prosthetics and bionics

The human heart beats approximately 35 million times every year, pumping blood via four different heart valves. Unfortunately, &nbsp;in more four million people each year, these delicate tissues malfunction due to birth defects, age-related deteriorations, and infections causing cardiac valve disease.Today, clinicians use either artificial prostheses or fixed animal and cadaver-sourced tissues to replace defective valves. While these prostheses can restore the function of the heart for a while, they are associated with adverse comorbidity and wear down and need to be replaced during invasive and expensive surgeries. Moreover, in children, implanted heart valve prostheses need to be replaced even more often as they cannot grow with the child.A team lead by&nbsp;<a href="https://www.seas.harvard.edu/directory/kkparker" target="_blank">Kevin Kit Parker</a>, Tarr Family Professor of Bioengineering and Applied Physics at the<a href="http://www.seas.harvard.edu/" target="_blank">&nbsp;Harvard John A. Paulson School of Engineering and Applied Sciences&nbsp;</a>(SEAS), recently developed a nanofiber fabrication technique to rapidly manufacture heart valves with regenerative and growth potential.Parker is also a Core Faculty member of&nbsp;<a href="http://wyss.harvard.edu/" target="_blank">Wyss Institute for Biologically Inspired Engineering at Harvard University.</a>In a paper published in&nbsp;<a href="http://www.sciencedirect.com/science/article/pii/S0142961217302685" target="_blank">Biomaterials</a>, first author Andrew Capulli and colleagues fabricated a valve-shaped nanofiber network that mimics the mechanical and chemical properties of the native valve extracellular matrix (ECM). The team used the Parker lab&rsquo;s proprietary rotary jet spinning technology &ndash; in which a rotating nozzle extrudes an ECM solution into nanofibers that wrap themselves around heart valve-shaped mandrels.&ldquo;Our setup is like a very fast cotton candy machine that can spin a range of synthetic and natural occurring materials,&rdquo; said Parker. &ldquo;In this study, we used a combination of synthetic polymers and ECM proteins to fabricate biocompatible JetValves that are hemodynamically competent upon implantation and support cell migration and re-population&nbsp;in vitro. Importantly, we can make human-sized JetValves in minutes &ndash; much faster than possible for other regenerative prostheses.&rdquo;To further develop and test the clinical potential of JetValves, Parker&rsquo;s team partnered with the translational team of Simon P. Hoerstrup, at the University of Zurich. As a leader in regenerative heart prostheses, Hoerstrup and his team in Zurich previously developed regenerative, tissue-engineered heart valves to replace mechanical and fixed-tissue heart valves. In Hoerstrup&rsquo;s approach, human cells directly deposit a regenerative layer of complex ECM on biodegradable scaffolds shaped as heart valves and vessels. The living cells are then eliminated from the scaffolds resulting in an &ldquo;off-the-shelf&rdquo; human matrix-based prostheses ready for implantation.In the paper, the cross-disciplinary team successfully implanted JetValves in sheep using a minimally invasive technique and demonstrated that the valves functioned properly in the circulation and regenerated new tissue.&ldquo;In our previous studies, the cell-derived ECM-coated scaffolds could recruit cells from the receiving animal&rsquo;s heart and support cell proliferation, matrix remodeling, tissue regeneration, and even animal growth. While these valves are safe and effective, their manufacturing remains complex and expensive as human cells must be cultured for a long time under heavily regulated conditions. The JetValve&rsquo;s much faster manufacturing process can be a game-changer in this respect. If we can replicate these results in humans, this technology could have invaluable benefits in minimizing the number of pediatric re-operations,&rdquo; said Hoerstrup.

In rotary jet spinning technology, a rotating nozzle extrudes a solution of extracellular matrix (ECM) into nanofibers that wrap themselves around heart valve-shaped mandrels. By using a series of mandrels with different sizes, the manufacturing process becomes fully scalable and is able to provide JetValves for all age groups and heart sizes. (Photo courtesy of Wyss Institute at Harvard University)

Harvard and the University of Zurich partner to create a next-generation heart valve that accurately functions upon implantation and regenerates into long-lasting heart-like tissue

