Sarah’s Bionic Hand | Health and wellness
The second says: Sergio Sanchez and Javier Blanco, both 26 years old and from Madrid, have always been friends “since school”. In 2020, they were studying a master’s degree in 3D printing and advanced manufacturing together when they decided their master’s thesis (TFM) could be used to help their friend Sarah Martin. The 24-year-old was born without her forearm and left hand and they made a prosthesis for both limbs. “We wanted to mix engineering and medicine. We proposed it to Sarah and she immediately said ‘yes,’” they said excitedly.
Three years later, they are already on the second version: “I started using the previous model, but they immediately told me they could improve it,” says the young woman from Madrid. The first prosthesis they developed was mechanical. I worked through some cables that attached Martine’s elbow to the prosthetic hand, so that when the elbow bent, the hand closed. The second version is electrocautery. In other words, it contains electronics and has two electrodes that are attached to the flexor and extensor muscles of the hand, on the arm, to perform the movements of opening and closing the hand.
“We take a muscle that has no function, because there is no limb, and we give it to it thanks to the sensors,” Blanco explains. Sensors transmitted through bluetooth Electrical signals issued by the muscles of the mobile phone that convert them into specific commands. In this way, when Martin squeezes a muscle, the hand opens or closes.
The woman from Madrid had used other cosmetic tips before, without functions, but she didn’t like it. “It was very heavy and artificial and eventually I got used to not wearing it,” says the young woman. I’ve also tried other muscle electric models, but they had the same problem with weight, it was too big for it and it “cost too much”. Martine complains that although there is help, not all models are eligible for it and funding is tight.
One of the advantages of 3D printing technology in such cases is that it reduces costs. Not counting the working hours, Blanco and Sanchez calculated that the cost of manufacturing the first prosthesis is about 60 or 80 euros. In the second case, since it is a more complex system, the amount could amount to about 200 euros, although this figure has not been specified because the photovoltaic prototype is not finished yet and they are still making modifications.
Being a TFM project, the vast majority of the costs were borne by the center where they were studying, the EDDM Engineering School in Madrid, so they did not have to make any economic contribution. They assume that if their prototype turns into a real product, the final selling price will be €1,000 for the first model and €1,500 for the second.
Before starting the project, they conducted a market study to see what investment this type of prosthesis could entail. They will cost about 2,300 and 4,000 euros, respectively, a calculation they made with the prices of the catalog of orthopedic services at the Ministry of Health. However, Blanco acknowledges that “the prices quoted there are much lower than the real ones.”
Another advantage of this technology is that it allows for a fairly high degree of customization, as the three guys point out. “The important thing is that it was the most helpful and comforting for Sarah,” Sanchez explains with conviction. To manufacture the prosthesis, they swabbed Martyn’s right arm and hand to take measurements and make it as symmetrical as possible. They also talked with the young woman about what to expect and what they could improve from previous experiences she had. The end result consists of 28 pieces on the fingers, three on the hand, two on the forearm and two hooks.
The first afternoon that Sarah tried on the prosthesis, she took great control of it.
Sergio Sanchez, creator of the prosthesis
The two students point out that it took the young woman very little to learn how to use her first prosthesis. “We expected it to take a few days to get used to, but the first afternoon I tried it, it handled great,” Blanco says proudly. For his part, Martin expressed the difficulty involved: “You have to learn to control muscles that you don’t use regularly.”
The young woman talks about the improvement it has made to her daily life, even though she “doesn’t need it to live.” Unlike the previous devices he used, he says he now has a prosthesis that helps him and it’s really useful. Since it’s a project outside of their job, they can’t spend as much time on it as they like. Martin doesn’t have it yet because Sanchez and Blanco haven’t finished all the work and are still making some adjustments.
Alfonso Denia, founder and CEO of EDDM, explains that this is the first time that such a project has been developed at the center. “Everything related to biomedicine goes well because, in addition, it is a field that is seen in a master’s degree,” he says, and also highlights, like his students, the economic nature: “A 3D printer of thousands is not necessary in euros to be able to Do something like that.”
The work’s authors were clear in their desire to “do something that would really help someone, really benefit them.” After completing his master’s degree, Sanchez no longer has anything to do with orthopedics, he is dedicated to the aviation sector, but Blanco continues to train in this field: “I would like to continue to combine technology and science to improve people’s lives.”
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