This Blog Post is From Our Friends at 3Ders and it was Written by Benedict -
Maker Bodo Hoenen has used 3D printing to make a robotic elbow for his daughter, Lorelei. After being diagnosed with AFM, a rare, polio-like condition, Lorelei suffered near-total paralysis of her upper left arm, but the 3D printed device is helping in her rehabilitation.
The wellness of one’s children is every parent’s number one priority. So when young and healthy Lorelei one day became ill, fighting to breathe and unable to move her body, her father Bodo was understandably incredibly fearful. Lorelei pulled through, but was diagnosed with AFM, a polio-like condition that causes elevated brain and spinal pressure, and suffered near-total paralysis of her upper left arm. Sadly, success in rehabilitating the body after AFM is rare, but Bodo and the family have worked tirelessly to help Lorelei regain as much of her former strength as possible.
“My daughter Lorelei got a rare illness, a viral infection was causing swelling on her spine and brain,” Bodo writes. “Over the course of a few hours, she turned from being the cheeky, playful girl she has always been, to a girl who was struggling to breathe, and whose body was being paralyzed. By the time I got to her in the hospital she had lost the use of her left arm, her core muscles were seriously weakened, she could not walk, stand, or sit, and struggled to breathe and speak.”
Bodo, a tech wizard, decided that one important way he could try to help young Lorelei was with a 3D printed prosthetic device for his daughter’s elbow. Incredibly, the dedicated father attracted interest in the project from all over the world, with experts from far and wide contributing knowledge and ideas for the device. (Bodo gave a talk about this unusual collaborative process at the recent Hackaday SuperConference.) Now, the wearable 3D printed prosthesis uses a myoelectric sensor system to detect weak signals from Lorelei’s bicep and tricep to control an actuator which moves her arm, helping her to relearn normal movement.
Creating a 3D printed prosthesis for Lorelei presented a big challenge for Bodo, and for many reasons: For one, the device had to remain incredibly light. Lorelei is, after all, only five years old, and her already weakened limb can only take the smallest amount of extra weight. Given this restriction, Bodo calculated that the prosthesis could only weigh a maximum of 150 grams. Secondly, the actuator of the device needed to be powerful enough to move Lorelei’s roughly 400 gram forearm, while around five hours of battery life was the minimum requirement for the device to be practical for everyday use.
Although Bodo had no experience of making prosthetic devices, he had a partner helping him along the way: Lorelei herself. The keen youngster helped her father research similar projects online in order to find out how people were taking muscle signals and using them to move things. Help was also provided by strangers, some of whom assisted in the 3D scanning of Lorelei’s arm to ascertain the shape and dimensions of the problematic limb. Later, a company from Canada provided a number of actuators for the prototype.
“After a few weeks, we had a pretty good understanding of all the components we needed to get something working,” Bodo recalls. “With a tight budget, we went shopping... we bought an Arduino, an EKG board, various sensors and built an arm rig to test it all out on.”
Early versions of Lorelei’s 3D printed elbow had their problems. When Bodo and Lorelei tested out the EMG sensors on one early prototype, they discovered that the muscle signals from the youngster’s damaged arm were almost completely lost in the noise. Because of this, the father-and-daughter duo implemented a clever seventeen-sensor method, provided by another helpful company, that uses machine learning to find those signals. This process has even been turned into a video game of sorts, with Lorelei able to move her arm while watching a digital representation of the movements on a television screen.
The newest version of the 3D printed prosthetic device was assembled with the help of Fischer Technik, an educational toy company from Germany, which demonstrates just how much interest Lorelei’s story was able to generate in the online community. Once the design was finalized, the family duo then 3D printed a lattice out of PLA that had been precisely modeled on the 3D scan of Lorelei’s arm. This lattice was printed flat, before being submerged in boiling water to soften it, then molded to a full-size cast of the arm.
Amazingly, some rehabilitative progress has already been made using the 3D printed arm device—this despite the rarity of AFM sufferers ever regaining their original bodily capabilities in affected areas. Perhaps just as amazing, however, has been the huge wave of support—both technical and motivational—from people all over the world who have been following the Hoenens’ project. Lorelei’s progress goes to show just how much can be achieved when everybody pitches in to help.