Two new kinds of on-skin electronics allow users to build and customize them directly on the body – with potential applications in biometric sensing, medical monitoring, interactive prosthetic makeup and more.<a href="https://www.hybridbody.human.cornell.edu/#/skinlink/">SkinLink</a>, developed by the&nbsp;<a href="https://www.hybridbody.human.cornell.edu/">Hybrid Body Lab</a> led by&nbsp;<a href="https://www.human.cornell.edu/people/hk932">Cindy Hsin-Liu Kao</a>, assistant professor of human centered design in the College of Human Ecology, is an on-skin electronic interface that can be fabricated right on the body, providing flexibility in design depending on the intended use. And&nbsp;<a href="https://www.hybridbody.human.cornell.edu/#/ecskin/">ECSkin</a> is an electrochromic display interface that also can be fabricated in situ, and features modular design through tiles that can be arranged as desired.Some of the potential applications for SkinLink include vital-sign and posture monitoring, proximity sensing and body art.“Both of these projects are modular prototyping toolkits, to enable much more intricate on-skin circuitry prototyping,” Kao said. “And users are able to build the circuitry directly on the skin surface.”Doctoral student and lab member Pin-Sung Ku is lead author of “<a href="https://dl.acm.org/doi/10.1145/3596241">SkinLink:&nbsp;On-body Construction and Prototyping of Reconfigurable Epidermal Interfaces</a>,” which was presented in early October at UbiComp/ISWC ’24, the Association for Computing Machinery’s international joint conference on pervasive and ubiquitous computing.The work earned a Distinguished Paper Award from the journal, Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, where it was originally published in June 2023.<a href="https://dl.acm.org/doi/10.1145/3659613">ECSkin: Tessellating Electrochromic Films for Reconfigurable On-skin Displays</a>, which published May 15, 2024, in the same journal and for which Ku is also lead author, was also presented at the conference. Kao is senior author for both papers.SkinLink represents a step forward from&nbsp;<a href="https://news.cornell.edu/stories/2022/11/skinkit-offers-versatile-wearable-skin-computing">SkinKit, which the lab developed</a> and presented at UbiComp in 2021. The earlier iteration featured slim and flexible printed circuit boards in temporary tattoo form, but the boards had predefined behaviors and larger surface areas, making customizability a challenge.“There were several issues we didn’t address in SkinKit, such as how to allow users to program the modules the way they want to,” Ku said. “For SkinKit, everything was pre-programmed; users had to attach things in a certain order. With SkinLink, there is more customizability of the functions they like.”With SkinKit, for example, the circuitry had to be built before applying it to the body; with SkinLink, users can put one module on the body, then another, for more customizability.&nbsp;The SkinLink toolkit consists of functional circuit modules, made of flexible printed circuit boards, and flexible, custom-designed wiring (called trace modules, or traces) that connect the sensor and actuator modules to the microcontroller board.That’s a key difference from SkinKit: Smaller circuit boards are connect via flexible wiring, allowing for greater freedom of motion without sacrificing connectivity.&nbsp; “The circuit boards are somewhat rigid,” Ku said, “but we created the traces to be elastic, stretchable and flexible, so as not to hinder body movement.”The on-body fabrication process starts with selecting and programming the circuit board and trace modules. The microcontroller board can be repeatedly programmed during this step, to fine-tune the circuit functions. The boards can be temporarily placed on the body and customized, before final placement.The researchers conducted A/B testing of SkinLink, comparing its usability with SkinKit in a 14-person study, and found that SkinLink enables a more flexible wiring process than SkinKit, along with unrestricted circuit arrangement and superior wearability. Compared to the SkinKit, the SkinLink interface has a much smaller footprint, better stretchability, easier fabricating and more seamless wear.SkinKit, Kao said, offered a “low floor” – a term coined by computer scientist Ben Shneiderman, meaning that people with little or no experience can quickly get started designing and prototyping wearable tech. SkinLink takes it a couple of steps further, she said.“Another goal is what we call ‘high ceilings and wide walls,’” she said. “High ceilings means increasing the complexity of the prototypes; wide walls refers to the vast array of things that could be designed. That’s what I think SkinLink really does.”Kao said she sees both SkinLink and ECSkin as “enabling technologies,” with a variety of potential uses. Some of the studies with SkinLink involved artists, wearable tech researchers, and psychology researchers for physiology sensing; she also envisions applications beyond humans.&nbsp;“Being able to use this as a functional technology for physiological sensing or artistic practice is one application,” she said. “Our work has focused on skin interfaces for humans, but I think there could also be potential for designing ‘skin’ interfaces for other living beings, such as animals, and sensing for agricultural purposes, even on plants. We are interested in bringing SkinLink to broader disciplines to support on-skin prototyping.”

An ECSkin on-body display, composed of modular electrochromic films, is flexible and soft, and easily conforms to complex body parts such as the wrist. Hybrid Body Lab/Provided

Two new kinds of on-skin electronics allow users to build and customize them directly on the body – with potential applications in biometric sensing, medical monitoring, interactive prosthetic makeup and more.

On-body electronics can monitor health, support creative expression

In this episode, we explore an innovative prosthesis driven by the nervous system that helps people with amputations walk naturally and discover how this cutting-edge technology is transforming mobility and enhancing the quality of life for amputees by restoring a natural gait.

