Textile prostheses in the medal race at the Paralympics

The Paralympics are currently taking place in Beijing. Numerous athletes are once again hunting for medals there with high-tech prostheses made of fibers. Ilke Wyludda is also interested in the textile helpers. The Olympic champion has already taken part in the Paralympics herself after a transfemoral amputation. A call with an Olympian who knows almost as much about the importance of fibers in elite sports as she does about medals.

“I look very closely at which prostheses are used in the Paralympics,” says Ilke Wyludda. “The technology has advanced incredibly in recent years.” One immediately notices about the Leipzig native: Here is not just a former professional athlete feverishly watching, here is a connoisseur looking at the fiber aids of para-athletes. Wyludda knows their current competitive feelings from her own experience. In 1996, she competed at the Olympic Games in Atlanta. She threw the discus, which weighed around one kilogram, 69.66 meters across the Olympic lawn: Gold medal! (Here is a qualifying throw) A few years later, she ended her active sports career and began studying medicine. Then, in 2010, she had to have her right transfemoral amputated due to an infection. From now on, prostheses are part of her life. She met Rocco Bartel and Jörg Schad at the medical supply store where they were made. Bartel is a master orthopedic technician, Schad a technician – both are specialists in fiber composite aids. The three have no idea yet that this is the starting signal for a trio of fiber Olympic successes.

“Handicap as a challenge”

A year and a half after the operation, Wyludda’s sporting ambition flares up again. “I did not want to see my new handicap as a limitation, but as a challenge,” she says. Her competition debut is to be the 2012 Paralympics in London. However, she will not be able to compete in her favorite discipline, the discus, and will therefore switch to the shot put. She had also trained in the shot put in the past, but never competed in it at Olympic level. But Wyludda is a fighter, saying, “When I start something, I don’t just want to participate.” At that time, the fiber composite technicians Bartel and Schad should also participate. A quarter of a year before the Paralympics, Wyludda asks them, “Can you help me develop a prosthesis for the Paralympics?” They can.

In search of the perfect fiber solution

From now on, the three meet regularly. Among other things, Wyludda needs a special throwing frame from which she can push the ball while sitting. The optimal material for this is quickly found: Carbon fibers. “It is practically a standard material in the sports prosthesis sector,” says Bartel. One reason for this is that carbon fibers are strong and light at the same time, even with a small amount of material. In addition, Bartel says, they absorb and release energy very well. “You can think of it a bit like a spring.” Generally, the prostheses are custom-made, individually tailored to the particular sport and athlete. “These are not prostheses that you can comfortably walk around with in everyday life,” says Bartel.

For months, Wyludda and the two fiber composite specialists tinker with the perfect fiber solution. Wyludda tests the prototypes they build on the sports field, where she really “sweats” the small carbon fibers. As an experienced athlete, she knows exactly what is important. She finds weak points and notes down suggestions for improvement. She discusses both with the technicians. They then build a new prototype, and the game starts all over again. “It was tinkering at a high level,” recalls Olympic champion Wyludda. The three of them work on the Paralympic carbon throwing frame until a week before their departure for London.

The moment of truth

Then comes the moment of truth. As an Olympic champion, Ilke Wyludda is the experienced one at the Paralympics. But in disabled sports she is a newcomer. In the end, she ends up in 5th place. Was she disappointed? “I think I did well,” she says today. In subsequent years, she takes silver in the shot put at European Championships and bronze in the discus throw at the 2015 World Championships. Her ultimate tip on how to make it to the podium: “Approach the competition with joy,” says the Olympian, who has been working as an anesthesiologist since 2011.

Using sensors to improve prosthesis wearing comfort?

Wyludda and Bartel have become friends. To this day, the two are poring over new prostheses and improvements for external carbon fiber aids. The medical supply company that Bartel and his colleague Schad worked for at the time was taken over at some point by the company REHA aktiv 2000 from Jena.

There, master technician Bartel is now also working on prostheses made of hemp, flax and basalt fibers. But one question in particular is currently driving him: Can the trial-and-error phase in the search for the right prosthesis shape be shortened with sensors? And thus improve wearing comfort? “Up to now, the production of prostheses has primarily relied on empirical values,” explains Bartel. But what if sensors inside the fiber composite provided real-time information about the condition of the prosthesis? Could they help provide answers to questions like: Where is the prosthesis pressing on the patient? Where can it be relieved? Where do which forces act and how strongly?

Remembering the shape of fibers

To this end, Bartel is conducting research with partners such as the Fraunhofer Institute for Machine Tools and Forming Technology in Chemnitz in a project funded by the German Federal Ministry of Research. The project involves special strain sensors for prostheses and orthoses. The Chemnitz-based company FiberCheck, which is also involved in the project, is behind the sensor technology used. Managing Director Tobias Meyhöfer and his team are using so-called shape memory alloys (FGL). These are materials that change their state when stretched or subjected to temperature changes. Made of nickel or titanium, such alloys have been in use since the 1980s, for example in stents, surgical tools or dental braces. But FGLs made of metal cannot be technologically transferred one-to-one to textiles, according to Meyhöfer. “Fiber composites are stretchable,” he says. And explains, “For a strain measurement to provide information from inside a prosthesis made of fiber composite, we need sensors that stretch along with it.” Although metallic or printed sensors for textile prostheses already exist, says the FiberCheck boss, their flexibility is limited.

Before the patented sensor delivers data from inside fiber composite prostheses, it is first stitched onto a fleece or fabric / Source: Sascha Linke

Real-time feedback for optimal prosthesis use

Installed inside a carbon prosthesis, the FGL strain sensors are designed to register loads and unloads in real time. In other words, if the patient loads the prosthesis, the FGL sensor changes shape; if the load subsides, it returns to its original state. Experts call this superelasticity. Thanks to it, the sensors should provide data from inside prostheses that was previously impossible to get at. “Our FGL sensors measure resistance changes 2.5 times more strongly than conventional strain sensors,” says Meyhöfer. If he and his project partners have their way, the sensor system will in the future use sound or vibration to communicate where pressure points are located between the body and the prosthesis, what posture is optimal and when there is a risk of overloading the material. Patients who have to learn how to use a prosthesis should thus be able to start their new lives more quickly. “Our goal is to make wearing the prosthesis as comfortable as possible,” says Meyhöfer. So in the future, the sensors could significantly shorten the experience-based trial-and-error that Olympian Wyludda and fiber composite technicians Bartel and Schad engaged in on their way to the Paralympics.