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3D printable prostheses could restore amputees’ finger mobility



An easy-to-use 3D printable finger prosthesis created by a recent US university graduate could offer amputees a low-cost solution to restore finger functionality.

David Edquilang first designed Lunet, which doesn’t need metal fasteners, adhesives or special tools to assemble, as an undergraduate student at the University of Houston Gerald D. Hines College of Architecture and Design.

While standard prostheses can cost thousands of dollars, the researcher aims to make his design open access on the internet, instead of selling it.

Edquilang said:

“Not every good idea needs to be turned into a business. Sometimes, the best ideas just need to be put out there.

Medical insurance will often not cover the cost of a finger prosthesis, since it is not considered vital enough compared to an arm or leg.

“Making Lunet available online for free will allow it to help the greatest number of people.”

Edquilang’s mentor at the university was Associate Professor Jeff Feng, co-director of UH’s Industrial Design program.

Via a partnership with Harris Health System, Feng learned of a patient who had her fingers amputated due to frostbite.

Inspired by working on an upper limb prosthesis, Edquilang created prosthetic fingers that returned mobility to the patient, allowing her to pick up objects again.

He said: “It feels great knowing you have the capability to positively impact people’s lives and give them help they otherwise wouldn’t be able to get.”

Months later, the researcher was laser focused to make an even better product.

Over the course of two weeks, under Feng’s advisory, Edquilang designed and tested 60 prototypes before reaching a final design that was more durable, easier to configure and assemble, and had improved functionality.

His “breakthrough” came after a literal break in his design.

The researcher intentionally broke one of his prototypes to see where its structural weak point was.

It buckled at the distal knuckle, the joint that connects the bones at the fingertips, so Edquilang added a linkage that replaced the previously rigid distal knuckle, and an award-winning version of Lunet was born.

Lunet is made up of two common types of 3D-printed plastics: polylactic acid and thermoplastic polyurethane.

Each finger is comprised of four parts held together by plastic pins.

Edquilang describes arcs and circular orbits as the foundation for the motion of the finger mechanism.

Meanwhile,  geometric basis of the design evoked the idea that the prosthesis orbits around the user’s joints like a moon, or lunet, hence the name.

Another element of the device’s uniqueness is that it is nearly impossible to break; other finger prosthetics can be complicated and require many parts.

Edquilang said: “The problem with higher mechanical complexity is that these designs are less durable.

“The more parts you have, the more points of failure.

“You need to make prosthetic fingers robust and as strong as possible, so it doesn’t break under normal use, yet you want the design to be simple.

“This was one of the greatest challenges in making Lunet.”

The researcher has encouraged other design students not to be afraid to experiment and fail because that is often how one can learn to improve the most.

He said: “Where the world has an abundance of problems, designers have an abundance of talent, and we should not be selfish with it.”

Image: University of Houston

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