Podcast: Bionics Help Amputees Take Big Strides Forward

This article was discussed in our <a href="https://www.wevolver.com/profile/the.next.byte" 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/ceb16e69-0075-4e23-97b8-f679ee5b172e?dark=false" class="fr-draggable" data-gtm-yt-inspected-24="true" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"></iframe> The full article will continue below.<hr>State-of-the-art prosthetic limbs can help people with amputations achieve a natural walking gait, but they don’t give the user full neural control over the limb. Instead, they rely on robotic sensors and controllers that move the limb using predefined gait algorithms.Using a new type of surgical intervention and neuroprosthetic interface, MIT researchers, in collaboration with colleagues from Brigham and Women’s Hospital, have shown that a natural walking gait is achievable using a prosthetic leg fully driven by the body’s own nervous system. The surgical amputation procedure reconnects muscles in the residual limb, which allows patients to receive “proprioceptive” feedback about where their prosthetic limb is in space.In a study of seven patients who had this surgery, the MIT team found that they were able to walk faster, avoid obstacles, and climb stairs much more naturally than people with a traditional amputation.<iframe width="640" height="360" src="https://www.youtube.com/embed/fKdnu50Nx-8?&amp;wmode=opaque&amp;rel=0&amp;enablejsapi=1&amp;origin=https://www.wevolver.com" frameborder="0" allowfullscreen="" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true" data-gtm-yt-inspected-24="true" id="651131305" title="Helping people with amputation walk naturally">&nbsp;</iframe>“This is the first prosthetic study in history that shows a leg prosthesis under full neural modulation, where a biomimetic gait emerges.&nbsp;No one has been able to show this level of brain control that produces a natural gait, where the human’s nervous system is controlling the movement, not a robotic control algorithm,” says Hugh Herr,&nbsp;a professor of media arts and sciences, co-director of the K. Lisa Yang Center for Bionics at MIT, an associate member of MIT’s McGovern Institute for Brain Research, and the senior author of the new study.Patients also experienced less pain and less muscle atrophy following this surgery, which is known as the agonist-antagonist myoneural interface (AMI). So far, about 60 patients around the world have received this type of surgery, which can also be done for people with arm amputations.Hyungeun Song, a postdoc in MIT’s Media Lab, is the lead author of the <a href="https://www.nature.com/articles/s41591-024-02994-9" target="_blank">paper</a>, which appears today in Nature Medicine.<h2>Sensory feedback</h2>Most limb movement is controlled by pairs of muscles that take turns stretching and contracting. During a traditional below-the-knee amputation, the interactions of these paired muscles are disrupted. This makes it very difficult for the nervous system to sense the position of a muscle and how fast it’s contracting — sensory information that is critical for the brain to decide how to move the limb.People with this kind of amputation may have trouble controlling their prosthetic limb because they can’t accurately sense where the limb is in space. Instead, they rely on robotic controllers built into the prosthetic limb. These limbs also include sensors that can detect and adjust to slopes and obstacles.To try to help people achieve a natural gait under full nervous system control, Herr and his colleagues began developing the AMI surgery several years ago. Instead of severing natural agonist-antagonist muscle interactions, they connect the two ends of the muscles so that they still dynamically communicate with each other within the residual limb. This surgery can be done during a primary amputation, or the muscles can be reconnected after the initial amputation as part of a revision procedure.“With the AMI amputation procedure, to the greatest extent possible, we attempt to connect native agonists to native antagonists in a physiological way so that after amputation, a person can move their full phantom limb with physiologic levels of proprioception and range of movement,” Herr says.In a 2021 <a href="https://news.mit.edu/2021/surgery-control-prosthetic-limbs-0215" target="_blank">study</a>, Herr’s lab found that patients who had this surgery were able to more precisely control the muscles of their amputated limb, and that those muscles produced electrical signals similar to those from their intact limb.After those encouraging results, the researchers set out to explore whether those electrical signals could generate commands for a prosthetic limb and at the same time give the user feedback about the limb’s position in space. The person wearing the prosthetic limb could then use that proprioceptive feedback to volitionally adjust their gait as needed.In the new Nature Medicine study, the MIT team found this sensory feedback did indeed translate into a smooth, near-natural ability to walk and navigate obstacles.“Because of the AMI neuroprosthetic interface, we were able to boost that neural signaling, preserving as much as we could. This was able to restore a person's neural capability to continuously and directly control the full gait, across different walking speeds, stairs, slopes, even going over obstacles,” Song says.<h2>A natural gait</h2>For this study, the researchers compared seven people who had the AMI surgery with seven who had traditional below-the-knee amputations. All of the subjects used the same type of bionic limb: a prosthesis with a powered ankle as well as electrodes that can sense electromyography (EMG) signals from the tibialis anterior the gastrocnemius muscles. These signals are fed into a robotic controller that helps the prosthesis calculate how much to bend the ankle, how much torque to apply, or how much power to deliver.The researchers tested the subjects in several different situations: level-ground walking across a 10-meter pathway, walking up a slope, walking down a ramp, walking up and down stairs, and walking on a level surface while avoiding obstacles.In all of these tasks, the people with the AMI neuroprosthetic interface were able to walk faster — at about the same rate as people without amputations — and navigate around obstacles more easily. They also showed more natural movements, such as pointing the toes of the prosthesis upward while going up stairs or stepping over an obstacle, and they were better able to coordinate the movements of their prosthetic limb and their intact limb. They were also able to push off the ground with the same amount of force as someone without an amputation.“With the AMI cohort, we saw natural biomimetic behaviors emerge,” Herr says.&nbsp;“The cohort that didn’t have the AMI, they were able to walk, but the prosthetic movements weren’t natural, and their movements were generally slower.”These natural behaviors emerged even though the amount of sensory feedback provided by the AMI was less than 20 percent of what would normally be received in people without an amputation.“One of the main findings here is that a small increase in neural feedback from your amputated limb can restore significant bionic neural controllability, to a point where you allow people to directly neurally control the speed of walking, adapt to different terrain, and avoid obstacles,” Song says.“This work represents yet another step in us demonstrating what is possible in terms of restoring function in patients who suffer from severe limb injury. It is through collaborative efforts such as this that we are able to make transformational progress in patient care,” says Matthew Carty, a surgeon at Brigham and Women’s Hospital and associate professor at Harvard Medical School, who is also an author of the paper.Enabling neural control by the person using the limb is a step toward Herr’s lab’s goal of “rebuilding human bodies,” rather than having people rely on ever more sophisticated robotic controllers and sensors — tools that are powerful but do not feel like part of the user’s body.“The problem with that long-term approach is that the user would never feel embodied with their prosthesis. They would never view the prosthesis as part of their body, part of self,” Herr says. “The approach we’re taking is trying to comprehensively connect the brain of the human to the electromechanics.”The research was funded by the MIT K. Lisa Yang Center for Bionics and the Eunice Kennedy Shriver National Institute of Child Health and Human Development.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzIwNDIzMTQxODg1LV9NR185NjE2LTMuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 100%px;" class="fr-fic fr-dib">Credit: Jimmy Day, MIT Media Lab

“This is the first prosthetic study in history that shows a leg prosthesis under full neural modulation,” Hugh Herr says. Image: Courtesy of Hugh Herr and Hyungeun Song

A new surgical procedure gives people more neural feedback from their residual limb. With it, seven patients walked more naturally and navigated obstacles.

A prosthesis driven by the nervous system helps people with amputation walk naturally

To advance soft robotics, skin-integrated electronics and biomedical devices, researchers at Penn State have developed a 3D-printed material that is soft and stretchable — traits needed for matching the properties of tissues and organs — and that self-assembles. Their approach employs a process that eliminates many drawbacks of previous fabrication methods, such as less conductivity or device failure, the team said. &nbsp;They published their results in <a href="https://onlinelibrary.wiley.com/doi/10.1002/adma.202400082" target="_blank">Advanced Materials</a>. &nbsp;&nbsp;“People have been developing soft and stretchable conductors for almost a decade, but the conductivity is not usually very high,” said corresponding author Tao Zhou, Penn State assistant professor of engineering science and mechanics and of biomedical engineering in the College of Engineering and of materials science and engineering in the College of Earth and Mineral Sciences. “Researchers realized they could reach high conductivity with liquid metal-based conductors, but the significant limitation of that is that it requires a secondary method to activate the material before it can reach a high conductivity.”&nbsp;Liquid metal-based stretchable conductors suffer from inherent complexity and challenges posed by the post-fabrication activation process, the researchers said. The secondary activation methods include stretching, compressing, shear friction, mechanical sintering and laser activation, all of which can lead to challenges in fabrication and can cause the liquid metal to leak, resulting in device failure. &nbsp;&nbsp;“Our method does not require any secondary activation to make the material conductive,” said Zhou, who also has affiliations with the Huck Institutes of the Life Sciences and the Materials Research Institute. “The material can self-assemble to make its bottom surface be very conductive and its top surface self-insulated.”&nbsp;In the new method, the researchers combine liquid metal, a conductive polymer mixture called PEDOT:PSS and hydrophilic polyurethane that enables the liquid metal to transform into particles. When the composite soft material is printed and heated, the liquid metal particles on its bottom surface self-assemble into a conductive pathway. The particles in the top layer are exposed to an oxygen-rich environment and oxidize, forming an insulated top layer. The conductive layer is critical for conveying information to the sensor — such as muscle activity recordings and strain sensing on the body — while the insulated layer helps prevent signal leakage that could lead to less accurate data collection.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1719495196118-240205-psnbody1-tao.jpg" style="width: 100%px;" class="fr-fic fr-dib">The new material, shown here, can self-assemble to make its bottom surface conductive and its top surface self-insulated. Credit: Marzia Momin. All Rights Reserved.“Our innovation here is a materials one,” Zhou said. “Normally, when liquid metal mixes with polymers, they are not conductive and require secondary activation to achieve conductivity. But these three components allow for the self-assembly that produces the high conductivity of soft and stretchable material without a secondary activation method.” &nbsp;The material can also be 3D-printed, Zhou said, making it easier to fabricate wearable devices. The researchers are continuing to explore potential applications, with a focus on assistive technology for people with disabilities.&nbsp;The papers other authors are Salahuddin Ahmed, Marzia Momin and Jiashu Ren, all doctoral students in the Penn State engineering science and mechanics department, and Hyunjin Lee, a doctoral student in the biomedical engineering department at Penn State. This work was supported by the National Taipei University of Technology-Penn State Collaborative Seed Grant Program and by the Department of Engineering Science and Mechanics, the Materials Research Institute and the Huck Institutes of the Life Sciences at Penn State.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1719495222063-240205-psnbody2-tao.jpg" style="width: 100%px;" class="fr-fic fr-dib">The researchers 3D print the novel material.&nbsp;Credit: Marzia Momin. All Rights Reserved.