Engineering heart valves for the many

<a href="http://eas.caltech.edu/people/mgharib" target="_blank">Mory Gharib</a> (PhD &#39;83), the Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering in the Division of Engineering and Applied Science, and postdoctoral researcher Chris Roh (MS &#39;13, PhD &#39;17) studied Anisopteran dragonfly larvae, which live in water and both breathe and move by inhaling water, extracting oxygen from it, and then expelling the water back out through a tri-leaflet anal valve that is surprisingly similar in structure to tricuspid human heart valves.&nbsp;The larvae are able to control the retraction of each of the three leaves individually, and this, Gharib and Roh discovered, gives them fine control over the size and symmetry (or asymmetry) of the valve opening.&nbsp;&quot;The dragonfly larva is the only insect that uses jet propulsion to move and the only arthropod known to use reciprocal jetting&mdash;inhaling and exhaling through the same orifice&mdash;for underwater breathing,&quot; says Roh, the lead author of a paper on the larval jets that was published online by the journal Bioinspiration &amp; Biomimeticson May 30.&nbsp;To observe how the larvae directed the flow of water using the leaves on their anal valves, Gharib and Roh set up high-speed cameras around an aquarium filled with a colored dye and tethered 96 dragonfly larvae&mdash;one at a time&mdash;in front of the cameras using dental wax. They found that when the larvae retracted all three leaves, the water jet flows straight out, pushing the animals straight forward. Retracting just one or two leaves, on the other hand, results in an asymmetric flow, which the larvae use when breathing.&quot;The way the dragonfly larvae use their unique adaptation to control the jet direction has previously been overlooked,&quot; says Gharib, senior author of the paper. &quot;The asymmetry control by the larvae is an intriguing jet-vectoring mechanism, different from those of squids or salps that simply point their funnels or siphons in a desired direction.&quot;Like the anus of the dragonfly larvae, heart valves have two or three leaves (depending on the valve) that control the flow. Gharib and Roh intend to use what they have learned from the dragonflies to engineer a new prosthetic multi-leaf heart valve that can direct jets in specific directions that mimic natural blood flow emerging from the valve, which is never perfectly symmetric. Currently, the unnaturally symmetrical flow of blood emerging from prosthetic valves can cause blood clots to form or even be abrasive to the walls of blood vessels. To cope with this unintended side effect of prosthetic heart valves, patients typically must spend the rest of their lives taking blood-thinning medications.&nbsp;&quot;The current heart valve design is a one-size-fits-all, where no patient-specific design is considered, and this causes many post-transplant complications,&quot; Roh says. &quot;We believe that an intentionally off-centered opening of the heart valve to more closely match the patient&#39;s original blood flow will be an important design parameter that can be adjusted based on each patient&#39;s heart morphology.&quot;

Seen as a light-colored plume, water jets out from the back of a larval dragonfly. Credit: Chris Roh and Mory Gharib/Caltech

A new understanding of the mechanics of dragonfly larvae respiration and maneuvering could lead to the next generation of prosthetic heart valves, say Caltech engineers.

Dragonfly Larvae Inspire New Designs for Prosthetic Heart Valves

Rear view of the ankle-assisting exosuits with its soft robotic elements and the cable that transfers mechanical power from actuators operated from the hip to the ankle join. (Image courtesy of the Rolex Awards/Fred Merz)

A soft wearable robotic suit promotes normal walking in stroke patients, opening new approaches to gait re-training and rehabilitation

