Being at one with your bionic leg

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Djurica Resanovic lost his leg in a motorbike accident several years ago which resulted in amputation above the knee. Thanks to novel neuroprosthetic leg technology, Resanovic was successfully merged with his bionic leg during clinical trials in Belgrade, Serbia.

“After all of these years, I could feel my leg and my foot again, as if it were my own leg,” reports Resanovic about the bionic leg prototype. “It was very interesting. You don’t need to concentrate to walk, you can just look forward and step. You don’t need to look at where your leg is to avoid falling.”

Walking with instinct again

Scientists from a European consortium led by Swiss Institutions, ETH Zurich and EPFL spin-off SensArs Neuroprosthetics, with clinical trials in collaboration with institutions in Belgrade, Serbia, successfully characterized and implemented bionic leg technology with three amputees. The results appear in today’s issue of Science Translational Medicine.

“We showed that less mental effort is needed to control the bionic leg because the amputee feels as though their prosthetic limb belongs to their own body,” explains Stanisa Raspopovic, ETH Zurich professor and co-founder of EPFL spin-off SensArs Neuroprosthetics, who led the study.

He continues, “This is the first prosthesis in the world for above-knee leg amputees equipped with sensory feedback. We show that the feedback is crucial for relieving the mental burden of wearing a prosthetic limb which, in turn, leads to improved performance and ease of use.”

Wearing a blindfold and earplugs, Resanovic could feel his/her bionic leg prototype thanks to sensory information that was delivered wirelessly via electrodes surgically placed into the stumps’ intact nervous system. These electrodes pierce through the intact tibial nerve instead of wrapping around it. This approach has already proven to be efficient for studies of the bionic hand led by Silvestro Micera, co-author of the publication, EPFL’s Bertarelli Foundation Chair in Translational Neuroengineering, professor of Bioelectronics at Scuola Superiore Sant’Anna, and co-founder of SensArs Neuroprosthetics. [See “How the bionic leg works: connection between body and machine”.]

Resanovic continues, “I could tell when they touched the [big toe], the heel, or anywhere else on the foot. I could even tell how much the knee was flexed.”

Resanovic is one of three leg amputees, all with transfemoral amputation, who participated in a three-month clinical study to test new bionic leg technology which literally takes neuroengineering a step forward, providing a promising new solution for this highly disabling condition that affects more than 4 million people in Europe and in the United-States.

Thanks to detailed sensations from sole of the artificial foot and from the artificial knee, all three patients could maneuver through obstacles without the burden of looking at their artificial limb as they walked. They could stumble over objects yet mitigate falling. Most importantly, brain imaging and psychophysical tests confirmed that the brain is less solicited with the bionic leg, leaving more mental capacity available to successfully complete the various tasks.

These results complement a recent study that demonstrated the clinical benefits of the bionic technology, like reducing phantom limb pain and fatigue.

Bionic leg: from prototype to product

“We develop the sensory feedback technology to augment prosthetic devices,” explains Francesco Petrini, CEO and co-founder of SensArs Neuroprosthetics, and who is guiding an effort to bring these technologies to market. “An investigation longer than 3 months, with more subjects, and with in-home assessment, should be executed to provide more robust data to draw clinically significant conclusions about an improvement of the health and quality of life of patients.” This project was funded in part by the NCCR Robotics and by the Bertarelli Foundation.

— How the bionic leg works: connection between body and machine

The fundamental neuroengineering principle is about merging body and machine. It involves imitating the electrical signals that the nervous system would have normally received from the person’s own, real leg. Specifically, the bionic leg prototype is equipped with 7 sensors all along the sole of the foot and 1 encoder at the knee that detects the angle of flexion. These sensors generate information about touch and movement from the prosthesis. Next, the raw signals are engineered via a smart algorithm into biosignals which are delivered into the stump’s nervous system, into the tibial nerve via intraneural electrodes, and these signals reach the brain for interpretation.

Intraneural electrodes are key for neuroprosthetics

“We believe intraneural electrodes are key for delivering bio-compatible information to the nervous system for a vast number of neuroprosthetic applications. Translation to the market is just around the corner”, explains Silvestro Micera, co-author of the publication, EPFL’s Bertarelli Foundation Chair in Translational Neuroengineering, professor of Bioelectronics at Scuola Superiore Sant’Anna, and co-founder of SensArs Neuroprosthetics. Micera continues to innovate in the field of translational neuroscience using intraneural electrodes, like the bionic hand, optic nerve stimulation, and vagus nerve stimulation for heart-transplant patients..