Penn State researchers developed a new soft and stretchable material that can be 3D-printed. The material can be used to fabricate wearable devices, such a sensor that can be worn on a finger, as shown here. Credit: Marzia Momin. All Rights Reserved.

To advance soft robotics, skin-integrated electronics and biomedical devices, researchers at Penn State have developed a 3D-printed material that is soft and stretchable — traits needed for matching the properties of tissues and organs — and that self-assembles.

Self-assembling, highly conductive sensors could improve wearable devices

In this episode, we discuss a breakthrough from ETH Zurich to mimic natural foot signals to the brain using state of the art neuroprosthetics. 

Podcast: Neuroprosthetics: The Next Step Towards Limb Reconstruction

In this episode, we discuss how CalTech researchers have created bionic jellyfish to help us explore the oceans and better understand the impacts of climate change.

Podcast: Jellyfish Cyborgs Help Explore The Oceans & Solve Climate Change

The digital revolution has undeniably transformed how we access information and complete tasks, with laptops, tablets, and smartphones becoming ubiquitous companions in both our personal and professional lives. While these devices offer undeniable benefits, their constant use can also pose new challenges to our well-being, raising concerns about potential impacts on visual health and musculoskeletal function.One emerging area of concern is the intersection of presbyopia, a natural age-related decline in near vision, and the use of progressive lenses. These lenses, often referred to as 'no-line bifocals', &nbsp;provide wearers with a seamless transition between near and far vision, addressing the challenges of presbyopia. However, research suggests that the way we use progressive lenses, with their specific viewing zones, may subtly alter our head and neck postures, potentially leading to discomfort or even musculoskeletal disorders.To shed light on this issue, FREMAP, a leading Spanish mutual benefit association, embarked on a <a href="https://practicapreventiva.fremap.es/2023/02/09/uso-de-dispositivos-digitales-con-gafas-progresivas/" target="_blank" rel="noopener noreferrer">research</a> study to objectively assess the impact of progressive lenses on workplace ergonomics. Their primary objective was to quantify the visual and postural changes associated with using these lenses in a typical workstation environment. <img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzEwODM2NzM4NDQxLWVtaWFwLTEuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 100%px;" class="fr-fic fr-dib">Worker wearing progressive lenses with the Xsens motion capture sensors to analyze postural changesTo achieve this objective, the research team, led by National Ergonomics Consultant at FREMAP Prevention, D. Antonio Emir Díaz Martínez, employed <a href="https://www.movella.com/products/motion-capture" target="_blank" rel="noopener noreferrer">Xsens Motion Capture technolog</a>y, specifically an upper body configuration with 11 strategically placed inertial sensors. This system was integrated with FREMAP's own ergonomics recording, analysis and representation software, utilizing <a href="https://www.movella.com/products/motion-capture/mvn-analyze" target="_blank" rel="noopener noreferrer">Xsens Analyze Pro</a> for data processing. This setup allowed for the accurate capture and analysis of human movement and posture data.Antonio Emir Díaz Martínez, commented: "The use of this system allows us to quantify, concisely, precisely, and without interference with normal working conditions, the postural requirements of the cervical spine in workplaces with screens for data visualization. This is thanks to having a software solution that removes the possible interferences caused by local magnetic fields."By leveraging Xsens Motion Capture, the FREMAP researchers were able to quantify the precise head and neck movements associated with using progressive lenses while interacting with a computer screen.The research involved monitoring the grazing and cervical spine movements of a worker wearing progressive glasses while they interacted with a computer workstation. To ensure standardized conditions, the upper part of the screen was positioned at eye level, maintaining a distance of 60 cm from the worker. Additionally, the worker's posture was controlled by having them maintain their back against the chair's backrest and their elbows bent at an angle of approximately 80 degrees.Research Findings and RecommendationsThe analysis revealed that participants maintained consistent neck extension throughout the study, exceeding recommended ergonomic limits. This posture is likely linked to the need to look through the lower portion of progressive lenses for optimal near vision. While neck turning remained within acceptable limits, occasional lateral tilts suggest further ergonomic adjustments may be necessary.Based on the findings, the research makes the following recommendations for progressive lens users.<ul><li>Screen Positioning:&nbsp;Ensure the screen is positioned correctly for optimal viewing. Adjust the viewing distance based on task and screen size (400-750 mm for common office monitors). Consider increasing font size for individuals with progressive lenses to increase viewing distance and minimize reliance on the lower lens segment.</li><li>Screen Height: For progressive lens users, reduce the screen height significantly compared to the standard recommendation of aligning the top of the screen with eye level. This helps avoid neck extension for viewing through the lower lens zone.</li><li>Document Holders: Utilize adjustable lecterns or document holders to facilitate switching between digital and printed materials, minimizing strain on eye accommodation.</li><li>Recovery Breaks:&nbsp;Encourage frequent breaks to rest the eyes and change posture, especially for those wearing progressive lenses.</li><li>Occupational Spectacles: For individuals with presbyopia and prolonged digital device use, consider occupational spectacles specifically designed for computer work.</li><li>Training and Awareness:&nbsp;Educate first-time progressive lens users about adaptation exercises and the importance of adjusting their workstation layout. Encourage them to adopt healthy postural habits and avoid extended periods of static posture at their workstation.</li></ul>By implementing these recommendations, individuals who rely on progressive lenses can create a more ergonomically friendly workspace and potentially mitigate the risks associated with prolonged computer use.This research project by FREMAP provides valuable insights into the potential impact of progressive lenses on workplace ergonomics. By utilizing advanced motion capture technology like Xsens, the study offers a quantifiable and objective perspective on this complex issue. The findings can help inform future research, guide the development of ergonomic interventions, and ultimately contribute to promoting healthy workplace practices for individuals reliant on progressive lenses.Xsens motion capture for ergonomics assessments<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzEwODM3MDc2NDU2LWVtaWFwLTIuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 100%px;" class="fr-fic fr-dib">Accurate motion data: Xsens Awinda Motion Capture Technology featuring 18 inertial sensorsEnsuring proper workplace ergonomics is crucial for employee well-being, regulatory compliance, and increased productivity. This focus stems from the significant prevalence of musculoskeletal disorders (MSDs), often linked to poor ergonomics, affecting nearly 1.71 billion people globally.However, traditional assessment methods can be time-consuming and rely on subjective observations, potentially hindering accurate risk identification. Xsens Motion capture technology offers a compelling solution. Xsens captures objective and validated data on worker movements, eliminating subjectivity and increasing data collection efficiency. This empowers companies to swiftly identify potential hazards and make informed decisions regarding workplace design and modifications. Ultimately, this fosters safer and more productive workspaces, leading to a thriving and healthy working environment for all.<a href="https://www.movella.com/applications/health-sports/workplace-ergonomics" target="_blank" rel="noopener noreferrer">Learn more</a> about Xsens solutions for workplace ergonomics.&nbsp;

FREMAP uses Xsens motion capture to analyze the ergonomic impact of progressive lenses in the workplace and makes recommendations for improvement

Ergonomic impact of progressive lenses in the workplace

In this episode, we discuss a novel sticker capable of monitoring the health of organs in real time allowing for more successful organ transplants and catching signs of diseases earlier than ever!

