With 3D printed limbs, the future is here

Designer Paul Sohi talks about creating prosthetics with digital technology - and the "insane engineering" behind giving the folks who need them a new lease of life

Paul Sohi doesn't really like to talk about himself. "I'm British," he laughs, by way of explanation. A Fusion 360 expert and product designer for Autodesk, the London-based creative recently put the finishing touches on a major project - namely, designing the world's first 3D printed performance prosthetic for paralympian cyclist Denise Schindler to use at the Rio Olympics later on this year.  
The finished product took a fraction of the time it would've taken conventional methods, cost "astronomically" less - and was even part of a discussion about the future of manufacturing with US President Barack Obama and German Chancellor Angela Merkel at the world's leading trade fair for industrial technology last month. Point to note: Paul is just 28.
When he'd first started out as a graduate architect, Paul worked at a few practices around the world and completed his masters, before deciding he "didn't want to draw toilets" for the rest of his life. His first foray into prosthetics was with the eNABLE group, an online community that uses 3D printing to design prosthetic limbs for children. "A lot of national health services in different countries are usually unwilling to give prosthetics to kids, because of how quickly they outgrow them," he explains.
The prosthetics would only last six to 12 months before the kids would get too big for them - but needing a new one so regularly obviously came with its constraints. Using 3D printing, however, the eNABLE group could make them quickly - and cheaply - thereby offering a practical solution to the need for regular replacements in children.
That "fledgling experience" was all Paul had before he signed up with Autodesk and the project with Denise, a silver medallist who'd lost her right leg in an accident at the age of two. "It was kind of like being pushed into the deep end of the pool," he laughs, but adds that it was a most welcome challenge. "To generate a performance-level prosthetic for Denise would usually take anywhere between five to 10 weeks," he explains. "Our goal was to see if we could improve the process with digital technology and build one that wasn't just quicker - but also better." And that's just what they did.
First, they scanned the stump and used it to build a socket from which to build the prosthetic. "It took all of 15 minutes to scan, followed by another four days to create the socket. In other words, we'd already shaved two weeks off the manufacturing time," says Paul. Next, they had to check the alignment of the leg - a process that would usually take a day or two, but something Paul could do in a "matter of minutes" by simply setting up a simulation to test the distribution of weight on the leg. Following which, all they had to do was 3D print it. The time difference from the conventional method of building prosthetics was tremendous. "We went from 10 weeks at their longest to three days at our longest. It's a real paradigm shift for the industry."

Paul Sohi
Seeing Denise ride with her new prosthetic for the first time was "indescribable joy", Paul recalls, with quiet elation. "For me, it was about designing an object but, for her, it's part of her body. She's incredibly passionate about cycling, so seeing her light up with the excitement of having a new leg and do her best to stretch the prosthetic to its limit is something I can hopefully repeat."
Perhaps the only other event that compared to that moment was when US President Obama and German Chancellor Merkel spent time with Denise at the Hannover Messe trade fair stand to discuss her story and the new prosthetic itself. "It's still not sunk in that that actually happened," says Paul, all smiles.
The toughest part of the project was learning all the "ins and outs" of prosthetic engineering, he says. "It's a melding of biology and engineering in a way that I've never experienced before." One such example was trying to find the right material to work with. Carbon fibre is commonly used in the making of prosthetics because it is both extremely light and extremely strong. "However, it's also a very rigid material - and that can cause a lot of friction in the socket when moving around, and therefore, a lot of discomfort for the wearer," Paul notes.
The team decided to use polycarbonate instead, which not only allowed them to create extremely rigid, strong parts to "transfer the power where Denise needed it" - but also create softer elements for flexibility and comfort. The end result weighed 812 gm as opposed to the 1.2 kg carbon fibre counterpart - a "pretty significant jump".
One of the key wonders of 3D printing is its incredible cost-effectiveness. "A performance level carbon fibre prosthetic would cost about 12,000 euros to build," says Paul. "It cost us US$200 to 3D print it; the metal parts were an additional $10 and an extra $5 for paint. The difference is astronomical! Even if you were to consider retail pricing, it would still cost significantly less."
Paul says he actually made two back-ups of the prosthetic he gave Denise - just because it was so cheap. Cheap, however, does not equate to poor quality in this case. The durability of the prosthetic is very much on point. "The chances of her breaking the first are extremely rare," he assures. "In fact, one of the stress tests we conducted was to bash a wooden table with the prosthetic - and we ended up denting the table. So, she'll definitely be using it for several years to come!"
Paul is equally optimistic of the future of prosthetics too. "I think we're going to see the use of bionics become a lot more widespread - as well as the integration of electronics. Think prosthetics that employ Segway-like stabilisation techniques, or being able to grip an object and feel it, as though the limb is an extension of yourself, instead of an addition... Apart from that, I can definitely see a future in body upgrades too. Imagine if I had fingers that split into 10 digits instead of five, I'd get so much more work done! I can absolutely see that happening in the next five years."
karen@khaleejtimes.com