Learn more: Amputees merge with their bionic leg

 

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Merging user and robotic control in a smart artificial hand for amputees

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EPFL scientists have successfully tested new neuroprosthetic technology that combines robotic control with users’ voluntary control, opening avenues in the new interdisciplinary field of shared control for neuroprosthetic technologies.

EPFL scientists are developing new approaches for improved control of robotic hands – in particular for amputees – that combines individual finger control and automation for improved grasping and manipulation. This interdisciplinary proof-of-concept between neuroengineering and robotics was successfully tested on three amputees and seven healthy subjects. The results are published in today’s issue of Nature Machine Intelligence.

The technology merges two concepts from two different fields. Implementing them both together had never been done before for robotic hand control, and contributes to the emerging field of shared control in neuroprosthetics.

One concept, from neuroengineering, involves deciphering intended finger movement from muscular activity on the amputee’s stump for individual finger control of the prosthetic hand which has never before been done. The other, from robotics, allows the robotic hand to help take hold of objects and maintain contact with them for robust grasping.

“When you hold an object in your hand, and it starts to slip, you only have a couple of milliseconds to react,” explains Aude Billard who leads EPFL’s Learning Algorithms and Systems Laboratory. “The robotic hand has the ability to react within 400 milliseconds. Equipped with pressure sensors all along the fingers, it can react and stabilize the object before the brain can actually perceive that the object is slipping. ”

How shared control works

The algorithm first learns how to decode user intention and translates this into finger movement of the prosthetic hand. The amputee must perform a series of hand movements in order to train the algorithm that uses machine learning. Sensors placed on the amputee’s stump detect muscular activity, and the algorithm learns which hand movements correspond to which patterns of muscular activity. Once the user’s intended finger movements are understood, this information can be used to control individual fingers of the prosthetic hand.

“Because muscle signals can be noisy, we need a machine learning algorithm that extracts meaningful activity from those muscles and interprets them into movements,” says Katie Zhuang first author of the publication.

Next, the scientists engineered the algorithm so that robotic automation kicks in when the user tries to grasp an object. The algorithm tells the prosthetic hand to close its fingers when an object is in contact with sensors on the surface of the prosthetic hand. This automatic grasping is an adaptation from a previous study for robotic arms designed to deduce the shape of objects and grasp them based on tactile information alone, without the help of visual signals.

Many challenges remain to engineer the algorithm before it can be implemented in a commercially available prosthetic hand for amputees. For now, the algorithm is still being tested on a robot provided by an external party.

“Our shared approach to control robotic hands could be used in several neuroprosthetic applications such as bionic hand prostheses and brain-to-machine interfaces, increasing the clinical impact and usability of these devices,” says Silvestro Micera, EPFL’s Bertarelli Foundation Chair in Translational Neuroengineering, and Professor of Bioelectronics at Scuola Superiore Sant’Anna in Italy.

Learn more: A smart artificial hand for amputees merges user and robotic control

 

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Bioprinting complex living tissue in just seconds will revolutionize tissue engineering

Credit: Alain Herzog / 2019 EPFL

Researchers from EPFL and the University Medical Center Utrecht in the Netherlands have developed an extremely fast optical method for sculpting complex shapes in stem-cell-laden hydrogels and then vascularizing the resulting tissue. Their groundbreaking technique stands to change the field of tissue engineering.

Tissue engineers create artificial organs and tissues that can be used to develop and test new drugs, repair damaged tissue and even replace entire organs in the human body. However, current fabrication methods limit their ability to produce free-form shapes and achieve high cell viability.

Researchers at the Laboratory of Applied Photonics Devices (LAPD), in EPFL’s School of Engineering, working with colleagues from Utrecht University, have come up with an optical technique that takes just a few seconds to sculpt complex tissue shapes in a biocompatible hydrogel containing stem cells. The resulting tissue can then be vascularized by adding endothelial cells.

The team describes this high-resolution printing method in an article appearing in Advanced Materials. The technique will change the way cellular engineering specialists work, allowing them to create a new breed of personalized, functional bioprinted organs.