Podcast: Sticker to Monitor Your Internal Organs

This article was discussed in our <a href="https://www.wevolver.com/profile/the.next.byte" 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/b5ad041a-a5dc-42cd-900b-390dca184186?dark=false" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"></iframe> The full article will continue below.<hr>A few years ago, a team of researchers working under Professor Stanisa Raspopovic at the ETH Zurich Neuroengineering Lab gained worldwide attention when they announced that their prosthetic legs had enabled amputees to feel sensations from this artificial body part for the first time. Unlike commercial leg prostheses, which simply provide amputees with stability and support, the ETH researchers’ prosthetic device was connected to the sciatic nerve in the test subjects’ thigh via implanted electrodes.This electrical connection enabled the neuroprosthesis to communicate with the patient’s brain, for example relaying information on the constant changes in pressure detected on the sole of the prosthetic foot when walking. This gave the test subjects greater confidence in their prosthesis – and it enabled them to walk considerably faster on challenging terrains. “Our experimental leg prosthesis succeeded in evoking natural sensations. That’s something current neuroprostheses are mainly unable to do; instead, they mostly evoke artificial, unpleasant sensations,” Raspopovic says.This is probably because today’s neuroprosthetics are using time-constant electrical pulses to stimulate the nervous system. “That’s not only unnatural, but also inefficient,” Raspopovic says. In a recently published paper, he and his team used the example of their leg prostheses to highlight the benefits of using naturally inspired, biomimetic stimulation to develop the next generation of neuroprosthetics.<h2>Model simulates activation of nerves in the sole</h2>To generate these biomimetic signals, Natalija Katic – a doctoral student in Raspopovic’s research group – developed a computer model called FootSim. It is based on data collected by collaborators in Canada, who recorded the activity of natural receptors, named mechanoreceptors, in the sole of the foot while touching different points on the feet of volunteers with a vibrating rod.The model simulates the dynamic behaviour of large numbers of mechanoreceptors in the sole of the foot and generates the neural signals that shoot up the nerves in the leg towards the brain – from the moment the heel strikes the ground and the weight of the body starts to shift forward to the outside of the foot until the toes push off the ground ready for the next step. “Thanks to this model, we can see how semsory receptors from the sole, and the connected nerves, behave during walking or running, which is experimentally impossible to measure” Katic says.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA5ODI0NDc4NjY1LWltYWdlLmltYWdlZm9ybWF0LjEyODYuNDg4NzEzNzM4LmpwZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 100%px;" class="fr-fic fr-dib">Restoring natural sensory feedback results in functional and cognitive benefits for leg prosthesis users. (Photograph: Pietro Comaschi)Restoring natural sensory feedback results in functional and cognitive benefits for leg prosthesis users.&nbsp;(Photograph: Pietro Comaschi)<h2 id="isPasted">Information overload in the spinal cord</h2>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;To assess how closely the biomimetic signals calculated by the model correspond to the signals emitted by real neurons, Giacomo Valle – a postdoc in Raspopovic’s research group – worked with colleagues in Germany, Serbia and Russia on experiments with cats, whose nervous system processes movement in a similar way to that of humans. The experiments took place in 2019 at the Pavlov Institute of Physiology in St. Petersburg and were carried out in accordance with the relevant European Union guidelines.The researchers implanted electrodes, connecting some to the nerve in the leg and some to the spinal cord to discover how the signals are transmitted through the nervous system. When the researchers applied pressure to the bottom of the cat’s paw, thereby evoking the natural neural response that occurs when a cat takes a step, the peculiar pattern of activity recorded in the spinal cord did indeed resemble the patterns that were elicited in the spinal cord when the researchers stimulated the leg nerve with biomimetic signals.By contrast, the conventional approach of time-constant stimulation of the sciatic nerve in the cat’s thigh elicited a markedly different pattern of activation in the spinal cord. “This clearly shows that the commonly used stimulation methods cause the neural networks in the spine to be flooded with information,” Valle says. “This information overload could be the reason for the unpleasant sensations or paraesthesia reported by some users of neuroprosthetics,” Raspopovic adds.<h2>Learning the language of the nervous system</h2>In their clinical trial with leg amputees, the researchers were able to show that biomimetic stimulation is superior to time-constant stimulation. Their work clearly demonstrated how the signals that mimicked nature produced better results: not only were the test subjects able to climb steps faster, they also made fewer mistakes in a task that required them to climb the same steps while spelling words backwards. “Biomimetic neurostimulation allows subjects to concentrate on other things while walking,” Raspopovic says, “so we concluded that this type of stimulation is more naturally processed and less taxing on the brain.”Raspopovic, whose lab forms part of the ETH Institute of Robotics and Intelligent Systems, believes that these new findings are not only relevant to the limb prostheses he and his team have been working on for over half a decade. He argues that the need to move away from unnatural, time-constant stimulation towards biomimetic signals also applies to a whole series of other aids and devices, including spinal implants and electrodes for brain stimulation. “We need to learn the language of the nervous system,” Raspopovic says. “Then we’ll be able to communicate with the brain in ways it really understands.”<h2>Information overload in the spinal cord</h2>To assess how closely the biomimetic signals calculated by the model correspond to the signals emitted by real neurons, Giacomo Valle – a postdoc in Raspopovic’s research group – worked with colleagues in Germany, Serbia and Russia on experiments with cats, whose nervous system processes movement in a similar way to that of humans. The experiments took place in 2019 at the Pavlov Institute of Physiology in St. Petersburg and were carried out in accordance with the relevant European Union guidelines.The researchers implanted electrodes, connecting some to the nerve in the leg and some to the spinal cord to discover how the signals are transmitted through the nervous system. When the researchers applied pressure to the bottom of the cat’s paw, thereby evoking the natural neural response that occurs when a cat takes a step, the peculiar pattern of activity recorded in the spinal cord did indeed resemble the patterns that were elicited in the spinal cord when the researchers stimulated the leg nerve with biomimetic signals.By contrast, the conventional approach of time-constant stimulation of the sciatic nerve in the cat’s thigh elicited a markedly different pattern of activation in the spinal cord. “This clearly shows that the commonly used stimulation methods cause the neural networks in the spine to be flooded with information,” Valle says. “This information overload could be the reason for the unpleasant sensations or paraesthesia reported by some users of neuroprosthetics,” Raspopovic adds.<h2>Learning the language of the nervous system</h2>In their clinical trial with leg amputees, the researchers were able to show that biomimetic stimulation is superior to time-constant stimulation. Their work clearly demonstrated how the signals that mimicked nature produced better results: not only were the test subjects able to climb steps faster, they also made fewer mistakes in a task that required them to climb the same steps while spelling words backwards. “Biomimetic neurostimulation allows subjects to concentrate on other things while walking,” Raspopovic says, “so we concluded that this type of stimulation is more naturally processed and less taxing on the brain.”Raspopovic, whose lab forms part of the ETH Institute of Robotics and Intelligent Systems, believes that these new findings are not only relevant to the limb prostheses he and his team have been working on for over half a decade. He argues that the need to move away from unnatural, time-constant stimulation towards biomimetic signals also applies to a whole series of other aids and devices, including spinal implants and electrodes for brain stimulation. “We need to learn the language of the nervous system,” Raspopovic says. “Then we’ll be able to communicate with the brain in ways it really understands.”<hr><h2 id="isPasted">Reference</h2>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;Valle G, Katic Secerovic N, Eggemann D, Gorskii O, Pavlova N, Petrini FM, Cvancara P, Stieglitz T, Musienko P, Bumbasirevic M, Raspopovic S: Biomimetic computer-to-brain communication enhancing naturalistic touch sensations via peripheral nerve stimulation. Nature Communications, 20 February 2024, doi: <a href="https://doi.org/10.1038/s41467-024-45190-6" target="_blank">external page10.1038/s41467-024-45190-6</a>

ETH researchers have developed a prosthetic leg that communicates with the brain via natural signals. (Photograph: Keystone)

Prostheses that connect to the nervous system have been available for several years. Now, researchers at ETH Zurich have found evidence that neuroprosthetics work better when they use signals that are inspired by nature.

