In many ways, the e-NABLE movement, a web-based network of volunteers, and the nonprofit Enable Community Foundation (ECF) have come to represent the face of 3D printing and its potential positive impact on the world. With thousands of volunteers creating prosthetic devices for people across 83 countries, the e-NABLE movement has been able to increase the affordability and accessibility of prosthetics and assistive devices through the use of low-cost 3D printers.
Moreover, even as the movement's prosthetics spread like wildfire around the globe, the actions of the e-NABLE network provide ongoing case studies in open design and distributed manufacturing. On the one hand, the ability to share CAD files and print them locally has allowed these prosthetics to get to those in need quickly and easily. On the other, the e-NABLE network has illuminated some of the hurdles that arise when disparate volunteers design very personal devices for people from diverse cultures and backgrounds.
3D-Printed Prosthetics in the Global Context
Those familiar with the Enable Community Foundation and the e-NABLE movement through popular media's coverage of its 3D-printed prosthetics may have already noticed that the most heavily publicized devices are partial hand prosthetics for children. While it’s clear that these devices serve an important social and emotional role for wearers, ECF has learned that their physical functionality is quite limited. Furthermore, the partial hand prosthetics created by the movement often serve only a small portion of the global population.
“Pretty much every single rigorous academic investigation of these devices, particularly the partial hand devices, has found that they achieve very low physical functionality,” Bastian said. “Most e-NABLE hands score poorly on these assessment tests. That being said, they’re not necessarily about traditional physical functionality. Their role is as a conversation starter, a social-emotional catalyst to change the conversation around limb differences.”
Upon receiving a $600,000 grant from Google.org and a $100,000 grant from the Autodesk Foundation, ECF decided to allocate these resources in the most effective way possible.
“What we learned from that design summit is that congenital pediatric partial-hand limb differences probably account for far less than one percent of the world’s population with limb differences,” Bastian said. “The global breakdown is that the majority is lower-limb differences, below or above the knee. Of the remaining 30 or 40 percent, the majority are transradial, between the wrists and elbow, or transhumeral, between the shoulder and the elbow.”
With this information, ECF recognized the need to expand internationally beyond North America and Europe, where most recipients of e-NABLE devices live. “Those kids often do have multiple existing healthcare options for securing a low-cost or free prosthetic device,” Bastian said. “Looking at what is the most impactful problem that we could solve, we rapidly began to see that the biggest problems are not domestic to the United States.”
What might look like a superhero or robot hand to an 8-year-old American child, however, raises completely different associations in Haiti. Bastian pointed out, “The cultural fit is probably one of the biggest factors. e-NABLE hands that are widely familiar to us via the media were actually greeted as zombie hands in Haiti. They actually triggered some very specific cultural associations with body integrity and with voodoo culture.”
Distributed Human-Centered Design
The benefits of 3D printing over traditional manufacturing include the ability to create personally tailored goods. Since the planet is teeming with more than seven billion unique individuals immersed in their own cultures and environments, though, the person who will be using the product must be taken into consideration, resulting in what Bastian called “distributed human-centered design.”
“The problems that make sense to solve with additive manufacturing often require highly contextual, highly localized design and a lot of conversations with the people you’re actually trying to impact in order to effectively create a solution. It's really important to understand that the devices that The Enable Community Foundation has made to date are not designed for users in very resource-constrained areas, in extreme poverty, in other cultures,” Bastian said.
According to Bastian, the guiding advice from prosthetists is that “a prosthetic device should be used to address the user's greatest perceived loss.” For a tennis player who has lost an arm, for instance, the goal might be to regain the ability to play tennis.
In the case of the Haitian population, the aesthetic and functional needs of recipients in developing countries are not the same as they are in the U.S. and Europe.“We found that, in Haiti, one of the biggest problems is a really systemic stigma against any sort of physical disability,” Bastian said. “This is a stigma that is strong enough that it prevents people with limb differences or other physical disabilities from catching public transit, makes it difficult to go out to the grocery store, participate in various community events and activities, go to weddings and attend church.”