Post-stroke patients reach terra firma with exosuit technology

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A commercial robotic leg could potentially benefit both higher- and lower-mobility amputees, University of Michigan roboticists have shown for the first time. The leg provided the largest gains when the U-M team applied its own control strategy, enabling a more symmetrical gait, lower tripping risks and a reduction in strain on the study participants’ sound legs and hips.The Michigan team worked with <a href="https://www.ossur.com/en-us/prosthetics/knees/power-knee" target="_blank" rel="noreferrer noopener">Össur’s Power Knee</a>, provided by the company, with primary funding from the National Institutes of Health.  Multiple robotic prosthetic legs are on the market but aren’t yet in wide clinical use. For many activities, the lightness and simplicity of passive legs is preferred by prosthesis users. However, for particularly taxing activities like rising from a chair, climbing stairs and hills, and walking long distances, the addition of power has the potential to help prosthesis users be more active while also preventing overuse injuries. <img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1760741246223-preliminary-test-OssurLeg.jpg" style="width:100%px" class="fr-fic fr-dib" />Study co-author Andrew Seelhoff, a PhD student in mechanical engineering, tests out a control algorithm on an Össur Power Knee, January 19th, 2024. Kevin Best (left), study first author, and senior author Robert Gregg (right) walk alongside him. The study results showed that the robotic prosthetic leg offered benefits for both high and low mobility prosthesis users. Credit: Brenda Ahearn/Michigan Engineering“The passive leg has a huge advantage in this study because the participants use it every day and are very used to its behaviors. Our study participants had just two training sessions with the powered leg. Even with that disadvantage, we observed benefits of the powered leg with both our controller and Össur’s,” said <a href="https://robotics.umich.edu/people/faculty/robert-gregg/" target="_blank" rel="noreferrer noopener">Robert Gregg</a>, a professor of robotics and corresponding author of the study in the Journal of NeuroEngineering and Rehabilitation.“Our study is significant because evidence was previously lacking for benefits of robotic knees over advanced passive knees, which is a big reason insurance companies don’t typically cover robotic knees. Our results begin to provide this evidence.”<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1760741273824-powerknee-best-seelhoff-OssurLeg.jpg" style="width:100%px" class="fr-fic fr-dib" />Kevin Best, first author of the study, observes Andrew Seelhoff, mechanical engineering PhD student and study co-author, setting up the Össur Power Knee in the Locomotor Control Systems Laboratory on May 15, 2024. The study results showed that the robotic prosthetic leg offered benefits for both high and low mobility prosthesis users. Credit: Brenda Ahearn/Michigan EngineeringIn this initial study, the researchers focused on key activities of daily living in which a powered prosthesis could provide meaningful benefits compared to passive knee prostheses. Study participants repeatedly sat and stood; walked quickly on a treadmill; and repeatedly sat in a chair, walked and sat down again. Prosthesis users who required extra walking assistance, such as a cane, found that the Power Knee offered significant help in all these tasks. Those who get around more easily on their own prostheses saw the most improvement in their gaits when Gregg’s team implemented their own control algorithm on Össur’s leg. One recent amputee described it as the closest they’d felt to two-legged walking on a prosthesis.“Our goal in prosthesis control is to make the leg behave as close as possible to the missing human limb in order to prevent compensations that often lead to overuse injuries. It also matters because gait deviations can bring unwanted attention to some users,” said <a href="https://neurobionics.robotics.umich.edu/profiles/kevin-best-bs/" target="_blank" rel="noreferrer noopener">Kevin Best</a>, a research associate in robotics, recent U-M robotics PhD graduate and first author of the study.The team investigated two fundamentally different control approaches. Össur’s more conventional controller relies on recognizing specific features of the user’s motion, indicating what they’re about to do. This makes the system very safe and predictable but may not always keep up with the user’s intent, Gregg said. In order to sit, users have to wait for the knee to recognize the sitting motion before it will bend, and likewise with standing.In contrast, the control approach developed by Gregg’s team continually adjusts to the user’s motion. They built mathematical models of how humans move, based on large datasets of unimpaired individuals. At each moment in time, their control algorithm measures the user’s thigh motion to determine the right behavior, creating more natural knee motions that are better synchronized with the user. <iframe width="640" height="360" src="https://www.youtube.com/embed/9LqZiai--ME?&amp;wmode=opaque&amp;rel=0&amp;enablejsapi=1&amp;origin=https://www.wevolver.com" frameborder="0"></iframe>“With the improvements in robotic devices, it is clear that robotic prostheses offer great promise to the amputee population,” said Jeff Wensman, a certified prosthetist/orthotist at Michigan Medicine and study co-author. “I am excited to see the advancement of a strategy to provide powered prosthesis users with user-synchronized control. I believe that this is a missing link to making powered prosthetics a reality for amputees.”This new control algorithm is harder to learn after using a conventional prosthesis for years, but the repeated sit-to-stand trials showed that participants were learning. Rather than getting more tired with each trial, they got faster. Then while walking, the more mobile group showed two improvements that could become significant benefits.<iframe width="640" height="360" src="https://www.youtube.com/embed/uo8zT7uXKCg?&amp;wmode=opaque&amp;rel=0&amp;enablejsapi=1&amp;origin=https://www.wevolver.com" frameborder="0"></iframe>First, they lifted the toe of the prosthetic foot higher, reducing the risk of tripping over small obstacles or rougher terrain. Second, they didn’t need to swing their hips as hard to move the prosthetic leg forward, hinting that the powered knee and lifelike control algorithm could potentially reduce back pain and allow users to go farther before getting tired, though the team couldn’t measure this with the short study. Next, the team hopes to demonstrate the safety and effectiveness of their control algorithm with stairs and ramps, followed by take-home tests. With more time to practice, the participants may be able to achieve even more. If the control strategy is successful, Össur could incorporate aspects of it into its own algorithm.For now, the improvements with Össur’s own algorithm were enough for two of the study participants to switch to the Power Knee for their everyday prosthesis, demonstrating that robotic prostheses are moving from laboratory exploration to real-world benefit.Primary funding by the National Institutes of Health was under award No. R01HD094772, with additional support from the National Science Foundation. Össur provided initial financial support and may have a financial interest in the results.The team has applied for patent protection for their controller with the assistance of U-M Innovation Partnerships.