Bio-inspired neuroprosthetics: sending signals the brain can understand

This article was discussed in our <a href="https://www.wevolver.com/profile/the.next.byte" 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/18c9c9fd-d774-46bc-87b8-fb1b0e7a5ae4?dark=false" class="fr-draggable" data-gtm-yt-inspected-9="true" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"></iframe> The full article will continue below.<hr>Jellyfish can't do much besides swim, sting, eat, and breed. They don't even have brains. Yet, these simple creatures can easily journey to the depths of the oceans in a way that humans, despite all our sophistication, cannot.But what if humans could have jellyfish explore the oceans on our behalf, reporting back what they find? New research conducted at Caltech aims to make that a reality through the creation of what researchers call biohybrid robotic jellyfish. These creatures, which can be thought of as ocean-going cyborgs, augment jellyfish with electronics that enhance their swimming and a prosthetic "hat" that can carry a small payload while also making the jellyfish swim in a more streamlined manner.The work, published in the journal Bioinspiration &amp; Biomimetics, was conducted in the lab of John Dabiri (MS '03, PhD '05), the Centennial Professor of Aeronautics and Mechanical Engineering, and builds on his previous work augmenting jellyfish. Dabiri's goal with this research is to use jellyfish as robotic data-gatherers, sending them into the oceans to collect information about temperature, salinity, and oxygen levels, all of which are affected by Earth's changing climate."It's well known that the ocean is critical for determining our present and future climate on land, and yet, we still know surprisingly little about the ocean, especially away from the surface," Dabiri says. "Our goal is to finally move that needle by taking an unconventional approach inspired by one of the few animals that already successfully explores the entire ocean."<iframe width="640" height="360" src="https://www.youtube.com/embed/_ZfthP_7s5g?&amp;wmode=opaque&amp;rel=0&amp;enablejsapi=1&amp;origin=https://www.wevolver.com" frameborder="0" allowfullscreen="" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true" data-gtm-yt-inspected-9="true" id="779481107" title="Robotic Jellyfish Explorers">&nbsp;</iframe>Media assets: Robotic Jellyfish ExplorersThroughout his career, Dabiri has looked to the natural world, jellyfish included, for inspiration in solving engineering challenges. This work began with early attempts by Dabiri's lab to develop a mechanical robot that swam like jellyfish, which have the most efficient method for traveling through water of any living creature. Though his research team succeeded in creating such a robot, that robot was never able to swim as efficiently as a real jellyfish. At that point, Dabiri asked himself, why not just work with jellyfish themselves?"Jellyfish are the original ocean explorers, reaching its deepest corners and thriving just as well in tropical or polar waters," Dabiri says. "Since they don't have a brain or the ability to sense pain, we've been able to collaborate with bioethicists to develop this biohybrid robotic application in a way that's ethically principled."Previously, Dabiri's lab implanted jellyfish with a kind of electronic pacemaker that controls the speed at which they swim. In doing so, they found that if they made jellyfish swim faster than the leisurely pace they normally keep, the animals became even more efficient. A jellyfish swimming three times faster than it normally would uses only twice as much energy.This time, the research team went a step further, adding what they call a forebody to the jellies. These forebodies are like hats that sit atop the jellyfish's bell (the mushroom-shaped part of the animal). The devices were designed by graduate student and lead author Simon Anuszczyk (MS '22), who aimed to make the jellyfish more streamlined while also providing a place where sensors and other electronics can be carried."Much like the pointed end of an arrow, we designed 3D-printed forebodies to streamline the bell of the jellyfish robot, reduce drag, and increase swimming performance," Anuszczyk says. "At the same time, we experimented with 3D printing until we were able to carefully balance the buoyancy and keep the jellyfish swimming vertically."To test the augmented jellies' swimming abilities, Dabiri's lab undertook the construction of a massive vertical aquarium inside Caltech's Guggenheim Laboratory. Dabiri explains that the three-story tank is tall, rather than wide, because researchers want to gather data on oceanic conditions far below the surface."In the ocean, the round trip from the surface down to several thousand meters will take a few days for the jellyfish, so we wanted to develop a facility to study that process in the lab," Dabiri says. "Our vertical tank lets the animals swim against a flowing vertical current, like a treadmill for swimmers. We expect the unique scale of the facility—probably the first vertical water treadmill of its kind—to be useful for a variety of other basic and applied research questions."<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA5NTIxNzc5NzI4LURhYmlyaS1MYWItTG9uZy1EaXN0YW5jZS1Td2ltbWluZ19Gb3JlYm9keTMubWF4LTE0MDB4ODAwLmpwZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 100%px;" class="fr-fic fr-dib">A biohybrid jellyfish descends through the three-story tank in which swimming tests were conducted. Credit: CaltechSwim tests conducted in the tank show that a jellyfish equipped with a combination of the swimming pacemaker and forebody can swim up to 4.5 times faster than an all-natural jelly while carrying a payload. The total cost is about $20 per jellyfish, Dabiri says, which makes biohybrid jellies an attractive alternative to renting a research vessel that can cost more than $50,000 a day to run."By using the jellyfish's natural capacity to withstand extreme pressures in the deep ocean and their ability to power themselves by feeding, our engineering challenge is a lot more manageable," Dabiri adds. "We still need to design the sensor package to withstand the same crushing pressures, but that device is smaller than a softball, making it much easier to design than a full submarine vehicle operating at those depths."I'm really excited to see what we can learn by simply observing these parts of the ocean for the very first time," he adds.Dabiri says future work may focus on further enhancing the bionic jellies' abilities. Right now, they can only be made to swim faster in a straight line, such as the vertical paths being designed for deep ocean measurement. But further research may also make them steerable, so they can be directed horizontally as well as vertically.The paper describing the work, "<a href="https://iopscience.iop.org/article/10.1088/1748-3190/ad277f" target="_blank">Electromechanical enhancement of live jellyfish for ocean exploration</a>," appears in the February 28 issue of Bioinspiration &amp; Biomimetics. Co-authors are Anuszczyk and Dabiri.

Jellyfish can't do much besides swim, sting, eat, and breed. They don't even have brains. Yet, these simple creatures can easily journey to the depths of the oceans in a way that humans, despite all our sophistication, cannot.

Building Bionic Jellyfish for Ocean Exploration

In this episode, we discuss the shortcomings of previous attempts at making flexible wearable sensors and how researchers at CalTech have addressed them to create high performance stress sensor stickers.

