Shortcut – The Digital Prosthesis
People with prostheses are limited in their use of digital hardware: mouse, keyboard and touchscreen are not built to match their needs. However, amputees are often able to simulate movements with muscle control in their phantom limbs. Possibilities arise by creating a link between arm musculature and digital elements. Shortcut is a bracelet that combines phantom limb movement with an optical sensor creating contactless computer controlling. For example, tapping of the thumb and fore/middle finger causes a left or right click, and snapping closes the active window. This offers greater freedom in the workplace and beyond.
We are receiving funding from the EXIST scholarship program of BMWi and ESF and we’re alumnis of the DesignFarmBerlin Accelerator program. Shortcut was awarded the STARTS prize by Ars Electronica and the Mart Stam Förderpreis.
The design is mainly based on a repertoire of gestures that most amputees can still address neurologically. These were mapped to the most relevant computer in a sensible way. We have developed a catalogue of gestures that includes both basic functions such as cursor movement, left- and right-click and scroll, as well as quick access to functions such as zoom and quit. Thanks to a user-centered design approach the controls can be learned quickly and intuitively.
Its main body consists of two injection moulded interlocking parts that are rotatable. To activate the sensor, the upper part is rotated counterclockwise and locks into place, while the opening thus slides over the sensor.
The silicone wristband itself is detachable allowing for combinations with a variety of different bands. These include different circumferences as well as different colours and potentially materials to match user needs and individual taste.
Five people per week loose a hand in Germany alone on average. About 25% of these happen while working with heavy machinery. Myoelectric prostheses are the most common form of artificial hand replacement. Electrodes are inserted in the shaft of the prosthesis which read muscle signals in the stump of the arm. Motors in the hand and wrist can translate these signals into mechanical movements. For this functionality users need to learn how to use flexor/extensor gestures in different combinations to operate the system. Bending the Phantom Hand upwards opens the fingers of the prosthesis, bending it downwards closes them. By co-contraction, i.e. by clenching a fist, it switches into rotating mode, where the same bending gestures from before now trigger the two directions of rotation. The functions are connected in series, the gestures are used twice. Therefore the two types of movements cannot be carried out simultaneously.
Many people that were formerly doing manual labour have to be retrained, so that the number of those working in office jobs increases by six times after the amputation. And although this is the biggest group, the percentage of people using their prosthesis during work is alarmingly low. A major problem is working with desktop computers. When it comes to operating these, the prosthesis itself is practically useless because it lacks the fine motor skills and the tactile feedback required. In most cases this means that all operations have to be adapted to using only one hand, which moreover will statistically be the weak hand of the user. It takes considerable time and effort to learn and besides things simply take much longer than before. This complicates daily work considerably.