Paired with custom control software, Össur's powered knee prosthesis helped study participants sit, stand and walk more easily.

Expanding a commercial robotic prosthetic leg's benefits with advanced control

“From the moment I woke up at the hospital after my accident, I could still feel my missing hand,” says Massimo Munzi. “I’ve been working on controlling my phantom hand with my mind ever since, contracting the muscles of my missing hands and fingers, mentally training just in case.”…just in case the right bionic technology becomes available. Convinced that commercial prosthetics can be improved, Munzi is invested in ongoing projects to develop bionic technology in a collaboration between EPFL and INAIL Hospital in Italy.If a research project owes its success to objective factors – excellence, financial resources, the working environment, etc. – it also owes it to an important element that cannot be controlled: the human one. An idea, a desire, a coincidence, or an encounter is sometimes all it takes to make progress, as demonstrated by Munzi, a hand amputee, and Jonathan Muheim, a doctoral student at EPFL. Their personal motivations came together, driving neuroprosthetics research forwards.<h2>From accident to being a part of a research community</h2>In 1990, Munzi was working in the agriculture industry. On the terrain, his hand got caught in the gears of a laboring tractor as he was trying to free a large piece of fabric that got stuck there. His hand was amputated soon afterwards. He currently works in a supermarket, responsible for the cashiers and inventory.“I’ve always wanted to improve prosthetics and get involved in a research project,” explains Munzi. “I’d like to help improve control, towards imitating a healthy hand, that’s why I never stopped training my phantom hand, my body and my mind, to be the best possible candidate for developing new technology, to help other amputees and myself one day.”In 2020, his idea became reality when during one of his usual check-ups for his prosthetic hand at INAIL center, in Bologna, Massimo encountered a research team from EPFL. Munzi volunteered for a first experiment, then started to work with Jonathan Muheim, an EPFL robotics Master’s student at the time, and Francesco Iberite a PhD student from Scuola Superiore Sant’Anna, who were investigating phantom temperature sensations supervised by Solaiman Shokur and Silvestro Micera of the Translational Neural Engineering Lab at EPFL’s Neuro-X.The team co-authored a study published in Science in 2023 that restores feelings of warmth and cold in the phantom hand of amputees, the basis for Muheim’s Master’s thesis for which he received the SSBE Student Award (Swiss Society for Biomedical Engineering). Muheim recently received the enable grant from EPFL’s Tech Transfer Office to further develop the device, and a start-up in Italy will be integrating the technology into commercial prosthetics for amputees.“Some of our tests are long and boring, and volunteers like Munzi stay committed and focused,” says Muheim who is now a doctoral student developing some of the first socially-oriented bionic technology. “Massimo can feel his phantom hand, sadly this is not the case for all amputees, which is why it is so precious to work with him.”The amputee regularly participates in experiments with non-invasive prosthetic technology, ranging from temperature feedback to exploratory experiments about other sensory feedback, sometimes coming to Geneva at Campus Biotech days at a time.“Massimo takes holiday time to come to Geneva for the experiments. He doesn’t speak the language. He’s full of determination. He’s a devoted grandfather, yet leaves everything behind to help out. It’s really a gift to work with Massimo,” says Muheim.<h2>Prosthetic technology that improves social interactions</h2>“There’s a very big bias in the field of robotic prosthetic hands towards motor function, like more degrees of freedom or improved controllability, but this is only part of the problem that will, for example, not help in social interactions,” says Muheim. “If you want to build a prosthetic hand that truly replaces your missing limb, you have to be able to feel, to touch and feel warmth. As Rochelle Ackerley from Marseille says, ‘Touch without temperature is like vision without color.’”Muheim investigates questions about sensory feedback in prosthetics, like ways to discriminate what you’re touching, psychological and social aspects of warmth, and exploring what Muheim calls “the whole experience of having a limb.” The researcher, who holds a Master’s in robotics with a minor in neuroprosthetics, got involved in biotechnology one step at a time: “I never thought of myself as a scientist. I’m more of an engineer who fell in love with a project that involves doing scientific research. I’m motivated by solving patients’ problems and making helpful devices.”“My first research experience was for a semester project with Stéphanie P. Lacour, head of the Laboratory for Soft Bioelectronic Interfaces at EPFL. There were so many cool projects, I was immersed in an environment of researchers who love what they do,” says Muheim. He got hooked on developing socially-oriented technology when, for EPFL’s MAKE Assistive Technology Challenge that aims to help someone with a disability, he and team members developed a device to facilitate communication of a 9 year old boy living with a severe motor impairment. “After leaving the device at home with him, his mother called us to say that she heard a computerized voice call ‘Mom’. She told us that it was the first time she had ever heard her son call for her. It’s amazing that you can develop something with your hands that can have a positive impact on someone’s life,” beams Muheim. “On the social aspect of technology, <a href="https://www.ted.com/talks/dr_solaiman_shokur_science_will_disappoint_you_until_it_doesn_t" target="_blank" rel="noopener">Solaiman Shokur’s TED talk</a> was an inspiration for me. I knew then that I had to do a project with Solaiman. That’s how I ended up doing my master’s thesis on bionic temperature feedback.”<h2>Community of scientists working together for social biotechnology</h2>Muheim is part of a growing community of researchers and patients involved in projects that marry social considerations with biotechnology. He has worked with as many as thirty patients for his research, including Munzi, most of them from Italy, bringing people of different walks across Europe for a common goal. “We develop ties with these people. They welcome us into their homes, participate in our experiments, provide valuable feedback. These periods are super intense for all of us, but it’s our common passion for the projects that brings us together and creates bonds. It’s motivational to see their level of commitment,” says Muheim.