Stress Sensing Stickers

This article was discussed in our <a href="https://www.wevolver.com/profile/the.next.byte" 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/1e9bb08c-384a-4d12-983e-8af2e63c741b?dark=false" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"></iframe> The full article will continue below.<hr>MIT engineers have developed a small ultrasound sticker that can monitor the stiffness of organs deep inside the body. The sticker, about the size of a postage stamp, can be worn on the skin and is designed to pick up on signs of disease, such as liver and kidney failure and the progression of solid tumors.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA3NzI0MzU5MjkzLU1JVC1TZWVpbmdTdGlmZm5lc3MtMDEtcHJlc3NfMC5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 766px;" class="fr-fic fr-dib">A small ultrasound sticker, worn on the skin, can monitor the stiffness of organs deep inside the body. The MIT-developed sensor could detect signs of disease such as liver and kidney failure, and the progression of solid tumors. Image: Courtesy of the researchersIn an <a href="https://science.org/doi/10.1126/sciadv.adk8426" target="_blank">open-access study appearing today</a> in Science Advances, the team reports that the sensor can send sound waves through the skin and into the body, where the waves reflect off internal organs and back out to the sticker. The pattern of the reflected waves can be read as a signature of organ rigidity, which the sticker can measure and track.“When some organs undergo disease, they can stiffen over time,” says the senior author of the paper, Xuanhe Zhao, professor of mechanical engineering at MIT. “With this wearable sticker, we can continuously monitor changes in rigidity over long periods of time, which is crucially important for early diagnosis of internal organ failure.”The team has demonstrated that the sticker can continuously monitor the stiffness of organs over 48 hours and detect subtle changes that could signal the progression of disease. In preliminary experiments, the researchers found that the sticky sensor can detect early signs of acute liver failure in rats.The engineers are working to adapt the design for use in humans. They envision that the sticker could be used in intensive care units (ICUs), where the low-profile sensors could continuously monitor patients who are recovering from organ transplants.“We imagine that, just after a liver or kidney transplant, we could adhere this sticker to a patient and observe how the rigidity of the organ changes over days,” lead author Hsiao-Chuan Liu says. “If there is any early diagnosis of acute liver failure, doctors can immediately take action instead of waiting until the condition becomes severe.” Liu was a visiting scientist at MIT at the time of the study and is currently an assistant professor at the University of Southern California.The study’s MIT co-authors include Xiaoyu Chen and Chonghe Wang, along with collaborators at USC.Sensing wobblesLike our muscles, the tissues and organs in our body stiffen as we age. With certain diseases, stiffening organs can become more pronounced, signaling a potentially precipitous health decline. Clinicians currently have ways to measure the stiffness of organs such as the kidneys and liver using ultrasound elastography — a technique similar to ultrasound imaging, in which a technician manipulates a handheld probe or wand over the skin. The probe sends sound waves through the body, which cause internal organs to vibrate slightly and send waves out in return. The probe senses an organ’s induced vibrations, and the pattern of the vibrations can be translated into how wobbly or stiff the organ must be.Ultrasound elastography is typically used in the ICU to monitor patients who have recently undergone an organ transplant. Technicians periodically check in on a patient shortly after surgery to quickly probe the new organ and look for signs of stiffening and potential acute failure or rejection.“After organ transplantation, the first 72 hours is most crucial in the ICU,” says another senior author, Qifa Zhou, a professor at USC. “With traditional ultrasound, you need to hold a probe to the body. But you can’t do this continuously over the long term. Doctors might miss a crucial moment and realize too late that the organ is failing.”The team realized that they might be able to provide a more continuous, wearable alternative. Their solution expands on an <a href="https://news.mit.edu/2022/ultrasound-stickers-0728" target="_blank">ultrasound sticker</a> they previously developed to image deep tissues and organs.“Our imaging sticker picked up on longitudinal waves, whereas this time we wanted to pick up shear waves, which will tell you the rigidity of the organ,” Zhao explains.Existing ultrasound elastrography probes measure shear waves, or an organ’s vibration in response to sonic impulses. The faster a shear wave travels in the organ, the stiffer the organ is interpreted to be. (Think of the bounce-back of a water balloon compared to a soccer ball.)The team looked to miniaturize ultrasound elastography to fit on a stamp-sized sticker. They also aimed to retain the same sensitivity of commercial hand-held probes, which typically incorporate about 128 piezoelectric transducers, each of which transforms an incoming electric field into outgoing sound waves.“We used advanced fabrication techniques to cut small transducers from high-quality piezoelectric materials that allowed us to design miniaturized ultrasound stickers,” Zhou says.The researchers precisely fabricated 128 miniature transducers that they incorporated onto a 25-millimeter-square chip. They lined the chip’s underside with an adhesive made from hydrogel — a sticky and stretchy material that is a mixture of water and polymer, which allows sound waves to travel into and out of the device almost without loss.In preliminary experiments, the team tested the stiffness-sensing sticker in rats. They found that the stickers were able to take continuous measurements of liver stiffness over 48 hours. From the sticker’s collected data, the researchers observed clear and early signs of acute liver failure, which they later confirmed with tissue samples.“Once liver goes into failure, the organ will increase in rigidity by multiple times,” Liu notes.“You can go from a healthy liver as wobbly as a soft-boiled egg, to a diseased liver that is more like a hard-boiled egg,” Zhao adds. “And this sticker can pick up on those differences deep inside the body and provide an alert when organ failure occurs.”The team is working with clinicians to adapt the sticker for use in patients recovering from organ transplants in the ICU. In that scenario, they don’t anticipate much change to the sticker’s current design, as it can be stuck to a patient’s skin, and any sound waves that it sends and receives can be delivered and collected by electronics that connect to the sticker, similar to electrodes and EKG machines in a doctor’s office.“The real beauty of this system is that since it is now wearable, it would allow low-weight, conformable, and sustained monitoring over time,” says Shrike Zhang,&nbsp;an associate professor of medicine at Harvard Medical School and associate bioengineer at Brigham and Women’s Hospital, who was not involved with the study. “This would likely not only allow patients to suffer less while achieving prolonged, almost real-time monitoring of their disease progression, but also free trained hospital personnel to other important tasks.”The researchers are also hoping to work the sticker into a more portable, self-enclosed version, where all its accompanying electronics and processing is miniaturized to fit into a slightly larger patch. Then, they envision that the sticker could be worn by patients at home, to continuously monitor conditions over longer periods, such as the progression of solid tumors, which are known to harden with severity.“We believe this is a life-saving technology platform,” Zhao says. “In the future, we think that people can adhere a few stickers to their body to measure many vital signals, and image and track the health of major organs in the body.”

“We used advanced fabrication techniques to cut small transducers from high-quality piezoelectric materials that allowed us to design miniaturized ultrasound stickers,” Xuanhe Zhao, professor of mechanical engineering at MIT, says. Image: Courtesy of the researchers

The sticky, wearable sensor could help identify early signs of acute liver failure.

