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Prosthetic Arm

Easton LaChappelle shows off an earlier version of his robotic arm. [via Popular Science]

By Stett Holbrook, Make Magazine

When he was 14, Easton LaChappelle built a robotic hand because he thought it would be cool. He made the hand out of Lego bricks, fishing wire, surgical tubing for fingers, and five independently-controlled servos. The robo-hand won Easton third place at the Colorado state science fair in 2011, but he was unsatisfied with the robot’s functionality so he set about improving the design.

The second version of the hand grew into an arm and featured a combination of 3D printed parts, dental rubber bands for tendon-like spring action, nylon-coated jeweler’s wire for ligaments, a telemetric Nintendo Power Glove, and a brainwave-activated headset to control the arm’s movement. For muscle power, he made a servo by adding a potentiometer to a DC motor.

Easton’s inventions created a stir, both because he was so young, and because the devices were flat-out amazing. Oh, and when he started, he knew nothing about electronics or programming. He taught himself. Easton, who lives in the small town of Mancos, Colo. near the Four Corners area, got coverage in Popular Science, Popular Mechanics, and MAKE and won a 2nd place ribbon at the Intel International Science and Engineering Fair, the nation’s top science fair.

As impressive as the robotic arm was, Easton realized he wanted to create something that did more than clutch a can of soda. A girl at the Colorado science fair last year gave him the inspiration he needed.


A CAD rendering of Easton’s robotic arm.

The young girl was born without a right arm and wore an $80,000 prosthetic limb. She controlled the arm via a spinal implant. As a maker, Easton was impressed by the technology, but distressed to learn the girl would need new arms as she grew, a tremendous expense for the family.

“That kind of opened my eyes,” said Easton, now 17. “I thought I could turn (my invention) into a prosthetic arm and help a lot of people.”

His mission was to build a robotic arm that was as functional as it was affordable. He thinks he’s done it.

Version 3.0 of the robot uses a Teensy Arduino microcontroller as well as amplifier circuits and Bluetooth receivers. To control the arm, the user flexes a muscle to choose from a menu of movements then performs a series of eye blinks to select pre-loaded gestures such as hand, elbow, or wrist movements. Once a movement is selected, an EEG headset measure brainwaves to control the movement. Total cost for the device? $250.

Except for the gears, motors, and screws, all parts were 3D printed on a Printrbot. Easton counts Printrbot founder Brook Drumm as a key mentor.

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