05.16 3D Printed Prosthetics
3D Printed Prosthetics    


  • Amniotic band syndrome is a birth defect that affects development of limbs in utero
  • 3D printer technology can be used to create low-cost custom prosthetics for children born with limb differences
  • The e-NABLE community is an open source network of volunteers and patients around the world who work together to create upper limb prosthetics for patients in need.

Meet Isabella, a five-year-old girl sporting a pink plastic hand. “The hand has made Isabella into a confident young girl,” explains her mom, Cristina. Underneath the “robot arm,” as Isabella calls it, is a “little arm” with a partially developed hand and small fingers. Like most children, Isabella is great at adapting to her environment, and she has learned to function without full range of motion in the fingers and forearm of her right arm. Still, there are things that are harder to do without two full hands, like riding her tricycle and mini 4X4. The little arm also has been a target for other kids Isabella meets on the playground or at school who sometimes tease or bully her.


The little arm is the result of a congenital birth defect known as amniotic band syndrome or ABS for short. Researchers believe that ABS occurs when the inner membrane surrounding the fetus ruptures, releasing strands of the membrane, called amniotic bands, into the sac where the fetus is growing. The fetus can become entangled in the amniotic bands, cutting off circulation to limbs and causing developmental defects. There are approximately 1 in 1,200 to 15,000 babies born with birth defects caused by ABS in the United States. In extreme cases, ABS can also result in miscarriage or fetal death.

Traditional prosthetics do not always work for children with ABS, who each have a very unique limb difference.

When Isabella was in the womb, her forearm became trapped in amniotic bands, causing only partial development of her hand and fingers. In Isabella’s case, doctors said Isabella would need to have surgery to remove part of her underdeveloped arm in order to receive a traditional prosthetic. Isabella’s mom did not want to consider surgery as an option, and instead joined the e-NABLE community, an online network of designers, fabricators and researchers who make low-cost custom prosthetics for children born with limb differences. At the age of four years, Isabella began working with a team of designers at FATHOM, a 3D printing company in Oakland, CA to create a customized prosthetic.

Close up of the print head of FATHOM’s 3D Printer

New fabrication technology, like the 3D printer, has dramatically reduced the cost of prosthetics and has provided greater access to highly customizable prosthetics. The 3D printer is capable of producing three dimensional objects based on computer-generated designs. FATHOM specializes in 3D printing, which enables its designers to create highly customizable and functional objects at low cost. Using a 3D printer, the FATHOM team printed Isabella’s robot arm for approximately $50 worth of materials, provided to Isabella and her family at no cost.

At the beginning of the project, FATHOM Mechanical Engineer Bethany Casarez, Industrial Designer Ava DeCapri and Industrial Design Intern student Dylan Millsaps met Isabella to understand her goals for a prosthetic. The team experimented with existing designs for upper limb prosthetics that functioned either by movement from the wrist or from the elbow. None of these designs worked for Isabella. Wrist-activated prosthetics require sufficient wrist strength to maneuver the prosthetic hand. Elbow-activated devices work best when the forearm is missing. In Isabella’s case, she could move her wrist but did not have the wrist strength for the prosthetic to be functional. Isabella also has a forearm, so the elbow-activated device actually restricted her movement. After speaking with Isabella and her family, Casarez and her team determined they would need to develop a new design to meet Isabella’s needs.

The design that the FATHOM team created was an elbow-based design that was more minimal than the existing designs. The prosthetic attached at the elbow but did not restrict the range of motion of the forearm.

To better understand, let’s focus on hand mechanics for a moment. Hold your hands in front of you and make two fists. Now open the fists. Now close them again. If you have a fully functional hand, your fingers will straighten and then curl at roughly the same time.

On many prosthetic hands, though, this is not the case. This is because each finger is connected individually to the wrist by a thin plastic wire. In order to change hand shape, the line controlling each finger must be individually tightened or loosened. This design is time-consuming when initially assembling the prosthetic and when being used by the patient. To improve this design, Casarez and her team created a single attachment point on the wrist for all five fingers. In order to change hand shape, the patients simply have to turn a single knob on the prosthetic.

Now try to pick up an object in front of you: a pen, eraser or textbook. As you go to pick up the object, watch how your fingers wrap around it to form a grip. Do all of your fingers stop moving at the same time? Not unless you are picking up a perfectly cylindrical object right in front of you. Rather, your fingers will adjust to the size and shape of the object. This is known as an adjustable grip.

Many prosthetic hands, though, do not have an adjustable grip. As soon as the first finger touches the object to begin to pick it up, all of the other fingers stop moving too. To improve this design, Casarez and her team used a triangular device called a whippletree. The whippletree can rotate as the fingers curl to allow the fingers to close around the object independently. This design allows the patient to have a more natural gripping motion.

