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A Wristband For Prosthetic Hands Lets Amputees Swipe, Click, And Zoom

The typical language of human-computer interaction falls short for amputees. Three design students think they have a solution.

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The vast majority of digital interfaces, from touch screens to keyboards and mouses, are built to be operated by two organic hands. So for amputees, the lack of fine motor skills and tactile feedback in current prosthesis technology can be a barrier to working quickly and efficiently on computers.

Enter Shortcut, a wearable that recently received the 2016 STARTS Prize, presented by the European Commission and Ars Electronica. Shortcut is designed to make prosthetic hands more facile when working with digital technology, taking simple hand gestures that most amputees can still trigger and mapping them onto the most basic, and necessary, computer commands—moving the cursor, left and right clicking, and scrolling.

Shortcut's designers—David Kaltenbach, Lucas Rex, and Maximilian Mahal—found that in their home country of Germany alone, an average of 15 people per day lose a hand, most of them to heavy machinery. "After they’ve lost the hand, many have to be retrained to be an office worker," says Rex. "They really have to deal with desktop computers and laptops all the time. It’s crucial for their work life and their personal life."

Amputees still send signals for hand movements through the muscles that remain in the arm of the hand they lost, an effect called the "phantom hand." One of the most common prosthetic technologies, called myoelectric prostheses, captures these signals using electrodes that sit on the end of the arm and uses them to direct movement in the prosthetic.

Shortcut builds on this same idea, but instead of requiring the fine motor skills necessary to operate a computer, the wearable reads those signals and translates them into basic gestures like touching your thumb to your pointer finger (for clicking), clenching your fist (for zooming in and out), and flicking your fingers up and down (for scrolling) for navigation.

To don Shortcut, users put it on by pulling the strap around the body of the device, a simple movement that makes it easy to attach to a prosthetic with one hand. To turn it on, users twist the body of the device once to uncover the optic sensor. The wearable sits on the wrist and contains a small circuitboard, an optic sensor, Bluetooth, and a battery. The Bluetooth connects wirelessly to the user's computer, and the optic sensor—the same technology used in a mouse—processes the movements of the hand.

While brainstorming, the three designers considered many different ways of controlling a computer interface—like moving your foot or waving your arm in the air—but landed on a simpler method of control. "When you want to move a cursor, it’s 2D motion, that’s what you’re used to," Rex says. "Then it was clear that the optical sensor has to be on the table." In the current prototype of Shortcut, amputees can simply put their prosthetic on a table and move it around in order to manipulate the cursor.

Aesthetically, Shortcut looks similar to a watch or bracelet. This was intentional—Rex said they designed it to look like a contemporary wearable rather than like a medical device. The wristband itself is detachable to save on potential manufacturing costs, and allow for customization.

The designers currently attend the Weißensee Academy of Art in Berlin, and developed the project in partnership with the fabrication studio Fab Lab Berlin and Ottobock, a German prosthetics company. While still in school, they hope to start working on a new prototype, begin user testing, and find investors to bring Shortcut to life. You can see Shortcut on display at the Ars Electronica festival in Austria between September 8-12.

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