How Far Have 3D-Printed Prosthetics Come and Gone in the Last Five Years?

The current state of function and form in 3D-printed prosthetics.

According to recent estimates by the World Health Organization (WHO), 40 million people need prosthetic and orthotic devices. Yet only 5 to 15 percent of those 40 million people have access to them. This means that 34 to 38 million people are without prosthetic and orthotic devices. The people who need access to these devices reside largely in rural areas of developing countries. Even those who live in urban areas of developing countries only sometimes have access to healthcare centers. But those in need of prosthetics in rural areas must suffer the inconvenience and cost of expensive trips to cities to receive treatment.

It turns out that access to prosthetics is particularly difficult for amputees due to the scarcity of treatment centers, trained professionals and materials. The hackerspaces we take for granted in the developed world that provide 3D printing workshops are generally nonexistent in such places. There is no meetup to learn how to 3D print a multi-articulated prosthetic hand inexpensively.

Origin of the 3D-Printed Mechanical Hand

If you have followed 3D printing from 2012-2016, you might remember the story of open-source nonprofit E-NABLE. A designer named Ivan Owen built a functional puppet hand for a steampunk-themed costume and posted a video of his creation on YouTube. He was then contacted by a South African carpenter named Richard Van As, who suffered the accidental loss of his fingers while working on the job. As the two began to collaborate, Owen decided that 3D printing might make designing a hand for Van As more efficient. He shared the design with the open-source community, where it was free for anyone to use. E-NABLE was formed by an expanding group of people who were offering to 3D print the files and manufacture Owen’s mechanical hand.

Chapters of E-NABLE opened in different countries and like most open-source ideas, interesting mutations occurred. An E-NABLE group in Canada collects plastic waste and recycles it to transform it into sturdy filament to 3D print the prosthetic hand. There in an E-NABLE chapter in Yemen, which prints and assembles the hands for victims of Yemen’s ongoing civil war. You might remember the work of Christian Silva, who added distinct superhero elements to the prosthetic devices for kids. Iron Man himself (Downey Jr., not Musk) gave a 3D-printed Iron Man arm prosthetic (created by Albert Manero) to a child in 2016.

After E-NABLE set the tone for work in this area, many other organizations and companies have sprung up to practice and promulgate the concept of helping out those in need of prosthetics and orthotics.

Handicap International—France-based Handicap International started its mission to equip prosthetic limbs and arms to people in developing countries and those subjected to conflict and instability. Just a year after launching, the organization equipped 19 patients. (Image courtesy of Handicap International.)

Doctors Without Borders—The war in Syria has been a horror, and Doctors Without Borders (DWB) began a trial program to use 3D-printed prosthetic limbs for amputees who lost limbs in the ongoing conflict. At a hospital in Jordan, DWB was able to design and manufacture a prosthetic limb in 24 hours, reducing both the time and cost for a fraction of the resources needed to produce the devices via traditional methods. (Image courtesy of Doctors Without Borders.)

New Innovators

The 3D printing prosthetic movement has taken on a life of its own, extending beyond hands and arms to producing prosthetics for legs as well. Some new organizations and companies are addressing the psychological issues that can occur with patients using prosthetic arms and limbs. Addressing form more than function is important for wearers in the developed world, but improving function is still the moving target mechanical engineers and designers are aiming to hit.

Glaze Prosthetics—This company was founded in 2017 in Krakow, Poland, and gives a full range of stylistic options to patients, who can choose from different models and order them online. Glaze Prosthetics uses industrial additive manufacturing, specifically HP MultiJet Fusion technology. The company recently added new features and components, including a powerbank and embedded Bluetooth speaker. (Image courtesy of Glaze Prosthetics.)

Ayúdame3D—A remarkable industrial engineer named Guillermo Martinez began making 3D-printed prosthetics at the ripe old age of 24. Since he began his work, Martinez started his own company called Ayúdame3D, whose goal is simple: deliver as many prosthetic arms to citizens of developing countries who are in need of them for free. Since it began, the company has delivered 50 3D-printed prosthetic limbs all over the world. Ayúdame3D is expanding its production network to keep costs down while increasing output and the number of prosthetics delivered. (Image courtesy of Ayúdame3D.)