The single point finger attachment is one example of a design improvement added by the FATHOM team. When creating designs, though, the engineers must think about two groups of people at once. The patient, of course, because the goal is the best function for the patient. But the engineers must also create a design that can be easily printed by the 3D printer and then assembled for use. “The widespread availability of low-cost fabrication technologies poses a different set of design challenges,” Casarez explains, “I love exploring ways that 3D printing changes your approach to design.”

3D printed parts of Isabella’s robot arm

The FATHOM team used a Computer Aided Design program called Fusion 360 to create 3D models of their designs. The team then used 3D printers to build and test their designs. There are many types of 3D printers, which vary based on the materials used or the shapes of objects created. The 3D printer that the FATHOM team used is similar to a hot glue gun—it extrudes hot plastic out of a nozzle layer by layer, gradually building up the 3D dimensional object defined in the computer program.

The first time the engineers printed their design they could see immediately that it didn’t work right. “The plastic was too thin in some places,” recalls Casarez, “and some features didn’t work like we expected.” The engineers used this information to improve the design, adding thickness to the areas that had been too thin and trying out new mechanism ideas. After printing and re-testing many times, they achieved a prosthetic they thought might work for Isabella. But Isabella was the only one who would know for sure. Isabella made several trips to FATHOM to try on her new arm.

Although the prosthetic had worked well for the engineers in the laboratory, it was clear that Isabella was having difficulty when she first tried it on. The prosthetic was too heavy for her to manage and pinched her skin in certain places. Casarez and her team observed Isabella attempting to use the prosthetic and talked to her about her experience. They then used this information to return to the laboratory and improve their designs.

“It used to be that kids would tease Isabella about her hand. She would hide it and run away,” recalls her mother. “Now she is so proud to show off her robot hand. She is so confident.”

In addition to the functionality of the prosthetic, it is equally important for children that they accept how the prosthetic looks. Many older prosthetics have stocky boy-like fingers and dark colors. Isabella wanted her prosthetic to be bright pink. The plastics used for 3D printing come in many colors, and the engineers happily fulfilled Isabella’s request. “It used to be that kids would tease Isabella about her hand. She would hide it and run away,” recalls her mother. “Now she is so proud to show off her robot hand. She is so confident.”

Close up picture of Isabella’s 3-D printed robot arm by FATHOM

As she has grown, Isabella has also become more interested in how her prosthetic hand works. She will think about its design and how to make it better. “She may even grow up to be an engineer and design her own prosthetic hand,” jokes her mom.

Isabella is not alone. There are thousands of children and adults in the United States and around the world with congenital birth defects affecting mobility in their limbs. There are thousands more missing limbs or parts of limbs due to accidents, illness, or injury. Their lives could be improved by low-cost prosthetics like the one made for Isabella, fabricated using a 3D printer. This is how the e-NABLE community started.

The e-NABLE Story

Overview of e-NABLE

In 2011, artist and designer Ivan Owen from the U.S. posted a video on the internet of a surprisingly functional metallic puppet hand he created as part of a costume. The video was seen by a carpenter in South Africa named Richard Van As who had lost his fingers in a woodworking accident. Richard reached out to Ivan, and together, across continents, they used household materials to create functional fingers for Richard.

A South African mother of a five-year-old born without fingers heard about the project and contacted Richard and Ivan to ask about creating a miniature version of the hand for her son Liam. Ivan did some research—this was one of his favorite hobbies, after all—and created a prototype hand for Liam. Ivan soon realized, though, that, as a growing boy, Liam would quickly outgrow his prosthetic hand. In search of a solution, Ivan discovered 3D printers and taught himself to use them. He also contacted a 3D printer company that agreed to donate a printer for him to use. This is how Ivan in the United States created the first 3D printed mechanical hand for Liam in South Africa.

The story does not end there. Rather than keep the designs for himself, Ivan decided to release his creations into the public domain for others to use and improve upon. And others did!

In 2013, Dr. Jon Schull, Professor at the Rochester Institute of Technology in Rochester, NY, found a video about Liam and the 3D printed mechanical hand. Dr. Schull noticed that many people from around the world had left enthusiastic comments on the video suggesting they would be proud to do something like that too. Schull left a comment of his own suggesting they add pins to an online map he created, noting if they had a printer and wanted to help or if they knew someone who needed a hand. Within days, people started putting pins on the map, and to help the group self-organize, Schull created a Google Plus community connecting designers, 3D printers, and patients with each other. In just one year the group grew from 100 to 3,000 members who created 750 hands for people around the world. The second year saw membership increase to 7,000 members who built an additional 2,200 hands. And the group, known as e-NABLE, is still growing. In fact, this is how Casarez and her team at FATHOM found Isabella.

This is an amazing community to work with,” remarks Casarez. “The rate of innovation and collaboration is astounding and extremely rewarding.”

The initial designs for wrist- and elbow-activated prosthetics used by the FATHOM engineers came from the e-NABLE community, which urges that all designs and improvements remain open and available for public use. FATHOM’s improvements were given back to the e-NABLE community for others to use, improve upon and change. “This is an amazing community to work with,” remarks Casarez. “The rate of innovation and collaboration is astounding and extremely rewarding.”