This ultrasound sticker senses changing stiffness of deep internal organs

The adoption of healthcare monitoring devices that are both flexible and conform to the wearer have gained traction1. Spurred on by the need for remote care during the COVID-19 pandemic and technological advances in sensor accuracy, wearable health monitoring devices have become more ubiquitous in many areas of healthcare. In particular, there has been a rise in the development of wearable sensing and monitoring devices for telemedicine operations. Telemedicine has grown significantly in the last few years—and even more so during the COVID-19 pandemic when doctor-patient contact was limited—to remotely monitor patients in their own homes so hospitals could free up much-needed beds. While wearable technologies can be used in clinical environments to provide an analysis, much of their potential is in remote health monitoring.These wearable sensing devices typically make use of flexible materials, such as polymers, thin films, 2D materials and other nanomaterials. Health monitoring devices often consist of a flexible material that conforms to the wearer and is integrated with electronic components, including sensors, a power source—be it a battery, solar cell, or some other type of energy harvester like a nanogenerator—communication technologies if it transmits data to a central processing system, and any relevant circuitry.Building electronic components that are small and flexible enough to be used in wearable technologies is not that straightforward, and is why different nanomaterials—especially 2D materials—are often used to create the components because they fit the bill and can be easily integrated. But another approach is gathering interest: printing sensors—the most crucial aspects of a monitoring system—directly onto the wearable device.These printed sensors are sometimes made of 2D materials and other nanomaterials, but other materials can also be used as well. The ability to print sensors onto wearable health monitoring devices could pave a way to a much simpler and easier route to commercializing more wearable monitoring devices—especially if conventional, inexpensive, or easy-to-use printing technologies are used to print the sensor.<h2>Why Printed Sensors?</h2>While a range of advanced deposition and nanodeposition methods exist that can fabricate thin-film sensors on the substrate for wearable devices—often a soft polymer due to their flexibility and conformability—a number of biomedical sensors can be printed using screen printing techniques. Other techniques, such as inkjet and transfer printing, can be used as well, but screen printing is seen as the best option for printing sensors.Screen printing equipment is widely available, has a relatively low cost, and is easier to use than more advanced deposition methods, so it offers a much more scalable and commercially feasible route for using printed sensors in healthcare monitoring devices. Screen printing can also be used with many materials—from polymer solutions to conductive nanomaterial inks—so it is a versatile platform for printing a number of sensors.So, why print sensors instead of creating them through other manufacturing routes? Screen printing is a simple, fast, and efficient printing technique that can produce a large number of identical patterns in a single print. For large-scale operations and commercialization potential, screen printing can easily be adapted for mass production at a lower cost than other methods.From a performance perspective, screen printing provides high-resolution patterning and can print over large areas. The ability of screen printing to deposit material on demand in a given location also helps to reduce waste—especially on large scales—compared to traditional manufacturing methods because it is all done in a single step.There are, therefore, a number of manufacturing benefits with using printing methods. Beyond that, a greater design capability exists for health wearables because printing methods enable the production of sensors that are not only very thin but also provide the ability to print on the surface of the device. This approach is much simpler than trying to integrate devices into the material matrix of the wearable. You can also create a more customized sensor because you can print on demand, and the printing process can be changed to make a different sensor much easier than a typical manufacturing line.In terms of the materials compatible with screen printing, the scope is vast. Depending on the type of sensor being created, a whole host of materials can be used. On the one hand, a range of metals can be made into printable conductive inks to build the sensor. Common metals for wearable health sensors include gold, copper, platinum, nickel, aluminum, and silver. Beyond metals, a range of nanomaterial composites (graphene, carbon nanotubes composites), functional nanomaterial inks, and silver composites have all been used as the active sensing surface in printed health wearable sensors.The sensors also need a platform to be printed on. This often takes the form of a conductive polymer so that the sensor can better interact with the skin and the other components to provide higher sensitivity and reliability. PEDOT:PSS is the polymer platform that is most widely used for printed sensors, but other polymer materials include polyacetylene, polypyrrol, polyphenylene, poly (p-phenylene vinylene), and polythiophene polyaniline.<h2>The Printed Sensors of Interest in Healthcare Monitoring Applications</h2>Just as many materials can be used to create printed health sensors, many different types of printable sensors are used in health monitoring devices. Take, for example, strain-based sensors. Strain-based sensors measure a form of movement, and these wearable sensors are used in human-physiological signal monitoring and human-joint motion monitoring approaches.Another healthcare specialty measures different biomolecules and human signals. Non-strain-based sensors detect the biomolecule of interest directly or by directly measuring a physiological parameter that the patient exhibits. From a molecule-sensing perspective, a number of biomolecules in the blood can be detected, with glucose levels being a common one as well as the presence of sweat on a person’s skin. From a signal detection perspective, printed sensors can now detect respiration and heartbeat levels in a patient and provide remote electrocardiogram (ECG) monitoring.Another class of printed sensors for wearables is sensor arrays. In sensor arrays, multiple sensors work together to detect more complex issues or issues that require analysis from several stimuli angles. Sensor arrays are helpful in monitoring gait during walking, monitoring the sitting posture of wheelchair users, and monitoring the skin.Finally, there’s been advances in the development of printed temperature sensors for wearable health devices. Thermal sensing is a key area in disease detection because the body suffers thermal stresses when there is a disease present, and the rise in both skin and deep body temperature can be a primary indicator of a serious disease. Using printed temperature sensors, health wearables can detect a range of chronic diseases, such as cardiovascular, diabetic, and pulmonological diseases, as well as cancer.<h2>Conclusion</h2>Health monitoring wearables are gaining acceptance as an effective way to remotely measure many health factors of a patient. The most important aspect of these wearables is the sensing system that provides the analysis on the patient. For patients to be willing to wear the health monitoring device over an extended amount of time, the sensors and other components need to flex with the wearable component. While integrating flexible sensors is possible—for example, by using thin nanomaterials—printing sensors on the device’s surface is much easier, requires less material, and is much more scalable.A variety of printed health wearables are already in existence (commercially and academically. The printing methods discussed offer a route to achieve widespread distribution of health wearables. While many options are available, screen printing is the leading printing technology because it is highly versatile and can be used with many materials to create sensors that monitor different aspects of a person’s health—from heart rate to detecting a chance of a disease, to the different biomolecules in their blood, and many more in between.

The COVID-19 pandemic and advancements in sensor technology have led to the widespread adoption of wearable health monitoring devices, particularly for telemedicine, to facilitate remote patient monitoring.

Printable Sensors: A Key Technology for Health Wearables?

This article was discussed in our <a href="https://www.wevolver.com/profile/the.next.byte" 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/437b67d4-99c8-455a-9ae6-e487b81825a1?dark=false" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"></iframe> The full article will continue below.<hr>In the latest of a series of innovative designs for wearable sensors that use sweat to identify and measure physiological conditions, Caltech's Wei Gao, assistant professor of medical engineering, has devised an "electronic skin" that continuously monitors nine different markers that characterize a stress response. Those wearing this electronic skin—a small, thin adhesive worn on the wrist, called CARES (consolidated artificial-intelligence-reinforced electronic skin)—are free to engage in all their normal daily activities with minimal interference during testing, which allows for the measurement of both baseline and acute levels of stress.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA2NTEyNDkyMDc2LUdhb19XZWktU3RyZXNzLVN3ZWF0LVNlbnNvci01LVdFQi53aWR0aC00NTAgKDEpLmpwZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 300px;" class="fr-fic fr-dib">Stress is a slippery concept. We talk about "feeling stressed" or a situation "being stressful," and we may attach stress to physical symptoms: "I have a stress headache" or "I'm grinding my teeth at night. It must be stress." The term stress can apply to all sorts of feelings, symptoms, behaviors, and experiences.Hans Selye, a physician and chemist born in Vienna in 1907, was the first to define stress as a medical condition. Struck by the similar complaints—such as tiredness, low appetite, and lack of motivation—that he heard from patients suffering from very different illnesses, Selye speculated that all of the patients were responding to what they had in common: being sick. He defined stress as a "nonspecific response of the body to any demand."Stress may be experienced positively as excitement or energy, or negatively as shock or anxiety. But however stress may be experienced emotionally, it is now widely agreed that depending on its severity and duration, both acute and chronic stress can damage our physical and mental health, and reduce our ability to function as we would like.Because stress is, as Selye described it, "nonspecific," there is no single biomarker available to tell us definitively whether or how much a person is stressed. However, stress generates a constellation of bodily reactions that, taken together, can provide a measure of stress independent of self-reports. Gao is monitoring this constellation with CARES.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA2NTEyNDI2MzM3LUdhb19XZWktU3RyZXNzLVN3ZWF0LVNlbnNvci00LVdFQl8zSW1tM1pKLndlYnAiLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 766px;" class="fr-fic fr-dib">A sweat sensor worn on the wrist, lifted to show the thinness of the device. Credit: Wei Gao and Changhao Xu"When a person is under stress, hormones like epinephrine, norepinephrine, and cortisol are released into the bloodstream," explains Gao, who is also an investigator with the Heritage Medical Research Institute and a Ronald and JoAnne Willens Scholar. "Sweat becomes rich with metabolites like glucose, lactate, and uric acid, and electrolytes like sodium, potassium, and ammonium. These are substances we have measured before using <a href="https://www.caltech.edu/about/news/new-wearable-sensor-detects-even-more-compounds-in-human-sweat" target="_blank">microfluidic sampling on a wearable sweat sensor</a>. What is new in CARES is that sweat sensors are integrated with sensors that record pulse waveforms, skin temperature, and galvanic skin response: physiological signals that also indicate stress in predictable ways."New materials further boost the performance of CARES. Though previously used materials for sweat sensors could be produced efficiently via inkjet printing and were capable of accurate measurement of even very scarce compounds, the materials gradually broke down in the presence of bodily fluids. The introduction of a nickel-based compound helps to stabilize the enzymatic-based sensors, such as those that detect lactate or glucose, as does a new polymer added to the ion-based sensors, which detect biomarkers like sodium or potassium. "Adding these new materials greatly enhances the sensor stability during long-term operation," Gao reports. Like previous sweat sensors, CARES can be battery powered and can wirelessly communicate with a phone or computer via Bluetooth.Another important innovation with CARES is the addition of machine learning. Because stress comes in many different forms and stimulates a complex response affecting many different bodily systems, interpreting a wealth of data accurately is key to the usefulness of CARES and other sensors. Experiments inducing stress in subjects wearing the CARES device demonstrated that the sensor accurately measures the interrelatedness of physiological (such as pulse) and chemical (such as glucose) biomarkers. Subjects also answered questionnaires to self-report their feelings of anxiety and psychological stress before and after exposure to stressful situations like vigorous exercise or intense video gameplay. Data showed clear correlations between self-reports of stress and its physicochemical correlates as measured by CARES."High levels of stress and anxiety caused by demanding work environments, such as those experienced by soldiers or astronauts, can significantly affect performance," Gao notes. "Early detection of the severity of stress allows for timely intervention. Our wearable sensor, combined with machine learning, has the potential to provide real-time stress-level insights."The paper describing the CARES device, titled "A physicochemical sensing electronic skin for stress response monitoring," appears in the January 19 issue of Nature Electronics. Co-authors are Changhao Xu (MS '20), Yu Song, Juliane R. Sempionatto, Samuel R. Solomon (MS '23), You Yu, Roland Yingjie Tay, Jiahong Li, Wenzheng Heng (MS '23), Jihong Min (MS '19), and Alison Lao of Caltech; Hnin Y. Y. Nyein of Hong Kong University of Science and Technology; and Tzung K. Hsiai and Jennifer A. Sumner of UCLA.