UK-based Open Bionics won a multimillion-dollar series a round of funding in 2019 and says that its multigrip bionic hand is now affordable enough to be covered by health insurance systems in developed nations in the West. The company launched its “Hero Arm” in May 2018, which now sells well in the UK, France and Spain. The arm can fit children 9 years old and up. Amputees using the bionic hands can switch finger speeds and motions. This allows them to pick up small objects or carry larger items when necessary. Open Bionics is planning to serve the United States market this year and into 2020. (Image courtesy of Open Bionics.)

Christophe Debard lost the lower part of his right leg at the age of 13. His experiences as a teenager of dealing with the reactions of friends and strangers alike led him to explore additive manufacturing as a way to design something that would intrigue people. The prosthetic pictured here was created with HP Multi Jet Fusion 3D printers. He recently created a startup called Print My Leg, which details open-source blueprints that anyone can use. Debard’s open-source blueprints emphasize creating stylistic elements that fit one’s personality. (Image courtesy of Print My Leg.)

A Group of Mechanical Engineers Tries a New Approach to Scale Efficiency and Deliver 3D-Printed Prosthetics

Form is ultimately a luxury for amputees in the developing world. Refining function and ease of use will help make 3D-printed prosthetics available to those who need them. Many of the current versions of 3D-printed prosthetics require post-processing steps for assembly by a trained professional. In the areas where they are most needed, trained professionals are a rarity.

To address this, a group of mechanical engineers at Delft University of Technology recently published a paper entitled  “Functional evaluation of a non-assembly 3D-printed hand prosthesis”, which addresses an interesting technical issue that slows down the proliferation of prosthetics to people in the developed world who need them.

A 3D-printed prosthetic needs to be properly fitted to the residual limb, but the amount of assembly steps can always be reduced. The team at Delft created a new approach to designing and 3D printing nonassembly active hand prostheses. They researched how to reduce post-processing steps to as close to zero as possible, thereby increasing the likelihood that the devices would be distributed to those in need.

Utilizing common fused deposition modeling (FDM) 3D printers (specifically Ultimaker), the mechanical engineers designed four fingers coupled to the palm by a single hinged joint, giving each finger degree-of-freedom rotation motion. Joined through a whippletree arrangement, the fingers move relative to the geometry of how a grasped object grabs an object with equal pinching force. Known as adaptive grasping, the total pinching force is distributed equally to each finger as it adjusts to the object being grasped. 

(Image courtesy of Delft University of Technology.)

When the fingers are in motion, they are animated by a force transmission scheme from a combination of three things: the main driving link, the links that connect each finger, and the whippletree arrangement. The hand is actuated and achieves linear motion by following the Bowden cable that is attached to the main driving link.

The hand opens via return forces generated by leaf springs, which are connected a tone end to the whippletree and at the other to the base of the fingers. This leaf spring configuration was designed through the development of 3D-printed plastic sheets, which work both as pulling mechanisms and elastic bending components. After the fingers are activated, pulling forces unbend the leaf springs, creating a straight configuration, which in turn creates a springing movement. This reduces actuation and return springing into one nonassembly 3D-printed element.

The only separate 3D-printed part aside from the prosthetic hand itself is a cover that encases the whippletree mechanism. This part forms the palm and is assembled easily with snap-fit joints. The circular cross-section of the fingers’ hinges are parallel to the build plate of the 3D printer, which allows the layers that form the leaf springs, driving link and whippletree mechanism to form perpendicular to the moving direction of the hand. This ensures that the hand’s mechanical properties will remain sound. 

Bottom Line

There are so many individuals and organizations involved in this effort to 3D print prosthetics, reducing the cost, increasing the quality of custom fittings, and creating new innovations for those in need all over the world. New approaches that emphasize customization and add stylistic elements are great for helping amputees overcome the psychological challenges they face, but ultimately improving function and ease of assembly like the work of mechanical engineers at Delft University of Technology will alleviate the most suffering of amputees in developing countries who do not yet have access to 3D-printed prosthetics.