Rather than design a prosthetic with physical functionality, ECF volunteers worked closely with Haitian prosthetists at a clinic in Port-au-Prince to design a passive, ultra-lightweight cosmetic device. There are no moving parts, but the prosthetic provides a pretty good match on skin tone and weighs only 260 g. Wearers can perform daily activities with less fear of being stigmatized. In this way, the prosthetic serves a key life-affirming function.
The Challenges of Designing 3D-Printed Prosthetics
As Bastian points out, there are countless obstacles to working with such a large number of volunteers around the world on a problem as technical and personal as designing and 3D-printing custom prosthetic devices. One of the biggest is matching the diverse CAD backgrounds of e-NABLE designers.
CAD software comes in two dominant varieties: solid-body modeling tools like SOLIDWORKS, CATIA and Fusion; and mesh-based modeling programs like ZBrush, Blender and Maya. Moving from one to another isn't easy and each type has its advantages and disadvantages. While mesh-based software can be used to sculpt organic shapes, solid-body modeling lends itself to modularity and the parametric design of physical objects.
“We've run into some pretty big hurdles, in that work done in the mesh-based space is very difficult to take into the solid space, whereas work done in the solid-based space is pretty easy to take back into the mesh-based space,” Bastian said. “Most familiar e-NABLE devices—with the exception of one of the earlier devices—have been done in mesh-based tools, especially Blender, which makes it difficult to collaborate or have modular development. It puts a cap on the level of design that our community is able to do.”
As a result, e-NABLE hand designs may not be easily modified to suit different hands and wearers. Because individual components can't be scaled to the measurements of a given person, hands are scaled linearly. According to Bastian, “That results in something that we call ‘Hulk hand syndrome,’ in which you have these little eight-year-old kids walking around with these massive plastic assemblies on their hands.”
The Solution
To tackle this problem, ECF is developing an online design tool called LimbForge, which allows designers to create custom prosthetics through parametrically controlled modules. The biggest issue with web-based parametric design tools is the bandwidth associated with handling data-intensive 3D models.
Instead of requiring users to change design parameters that then alter the geometry of a CAD model in a native CAD tool, LimbForge will rely on a library of models called up when these parameters are changed. Since the human anatomy is already well understood, ECF can work within a well-defined parameter space, allowing the design team to create a number of models that make up each component of the final design.
Bastian described it this way: “We've changed the architecture so that everything is precompiled up front, though you go through a customization workflow—move sliders, input measurements. What that does is it just fetches an STL file from a library somewhere. We can make these very multidimensional lookup tables across all of these parameters and sample different parameters at different resolutions, but present that in a way that is very user-friendly. You don't have to go into a powerful CAD tool like Fusion or SOLIDWORKS to make those very detailed adjustments.”
LimbForge is already being used in Haiti right now. “The forearm component of our transradial device, the Ebewelleda Arm, is highly configured, made with multiple measurements taken by prosthetists and input into our web-based tool. That serves them with the parametric geometry which they then print onsite and fit to the patient during a patient visit,” Bastian said.
Meanwhile, tools like LimbForge will allow e-NABLE volunteers to better-sized and better functioning assistive devices with consistent mechanical clearances, machine-specific design improvements, and further opportunities for customization and expression.
Over time, ECF is changing the way that design and fabrication of 3D-printed goods is performed. The model behind LimbForge and the approach to 3D printing prosthetics requires a unique style of design thinking. Rather than think of 3D-printed products as individual, discrete designs, it helps to think of them as part of a “field” or “continuous space.” This approach is likely to spread from 3D-printed prosthetics to design for additive manufacturing overall.
As Bastian put it, “We're at the bleeding edge of a new generation of product design, a new type of product architecture.”For more about ECF, visit the organization's website, or watch the video below: