Curling prosthesis gives wearer tentacle reach

Industrial design students at the University of Washington imagine some intriguing upper-limb prosthetics, including one that adjusts its degree of curl depending on what the user wants to grab.

prosthetic arm
Kaylene Kau

Prosthetic limbs have come a long way in recent years, evolving from simple devices to complex, customized machines that respond to sensors and possess multiple degrees of motion, among other advancements.

Might high-tech tentacles be next? That's the vision of Kaylene Kau, a 2010 graduate of the University of Washington's Industrial Design Program who conceived of a motorized curling prosthetic arm as part of a senior project aimed at pushing the boundaries of current upper-limb prosthetic design.

The idea is that users of her prosthetic would be able to push a button to wind or unwind the cables inside the false limb and thus control the amount of curl depending on the task. Odd-looking, to be sure, but not unusually so amid the students' other futuristic-looking designs.

The prosthetic project was inspired by Joanne Tilley, whose arm was amputated below the left elbow and who is also a friend of University of Washington design professor Magnus Feil. Feil challenged his students to design an alternative to Tilley's prosthetic, essentially a crude hook attached to a plastic base, that were affordable yet stylish enough that wearers wouldn't be embarrassed to wear them. "He really went out of his way to push this project and mentor us," Kau told CNET.

With Tilley serving as an adviser, the students spent 10 weeks designing and testing their concepts, sometimes going whole days with one hand taped tightly to get a sense of the challenges faced by amputees. One notable finding, Feil said, was that the free hand could execute more complex maneuvers while the taped hand could manage simpler tasks, such as bracing an object against a counter while the dominant hand unwrapped it.

Kau's arm is shaped to adapt is curl to a variety of objects. Kaylene Kau

"That was an important discovery--that it doesn't always make sense to recreate a hand or fingers," Feil said. "It's more important to look at the interaction between the working hand and the prosthesis so the two can be team players. By finding these interaction patterns, students had lots of clues for their final designs."

The resulting prosthetics include an arm with a neoprene base to take weight off the natural arm and a slider function that opens and closes slowly enough to give the wearer time to clamp it to something. Another prototype features a "thumb" that flips down when the wearer needs to hold objects securely, while another prosthetic's shaped like a cradle that can hold small objects within the arm itself.

prosthetic arm
Sophie Milliotte's arm, designed specifically for women, has 90-degree wrist rotation and a sliding arm rest to gain leverage. Sophie Milliotte
prosthetic arm
The curved form in Kyota Hinami's arm holds small objects within itself, and has an additional hook and claw for better grip. Kyoka Hinami

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