Prostheses that replace lost fingers are typically complex, expensive devices, the cost of which often isn't covered by medical insurance. The student-designed Lunet, on the other hand (no pun intended) is simple and can be made from open-source plans.
David Edquilang came up with the idea when he was still an undergraduate student at the University of Houston's Gerald D. Hines College of Architecture and Design. He and his mentor, Assoc. Prof. Jeff Feng, wanted to create a robust, economical, wearable aid for a woman who lost three of her fingers due to frostbite.
The resulting 3D-printed prosthesis (which won a 2023 Red Dot: Luminary award) is composed entirely of polylactic acid and thermoplastic polyurethane plastics.
It has five main components: a hand plate which goes over the back of the hand, a wristband that is used to hold the hand plate in place, and three fingers which pop into mounts on the plate – no adhesives or special tools are required to assemble the device.
Each of the fingers is made up of four articulating sections (connected to one another via plastic pins), along with an internal linkage bar that runs the length of the finger, from base to tip. This arrangement forms a crossed-four-bar-linkage-style mechanism that has been modified to include a fifth bar.
Each finger is also connected to one of the residual finger stumps via a ring at the bottom. As that stump is moved up and down by the user, its prosthetic finger correspondingly moves up and straightens out, or moves down and curls inward. In this way, the Lunet can be used to grasp and release objects.
And importantly, each finger can bend backwards a bit relative to the hand plate, allowing it to flex rather than break under pressure.
Edquilang tells us that a refined version of the plans for the Lunet will likely be available via his website by December. And yes, the device can be made with any number of fingers, as required by the recipient.
"I designed Lunet to be extremely flexible in its modularity and configurability," he says. "It can be configured to fit any amputee's anatomical dimensions and any combination of fingers they may have lost. It can be one to four fingers, regardless of which fingers they may be."
And should you be wondering, the word "lunet" refers to a small moon, which orbits a planet in the same way the Lunet's fingers partially orbit the user's residual finger joints.
Source: University of Houston