The human determinants of research are key for making progress, as championed by amputee Massimo Munzi who is helping improve prosthetics, as well as EPFL's neuroprosthetic researcher Jonathan Muheim.

Amputee and researcher go prosthetic hand in hand towards progress

MIT researchers have developed a new bionic knee that can help people with above-the-knee amputations walk faster, climb stairs, and avoid obstacles more easily than they could with a traditional prosthesis.Unlike prostheses in which the residual limb sits within a socket, the new system is directly integrated with the user’s muscle and bone tissue. This enables greater stability and gives the user much more control over the movement of the prosthesis.Participants in a small clinical study also reported that the limb felt more like a part of their own body, compared to people who had more traditional above-the-knee amputations.“A prosthesis that's tissue-integrated — anchored to the bone and directly controlled by the nervous system — is not merely a lifeless, separate device, but rather a system that is carefully integrated into human physiology, offering a greater level of prosthetic embodiment. It’s not simply a tool that the human employs, but rather an integral part of self,” 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.Tony Shu PhD ’24 is the lead author of the <a href="http://doi.org/10.1126/science.adv3223" target="_blank">paper</a>, which appears today in Science.<iframe width="640" height="360" src="https://www.youtube.com/embed/ZQCVmuirYSI?&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">&nbsp;</iframe><h2 id="isPasted">Better control</h2>Over the past several years, Herr’s lab has been working on new prostheses that can extract neural information from muscles left behind after an amputation and use that information to help guide a prosthetic limb.During a traditional amputation, pairs of muscles that take turns stretching and contracting are usually severed, disrupting the normal agonist-antagonist relationship of the muscles. This disruption makes it very difficult for the nervous system to sense the position of a muscle and how fast it’s contracting.Using the new surgical approach developed by Herr and his colleagues, known as agonist-antagonist myoneuronal interface (AMI), muscle pairs are reconnected during surgery so that they still dynamically communicate with each other within the residual limb. This sensory feedback helps the wearer of the prosthesis to decide how to move the limb, and also generates electrical signals that can be used to control the prosthetic limb.In a <a href="https://news.mit.edu/2024/prosthesis-helps-people-with-amputation-walk-naturally-0701">2024 study</a>, the researchers showed that people with amputations below the knee who received the AMI surgery were able to walk faster and navigate around obstacles much more naturally than people with traditional below-the-knee amputations.In the new study, the researchers extended the approach to better serve people with amputations above the knee. They wanted to create a system that could not only read out signals from the muscles using AMI but also be integrated into the bone, offering more stability and better sensory feedback.To achieve that, the researchers developed a procedure to insert a titanium rod&nbsp;into the residual femur bone at the amputation site. This implant allows for better mechanical control and load bearing than a traditional prosthesis. Additionally, the implant contains 16 wires that collect information from electrodes located on the AMI muscles inside the body, which enables more accurate transduction of the signals coming from the muscles.This bone-integrated system, known as e-OPRA,&nbsp;transmits AMI signals to a new robotic controller developed specifically for this study. The controller uses this information to calculate the torque necessary to move the prosthesis the way that the user wants it to move.