High-tech "replacement Parts" Offer Hope To Millions

An accident or illness can mean learning to live with a missing limb, a defective organ, or damaged tissue, bones or joints. Researchers at EPFL and elsewhere are working on new solutions to make life more comfortable for the millions of afflicted people around the world.

EPFL's Translational Neural Engineering Laboratory, headed by Silvestro Micera, has made a name for itself for more than a decade, notably for its work on prosthetic hands. In 2023, the research group made a major step forward by developing a new sensory feedback method that uses noninvasive thermal electrodes to allow amputees to feel warmth in their missing hand. "Temperature feedback is essential for relaying information that goes beyond touch," said Micera at the time. "It leads to feelings of affection. We're social beings and warmth is an important part of that."

TNE bioengineer Vincent Mendez, who's based at Campus Biotech in Geneva, is one of the researchers at the forefront of innovation in this field: "Right now, our group is working on a prosthesis that incorporates all the technology and capabilities we've developed in recent years - sensations of touch and warmth, plus robotic components," he says. "On the touch side, we've teamed up with colleagues from Scuola Superiore Sant'Anna in Pisa, Italy. They've developed a new, noninvasive system that, instead of relying on nerve implants, uses mini-balloons which inflate inside the attachment interface, touching the skin at specific points and creating the illusion that the phantom hand itself is being touched."

Artificial hands controlled by thought

For the past six years, Mendez has focused in particular on the question of control, working with patients to develop systems for commanding robotic hands with their mind. "We use electrodes on the forearm to measure muscle activity," he explains. "That lets us decipher and interpret the signals they transmit. The aim is to translate the person's intention into an intuitive, natural movement." Mendez is hopeful that a prototype incorporating the new technology will be ready in 2026.

Another TNE researcher is Daniel Leal, a neuroengineer involved in the Third Arm Project, which aims to develop an "extra" robotic arm. As well as restoring some function to people who've lost the use of their upper limbs, the system could also prove useful to able-bodied people, helping them "multitask" or perform delicate medical or rescue operations. "One challenge is to find a way to control the extra arm using motor resources that are normally allocated to other bodily functions, without disrupting those functions," says Leal. "Our work involves harnessing the natural redundancies built into the human body."

The research group is exploring whether the robotic arms could be controlled by moving the diaphragm or the ears. "The ear muscles are vestigial, or remnants of evolutionary processes. Most people can no longer use them," says Leal. "But the neural connections still exist, so we can train the brain to reassign them. One advantage of these muscles is they can still be preserved in most cases of high-level spinal cord injury, making them suitable targets for neuroprosthetic control."

Hydrogels: promising potential for soft-tissue healing

Fortunately, not all accidents involve the loss of a limb. Injuries suffered at home or while playing sports often affect soft tissue such as skin, tendons and muscles. But even minor surgery can have mixed results, because this tissue tends to regenerate and heal poorly. Researchers have been trying for decades to develop adhesives capable of withstanding the stresses of the human body in motion. At EPFL's Laboratory of Biomechanical Orthopedics (LBO), Dominique Pioletti and his team are working on a new class of hydrogels - injectable biomaterials that can bind to tissue and help them regenerate.

As Pioletti explains, hydrogels offer a number of key advantages: "Just like soft tissue, hydrogels consist of a matrix of molecules that holds a liquid inside. Another advantage is they can be injected in liquid form and then partially solidified at a later stage, for example, in response to light, meaning they can be used in a minimally invasive way."

At the moment, the LBO researchers are focusing mainly on repairing cartilage defects. "Our colleagues at the Lausanne University Hospital (CHUV) treat cartilage injuries by extracting cells from the patient, expanding them in the lab, and then reinserting them to promote regrowth," says Pioletti. "For now, these cells are injected with a liquid, which causes some problems - especially when it comes to keeping them in place. But if they're inserted in a gel that binds to the cartilage, the cells will stay where they're supposed to be, leading to better therapeutic outcomes. The gel will both protect and merge with the existing tissue."

Treating damaged cartilage - a type of tissue whose texture Pioletti compares to chewing gum - is very much a race against time: "If the damaged area isn't protected, the body forms what's known as fibrocartilage. This disorganized fibrous tissue remains in the damaged area, preventing better-quality cartilage from growing back. But a hydrogel will fill the gap instead, allowing the tissue to regenerate." One of the major challenges with this approach is predicting how quickly the hydrogel will degrade.

Pioletti expects to have a commercially viable product ready in approximately five years. He was also involved in the creation of EPFL startup flowbone.

3D skin and muscle

LBO is not the only research group conducting pioneering research on hydrogels. Earlier this year, scientists at the Swiss Federal Laboratories for Materials Science and Technology (Empa) used gelatin derived from cold-water fish such as cod and pollock to develop a patented, innovative, non-swelling biomaterial that can be 3D-printed with skin cells to create living models. The hydrogel simulates the extracellular matrix and emulates the layered structure of human skin, allowing scientists to study diseases and chronic wounds. It could also be used as a dressing material: it's biologically compatible and causes fewer immune reactions than comparable materials based on mammalian gelatin.

Another Empa team is using 3D printing to produce artificial muscles. In March this year, the researchers announced a significant breakthrough, noting that these structures could one day "support people at work or when walking, or replace injured muscle tissue." The artificial muscles contain dielectric elastic actuators (DEAs), which are interlocked layers of silicone-based materials: one conductive, the other nonconductive. The actuator contracts like a muscle when an electrical voltage is applied, then relaxes when the voltage is switched off.

Healing hearts and spreading smiles

DEAs play an important role in the work of Yves Perriard, a microengineer based at the EPFL campus at Microcity in Neuchâtel. The two entities he heads - the Integrated Actuators Laboratory (LAI) and the Center for Artificial Muscles (CAM) - are working with engineers at the University of Zurich, the University of Bern and the Technical University of Munich to develop motors and soft robotic components that could assist those suffering from illness or injury.

Through their research focused on the heart - or, to be more exact, the aorta - the scientists are hoping to bring about a revolution in the treatment of heart failure. "At present, when we implant an artificial pump, rigid components such as metals and magnets have to be placed inside the heart," says Perriard. "Our goal is to create something soft and much less invasive - a pump that doesn't come into direct contact with the blood or enter the heart."

Perriard's team has developed a ring-shaped DEA that can be placed on the aorta where it joins the heart. "The ring expands and contracts," he explains. "By getting it to move in sync with the opening and closing of the aortic valve, we can create a suction effect that helps the heart to pump."

The method proved successful during initial in vito trials in pigs, conducted in 2021 and 2022. "And last year, we made a discovery that opened up a whole new world of possibilities," says Perriard. "By creating an air gap around the DEA, we were able to amplify its effect by a factor of almost ten. Rather than just helping the heart to beat, this system could, in fact, replace it altogether." The team has already patented this proprietary technology. "We're getting closer to the point where we can run human trials," says Perriard.

Perriard's labs are also collaborating with Nicole Lindenblatt's research group at University Hospital Zurich on facial reanimation treatments. "Our goal is to help people suffering from facial paralysis," he explains. "This condition, which often affects just one side of the face, can be caused by viruses that attack the nerves. Our system involves connecting a flat, extremely thin DEA to the zygomaticus major muscle beneath the cheek. It's controlled by an electronic device that reads and interprets nerve signals, restoring the patient's ability to raise the corner of their mouth." These advancements, and others like them, are set to put a smile back on millions of faces.