In the latest of a series of innovative designs for wearable sensors that use sweat to identify and measure physiological conditions, Caltech's Wei Gao has devised an "electronic skin" that continuously monitors nine different markers that characterize a stress response.

Measuring Stress

This article originally appeared in <a href="https://engineering.wustl.edu/news/2023/Brain-machine-interfaces-for-insects-to-study-principles-of-odor-guided-navigation.html" target="_blank" rel="noopener noreferrer">McKelvey School of Engineering</a> and has been republished with permission.<hr><iframe width="640" height="360" src="https://www.youtube.com/embed/dBNOGbF-e7E?&amp;wmode=opaque&amp;rel=0&amp;enablejsapi=1&amp;origin=https://www.wevolver.com" frameborder="0" allowfullscreen="" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"></iframe>The locust follows a pleasant scent on a treadmill. (Credit: Raman lab)The inviting smell of a freshly baked cookie immediately triggers a motor response to search for the source of that smell. Often the cookie can be easily found.This everyday event that we perform without a thought is an amazing feat that combines our superior ability to smell the cookie and computational prowess to determine the directions to move toward the cookie. Robots that possess similar capabilities are yet to be developed as the basic biological principles that are needed to perform this task are yet to be fully understood. &nbsp;The ability to study neural responses in behaving insects is essential to understanding the robust solutions biological systems have developed for several engineering problems. For example, locusts have survived for at least 8 million years — longer than humans have been on this planet — in nearly all parts of the earth. Their many remarkable capabilities include seeing, hearing and smelling things that humans cannot sense, jumping multiple times their body length, the uncanny ability to fly up to 100 kilometers a day, and switching between solitary and menacing swarms phases as needed for survival. They use these capabilities to find food, avoid predators, propagate their species, and do all things necessary to keep them alive. Researchers in the McKelvey School of Engineering at Washington University in St. Louis have long sought to understand the power of the locusts’ sensing, computing and locomotory capabilities.Barani Raman, professor of biomedical engineering in the McKelvey School of Engineering, is leading a multidisciplinary team to study how the locust brain transforms sensory input into behavior with a four-year, $4.3 million grant from the National Science Foundation’s Integrative Strategies for Understanding Neural and Cognitive Systems (NCS) program. The grant converges years of research in Raman’s lab with that of his longtime WashU collaborators, including Shantanu Chakrabartty, professor of electrical &amp; systems engineering, and Srikanth Singamaneni, professor of mechanical engineering &amp; materials science, as well as Alexandra Rutz, assistant professor of biomedical engineering, and Yehuda Ben-Shahar, professor of biology, also at WashU.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1697685410077-ezgif-5-9129b96817.jpg" style="width: 766px;" class="fr-fic fr-dib">Researchers in the McKelvey School of Engineering have long sought to understand the power of the locusts’ sensing, computing and locomotory capabilities. With a $4.3 million grant from the National Science Foundation, they will converge that research to develop a “cyborg,” or mobile robot or drone, that can mimic the locusts’ behaviors. (Credit: Raman lab)“Insects are an engineering marvel,” Raman said. “They possess diverse sensing modalities and locomotory responses yet contained in such a small package. We want to engineer tools to study the amazing capabilities of these relatively simpler organisms.”The research brings together Washington University’s strengths in neural engineering, integrated circuits, biomaterials, synthetic biology and genetic engineering to understand how the insects use olfactory cues to navigate toward an odor source, which could potentially be used for various applications, such as detecting gas left on in the kitchen or as the proverbial canary in the coal mine to test spaces for hazardous chemicals. In 2024, the team plans to launch the first-of-its-kind Center for Cyborg and Biorobotics Research (CyBoR) to formally conduct the research.&nbsp;The team plans to study the neural response in the locusts’ brains by having the locusts follow a specific odor on a specially built treadmill while walking on a foam ball and while flying in a wind tunnel. By studying their movements and neural activity in the brain in response to these odors, the team can process the information using a custom microchip to develop a “cyborg,” or mobile robot or drone, that can mimic the locusts’ behaviors. They also aim to augment the locusts’ ability to detect certain odors over others.“Nature already has endowed this organism with various capabilities, so why not understand and augment those capabilities using synthetic mechanisms?” asked Chakrabartty, whose expertise is in sensors and integrated circuits. “Ultimately, our goal is to design a completely synthetic system that has similar remarkable capabilities.”While the team has already joined forces to create recording instruments and nanomaterials to manipulate neural and behavioral responses, they will continue to improve on those as they develop the bio-hybrid and mobile robotic systems.&nbsp;“One of the important challenges in these studies is the limited stability of the neural recording and stimulation electrodes and interfaces over a long period,” said Singamaneni, whose expertise is in novel bio- and nanomaterials. “We aim to design and realize novel anti-inflammatory electrodes and biointerfaces that will enable stable long-term neural recording and stimulation.”Previously, <a href="https://engineering.wustl.edu/news/2016/Engineers-to-use-cyborg-insects-as-biorobotic-sensing-machines.html" target="_blank">the research team developed a miniature “backpack”</a> containing sensors that recorded the locusts’ brain activity when exposed to the odors. However, the existing backpack is too heavy for the locusts to wear while flying, so the team will work to reduce its weight.At Washington University, the research is underway in a state-of-the-art CyBoR facility that includes the habitat for the locusts, the treadmill, the wind tunnel, specialized microscopes, and space for visiting researchers as well as for visitors interested in learning about the insects. WashU students also will be included in the research as well as students from the community through various outreach programs.&nbsp;Other co-investigators include Alper Bozkurt, distinguished professor of electrical &amp; computer engineering at North Carolina State University, who will lead efforts on instrumentation for navigation control; Sawyer Fuller, assistant professor of mechanical engineering at the University of Washington, who will lead efforts to build miniaturized robots that incorporate both biological and engineering elements; and Nabil Imam, assistant professor of computational science and engineering at Georgia Tech, who will lead the development of neuromorphic algorithms and hardware in the bio-hybrid and robotic systems.

Barani Raman, professor of biomedical engineering in the McKelvey School of Engineering, is leading a multidisciplinary team to study how the locust brain transforms sensory input into behavior with a four-year, $4.3 million grant from the National Science Foundation’s Integrative Strategies for Understanding Neural and Cognitive Systems (NCS) program. 

Brain-machine interfaces for insects to study principles of odor-guided navigation

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