Finger amputee shares 3D printed partial finger replacement device 'Knick Finger'

May 3, 2016 | By Benedict

Nick Brookins, a media services engineer at Akamai Technologies, has designed a 3D printable partial finger prosthesis called the “Knick Finger”. Brookins, whose design was recently shared by eNABLE, lost his own finger in 2014 after a motorcycle accident.

3D printed prosthesis specialist eNABLE is best known for designing, sharing, and distributing its own 3D printed prosthesic hand, a design based on the centuries-old Corporal Coles hand, but the nonprofit organization is gradually broadening its horizons beyond that design. Now a large international community, eNABLE is using its growing reputation to promote new 3D printed innovations for the limb different community, the most recent example being the Knick Finger, a partial finger replacement device designed by engineer Nick Brookins over the last two years as a solution to his own finger amputation.

The story of the Knick Finger goes back to the moment Brookins found himself in hospital in 2014 after a motorcycle accident. The severity of the crash required Brookins to have his right index finger amputated, but the engineer reacted to the setback with optimism and steely determination. Being a self-proclaimed “tinkerer”, the amputee began thinking about designing and 3D printing his own prosthesis before he had even left the hospital.

After dismissing the “silly silicone contraptions” offered to him by doctors, Brookins fired up 3D design software OpenSCAD and began work on his own device, taking inspiration from the Owen Replacement Finger, another 3D printed prosthetic device shared by eNABLE in 2013. When Brookins had added the finishing touches to version 1.0 of the Knick Finger, a “mashup” of the Owen Finger and the Flexy Hand, he printed it off on a Printrbot Simple 3D printer, before sharing the design online under a Creative Commons license.

The Knick Finger 1.0 was relatively successful, but Brookins was unhappy with various elements of the design, prompting him to start over—this time using 3D modeling software SketchUp. The Knick Finger 2.0, however, turned out to be more difficult to print and build than the first version, as well as being harder to tailor to individual hands. Brookins attempted another design, version 3.0, before finally getting it right with version 3.5, which can be assembled in about 30 minutes.

“I am super happy with version 3.5,” Brookins said. “It’s been easy enough to build that I can build a fun collection of different variations and I’m seeing that others are having more success with building their own. I think my device benefits greatly from me being both the designer and the consumer as I am able to address a lot of the little annoyances that would be hard for a designer that didn’t wear one to understand.”

Brookins uses the Knick Finger himself, putting it on first thing in the morning and only removing it before bed. Wearing the device out and about has brought a number of inquisitive glances and conversations, with many observers mistaking the prosthesis for a finger brace. The designer hopes to share his design with as many finger amputees as possible, and has even been able to rework the design into a prosthetic thumb.

The 3D printable Knick Finger is available to download for free via Thingiverse. Brookins recommends printing at the finest possible resolution, with supports and an infill of 80%. PLA is recommended for the knuckles, middle section, and linkage, while a flexible material such as elastic TPU is best for the socket, tip cover, hinge plugs, and bumper.

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Posted in 3D Printing Application

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