Although many professional engineers are involved in the e-NABLE community, it is not a professional group. Everyone is a volunteer and anyone interested in the project can get involved in some capacity, including middle and high school students. Educators initially became involved with e-NABLE because science teachers were looking for projects that could be done using 3D printers available at their schools.

One such educator is Rich Lehrer, an 8th grade science teacher in Manchester-by-the-Sea, MA. Lehrer was already doing design work with students on Science Technology Engineering and Mathematics (STEM) education through a partnership with Massachusetts Institute of Technology’s D-Lab. He began working with 3D prosthetics when his son Max, who was born without fingers, was 3 years old. “That’s when this type of authentic STEM and problem based learning work with students took on a whole new meaning for me,” Lehrer recalls.

When Max was 3 years old my students were one of the first school groups – in 2013 - to print and build one of the original Robohands for a recipient. Lehrer’s students went on to use 3D printing to build a mechanical hand with that could be used by Lehrer’s son. “And I’m always thinking of ways to improve the design,” says Lehrer. For example, there is now an adaptor system that allows kids to design “purpose specific” attachments for the hands. “The photo below shows an example of one such attachment (the blue part) that a 6th grade student designed last week for Max, which now allows him to hold a drum stick in his right hand,” Lehrer adds.

The blue part pictured above is an attachment designed by a student to attach to the 3D prosthetic hand to allow the wearer to play the drums.

Lehrer is now the E3STEAM (Enable Education Exchange) Coordinator for the Enable Community Foundation worldwide. He helps schools develop their own projects, often working with patients and families in need because some schools do not have close school/recipient relationships. “The possibilities are endless,” Lehrer continues. “We are always looking to get more people on board.”

Casarez and her team at FATHOM are now working with an 11-year-old boy to help him create his own prosthetic in partnership with a nonprofit organization called KIDmob. “I am honored to be part of the e-NABLE and KIDmob communities,” Casarez concludes. “I am really looking forward to our next project.”

Bethany Casarez is a Mechanical Engineer at FATHOM, a 3D printing company headquartered in Oakland, CA. She is one of the Project Leaders for the FATHOM collaborations with e-NABLE and KIDmob. When not working, Casarez enjoys using 3D printers to create jewelry and other objects out of natural materials. She also makes pottery, paints, crochets and cooks.

Richard Lehrer is an 8th grade science teacher in Manchester-by-the-Sea, MA. He is also the E3STEAM Coordinator for e-NABLE helping to connect schools and students with patients in need around the world. When not teaching, e-NABLE-ing, or creating his own mechanical hands, Lehrer can be found spending time with his family and teaching teachers how to use Project Based Learning with the Buck Institute for Education.

The e-NABLE community is an open source network of volunteers and patients around the world who work together to create upper limb prosthetics for patients in need. The possibilities are endless. You can find out more about the community and how you can participate at EnableCommunityFoundation.org.

For More Information:

  1. Helping Hand: 3-D Printing for Isabella. http://studiofathom.com/prosthetic/
  2. 3-D Printing: Isabella’s Hand. http://3dprintinghome.net/3d-printing-a-helping-hand-isabellas-story/
  3. How to Make the Isabella Arm by FATHOM. http://www.instructables.com/id/E-NABLE-How-to-assemble-the-Isabella-Arm-by-FATHOM/
  4. E-NABLE. https://plus.google.com/u/0/communities/102497715636887179986
  5. E-NABLE Community Foundation. http://www.enablecommunityfoundation.org/about/
  6. E-NABLE Educators Exchange. http://www.enablecommunityfoundation.org/get-involved/build-a-hand/e3steam/
  7. Brookwood Students Reach Across the Sea. http://www.bostonglobe.com/metro/regionals/north/2016/02/19/from-manchester-sea-hands-across-sea/KRQY03AsGj7ub6IP7xbaQN/story.html

To Learn More:

  1. Rochester Institute of Technology’s Jon Schull Launches Revolution. http://www.democratandchronicle.com/story/money/business/2014/10/30/lahman-rits-jon-schull-launches-revolution/18138009/
  2. Birth defects. https://www.nlm.nih.gov/medlineplus/birthdefects.html
  3. E-NABLE Community Foundation in social media:
    1. Facebook: https://www.facebook.com/ECF2015/?fref=ts
    2. Twitter: https://twitter.com/Enablehands_ECF

Upper Limb Defects

3-D Printing


Written by Rebecca Kranz with Andrea Gwosdow, PhD at www.gwosdow.com


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Isabella with her pink robot arm and the FATHOM team from left to right: Bethany Casarez, Dylan Millsaps and Ava DeCapri

John Schull

Rich Lehrer

Fathom 3D Printing Video

Fathom 3D Printing Video

Rich Lehrer with his son Max and his former student Wesley D’Alelio, who built the hand that Max is using.

Video of Rich Lehrer and school project for his son, Max

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