn a patient’s baseline health measurements and pick out important signals of disease. However, cutting-edge artificial intelligence platforms that integrate machine learning to identify patterns in extremely complex datasets can do a better job. But sending information from a device to a centralized AI location is not ideal.

“Sending health data wirelessly is slow and presents a number of privacy concerns,” he said. “It is also incredibly energy inefficient; the more data we start collecting, the more energy these transmissions will start using.”

Skin and Brains
Wang’s team set out to design a chip that could collect data from multiple biosensors and draw conclusions about a person’s health using cutting-edge machine learning approaches. Importantly, they wanted it to be wearable on the body and integrate seamlessly with skin.

“With a smart watch, there’s always a gap,” said Wang. “We wanted something that can achieve very intimate contact and accommodate the movement of skin.”

Wang and his colleagues turned to polymers, which can be used to build semiconductors and electrochemical transistors but also have the ability to stretch and bend. They assembled polymers into a device that allowed the artificial-intelligence-based analysis of health data. Rather than work like a typical computer, the chip— called a neuromorphic computing chip—functions more like a human brain, able to both store and analyze data in an integrated way.

Testing the Technology
To test the utility of their new device, Wang’s group used it to analyze electrocardiogram (ECG) data representing the electrical activity of the human heart. They trained the device to classify ECGs into five categories—healthy or four types of abnormal signals. Then, they tested it on new ECGs. Whether or not the chip was stretched or bent, they showed, it could accurately classify the heartbeats.

More work is needed to test the power of the device in deducing patterns of health and disease. But eventually, it could be used either to send patients or clinicians alerts, or to automatically tweak medications.

“If you can get real-time information on blood pressure, for instance, this device could very intelligently make decisions about when to adjust the patient’s blood pressure medication levels,” said Wang. That kind of automatic feedback loop is already used by some implantable insulin pumps, he added.

He already is planning new iterations of the device to both expand the type of devices with which it can integrate and the types of machine learning algorithms it uses.

“Integration of artificial intelligence with wearable electronics is becoming a very active landscape,” said Wang. “This is not finished research, it’s just a starting point.”

Here’s a link to and a citation for the paper,

Intrinsically stretchable neuromorphic devices for on-body processing of health data with artificial intelligence by Shilei Dai, Yahao Dai, Zixuan Zhao, Jie Xu, Jia Huang, Sihong Wang. Matter DOI:https://doi.org/10.1016/j.matt.2022.07.016 Published: August 04, 2022

This paper is behind a paywall.