Printing a femur or a meniscus

The technique is called volumetric bioprinting. To create tissue, the researchers project a laser down a spinning tube filled with a stem-cell-laden hydrogel. They shape the tissue by focusing the energy from the light at specific locations, which then solidify. After just a few seconds, a complex 3D shape appears, suspended in the gel. The stem cells in the hydrogel are largely unaffected by this process. The researchers then introduce endothelial cells to vascularize the tissue.

The researchers have shown that it’s possible to create a tissue construct measuring several centimeters, which is a clinically useful size. Examples of their work include a valve similar to a heart valve, a meniscus and a complex-shaped part of the femur. They were also able to build interlocking structures.

“Unlike conventional bioprinting – a slow, layer-by-layer process – our technique is fast and offers greater design freedom without jeopardizing the cells’ viability,” says Damien Loterie, an LAPD researcher and one of the study’s coauthors.

Replicating the human body

The researchers’ work is a real game changer. “The characteristics of human tissue depend to a large extent on a highly sophisticated extracellular structure, and the ability to replicate this complexity could lead to a number of real clinical applications,” says Paul Delrot, another coauthor. Using this technique, labs could mass-produce artificial tissues or organs at unprecedented speed. This sort of replicability is essential when it comes to testing new drugs in vitro, and it could help obviate the need for animal testing – a clear ethical advantage as well as a way of reducing costs.

“This is just the beginning. We believe that our method is inherently scalable towards mass fabrication and could be used to produce a wide range of cellular tissue models, not to mention medical devices and personalized implants,” says Christophe Moser, the head of the LAPD.

The researchers plan to market their groundbreaking technique through a spin-off.

Learn more: Bioprinting complex living tissue in just a few seconds

 

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A tiny stretchable pump could launch the next generation of soft robots

Bending the pump Credit: Vito Cacucciolo / 2019 EPFL

Scientists at EPFL have developed a tiny pump that could play a big role in the development of autonomous soft robots, lightweight exoskeletons and smart clothing. Flexible, silent and weighing only one gram, it is poised to replace the rigid, noisy and bulky pumps currently used.

The scientists’ work has just been published in Nature.

Soft robots have a distinct advantage over their rigid forebears: they can adapt to complex environments, handle fragile objects and interact safely with humans. Made from silicone, rubber or other stretchable polymers, they are ideal for use in rehabilitation exoskeletons and robotic clothing. Soft bio-inspired robots could one day be deployed to explore remote or dangerous environments.

Most soft robots are actuated by rigid, noisy pumps that push fluids into the machines’ moving parts. Because they are connected to these bulky pumps by tubes, these robots have limited autonomy and are cumbersome to wear at best.

Cutting soft robots’ tether

Researchers in EPFL’s Soft Transducers Laboratory (LMTS) and Laboratory of Intelligent Systems (LIS), in collaboration with researchers at the Shibaura Institute of Technology in Tokyo, Japan, have developed the first entirely soft pump – even the electrodes are flexible. Weighing just one gram, the pump is completely silent and consumes very little power, which it gets from a 2 cm by 2 cm circuit that includes a rechargeable battery. “If we want to actuate larger robots, we connect several pumps together,” says Herbert Shea, the director of the LMTS at the School of Engineering.

This innovative pump could rid soft robots of their tethers. “We consider this a paradigm shift in the field of soft robotics,” adds Shea. The researchers have just published an article on their work in Nature.

Soft pumps can also be used to circulate liquids in thin flexible tubes embedded in smart clothing, leading to garments that can actively cool or heat different regions of the body. That would meet the needs of surgeons, athletes and pilots, for example.

How does it work?

The soft and stretchable pump is based on the physical mechanism used today to circulate the cooling liquid in systems like supercomputers. The pump has a tube-shaped channel, 1 mm in diameter, inside of which rows of electrodes are printed. The pump is filled with a dielectric liquid. When a voltage is applied, electrons jump from the electrodes to the liquid, giving some of the molecules an electrical charge. These molecules are subsequently attracted to other electrodes, pulling along the rest of the fluid through the tube with them. “We can speed up the flow by adjusting the electric field, yet it remains completely silent,” says Vito Cacucciolo, a post-doc at the LMTS and the lead author of the study.

Developing artificial muscles in Japan

The researchers have successfully implanted their pump in a type of robotic finger widely used in soft robotics labs. They are now collaborating with Koichi Suzumori’s laboratory in Japan, which is developing fluid-driven artificial muscles and flexible exoskeletons.

Learn and see more: A miniature stretchable pump for the next generation of soft robots

 

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