“All parts work together to better get information into and out of the body and better interface mechanically with the device,” Shu says. “We’re directly loading the skeleton, which is the part of the body that’s supposed to be loaded, as opposed to using sockets, which is uncomfortable and can lead to frequent skin infections.”In this study, two subjects received the combined AMI and e-OPRA system, known as an osseointegrated mechanoneural prosthesis (OMP). These users were compared with eight who had the AMI surgery but not the e-OPRA implant, and seven users who had neither AMI nor e-OPRA. All subjects took a turn at using an experimental powered knee prosthesis developed by the lab.The researchers measured the participants’ ability to perform several types of tasks, including bending the knee to a specified angle, climbing stairs, and stepping over obstacles. In most of these tasks, users with the OMP system performed better than the subjects who had the AMI surgery but not the e-OPRA implant, and much better than users of traditional prostheses.“This paper represents the fulfillment of a vision that the scientific community has had for a long time — the implementation and demonstration of a fully physiologically integrated, volitionally controlled robotic leg,” says Michael Goldfarb, a professor of mechanical engineering and director of the Center for Intelligent Mechatronics at Vanderbilt University, who was not involved in the research. “This is really difficult work, and the authors deserve tremendous credit for their efforts in realizing such a challenging goal.”<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1752710986929-MIT_Bionic-Knee-02-press.jpg" style="width: 100%px;" class="fr-fic fr-dib">A subject with the osseointegrated mechanoneural prosthesis overcomes an obstacle placed in their walking path by volitionally flexing and extending their phantom knee joint. Control signals from their residual knee muscles are used to produce movement of the powered prosthetic knee that mirrors the phantom knee. Credit: Courtesy of the researchers<h2>A sense of embodiment</h2>In addition to testing gait and other movements, the researchers also asked questions designed to evaluate participants’ sense of embodiment — that is, to what extent their prosthetic limb felt like a part of their own body.Questions included whether the patients felt as if they had two legs, if they felt as if the prosthesis was part of their body, and if they felt in control of the prosthesis. Each question was designed to evaluate the participants’ feelings of agency, ownership of device, and body representation.The researchers found that as the study went on, the two participants with the OMP showed much greater increases in their feelings of agency and ownership than the other subjects.“Another reason this paper is significant is that it looks into these embodiment questions and it shows large improvements in that sensation of embodiment,” Herr says. “No matter how sophisticated you make the AI systems of a robotic prosthesis, it’s still going to feel like a tool to the user, like an external device. But with this tissue-integrated approach, when you ask the human user what is their body, the more it’s integrated, the more they’re going to say the prosthesis is actually part of self.”The AMI procedure is now done routinely on patients with below-the-knee amputations at Brigham and Women’s Hospital, and Herr expects it will soon become the standard for above-the-knee amputations as well. The combined OMP system will need larger clinical trials to receive FDA approval for commercial use, which Herr expects may take about five years.

The new bionic knee can help people with above-the-knee amputations walk faster, climb stairs, and avoid obstacles more easily than they could with a traditional prosthesis. The new system is directly integrated with the user’s muscle and bone tissue (bottom row right). This enables greater stability and gives the user much more control over the movement of the prosthesis. Credit: Courtesy of the researchers; MIT News

In a small clinical study, users of this prosthesis navigated more easily and said the limb felt more like part of their body.

A bionic knee integrated into tissue can restore natural movement

In the holiday movie The Grinch, makeup artists are reported to have spent several hours each day encasing Jim Carrey’s face with prosthetics to create the iconic grumpy, green-furred creature. Such elaborate prosthetics, often made possible by materials like silicone rubbers, may have now found an unexpected yet beneficial biomedical engineering application, according to a new study from Texas A&amp;M University.<a href="https://www.nature.com/articles/s41598-024-76652-y" rel="noopener" target="_blank">Published in the journal Scientific Reports</a>,&nbsp;researchers have created realistic, skin-like replicas made of Ecoflex, a type of silicone rubber that can potentially serve as a platform to evaluate risks of bacterial infections from intravenous catheters and test wearable sensors, among other biomedical applications. The study found that EcoFlex-based skin replicas can be engineered to mimic actual skin textures, wettability, and elasticity, simulating the conditions where bacteria grow and adhere.“We think that the material holds tremendous promise for studying infections at the insertion site due to bacteria that are naturally occurring on the skin,” said Majed Othman Althumayri, a graduate student in the Texas A&amp;M Department of Biomedical Engineering and primary author of the paper. “Our goal was to create a skin-like material with ingredients that can be purchased off the shelf. Ecoflex is not just easy to use, it can be cured quickly with minimum additional steps, making it very convenient.”&nbsp;There are roughly a million bacteria per square centimeter of human skin. The most common of them is Staphylococcus, particularly the species Staphylococcus epidermidis, which is considered a typical resident of the skin microbiome. Infections often happen when there is a cut, break or wound on the skin, allowing the bacteria to enter the bloodstream. In fact, a relatively common infection in hospitals comes from surgically inserting tubes or catheters into veins. Each year, around 80,000 catheter-related bloodstream infections happen in intensive care units alone, underscoring its public health significance in the United States.“We have been slow in finding solutions for preventing infections from intravenous catheters,” said Althumayri. “A reason could be that we lack good platforms to test new catheter designs or &nbsp;wearable biosensor technologies and train staff so that the number of infections can be reduced.”&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734481767784-News-BMEN-Hands3Long-16Dec2024.jpg" style="width: 100%px;" class="fr-fic fr-dib">Hand replica made of Ecoflex. | Image:&nbsp;<cite id="isPasted">Courtesy of Majed Othman Althumayri</cite>To address this gap, the researchers turned to Ecoflex 00-35, a fast-curing, biocompatible rubber used for various applications, including prosthetics for special effects. First, they created molds of common intravenous insertion sites, such as the elbows, hands and forearms. Then, by pouring Ecoflex into the molds that contained artificial bones and tubes acting as veins, the researchers created skin-like replicas.&nbsp;Next, the researchers tested if the Ecoflex skin replicas had properties that matched that of real skin. They measured the replicas’ wettability, bacterial adhesion and mechanical properties, such as elasticity and resilience. The researchers found that the Ecoflex models could replicate human skin roughness within a 7.5% error margin. Further, high-resolution imaging showed that bacteria could adhere to the skin replica and grow on it.&nbsp;Then, in a key experiment, the researchers simulated an intravenous catheter insertion into an Ecoflex hand replica that they created. This artificial hand effectively modeled phases of bacterial growth, showing promise that these replicas can be used for implementing infection control measures and improving the design of medical devices like catheters.However, the researchers noted that their current experiments do not entirely model real-world conditions.&nbsp;“Developing realistic skin models that can mimic the human skin is an important initial step,” said Dr. Hatice Ceylan Koydemir, corresponding author on the study and assistant professor in the Department of Biomedical Engineering with a research program housed within the Texas A&amp;M University Center for Remote Health Technologies and Systems. “But we think that incorporating additional elements, like body fluids and other clinically relevant situations, in future experiments will bolster our findings and further validate Ecoflex’s potential for medical applications.”Other contributors to the research include Azra Yaprak Tarman, a graduate student in the Department of Biomedical Engineering.This study was partly sponsored by the National Institute of General Medical Sciences (one of the National Institutes of Health), the Department of Defense Office of Naval Research and the National Science Foundation-funded&nbsp;<a href="https://tees.tamu.edu/research/initiatives/paths-up.html" rel="noopener" target="_blank">Engineering Research Center PATHS-UP</a>. Researchers also received additional support from the Department of Biomedical Engineering, the Center for Remote Health Technologies and Systems, the Texas A&amp;M Engineering Experiment Station, the AggieFab Nanofabrication Facility, and the Soft Matter Facility.

Graduate student Majed Othman Althumayri demonstrates an Ecoflex cast of his hand. | Image: Emily Oswald/Texas A&M Engineering

prosthetics & bionics

TAGGED WITH bionics