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The Tuister is a device for navigating hierarchies, such as nested menus. It is a Tangible User Interface for two-handed interaction and provides input and output at the same time. It was developed jointly by the Fluidum and the REAL projects as a universal interaction device within the Saarland University Pervasive Instrumented Environment (SUPIE). Currently, a new version is being built in cooperation with the Embedded Interaction research group at the University of Munich. Funding is provided by Deutsche Forschungsgemeinschaft (DFG).
The Tuister consists of two similarly sized cylindrical parts on a common central axis. These two parts can be twisted against each other. The right part is called the head and contains a number of displays distributed around its curved nappe, for example six displays in a hexagonal arrangement (see Fig. on the right). The left part is called the handle and is only used for manipulation.
Turning the head of the Tuister provides a very intuitive way to choose
from several items on the various displays. The list of items can be
arbitrarily long as the user is winding an imaginary tape with the
device. Displays on the back side can be switched off and reappear with
different content, which allows for arbitrarily long lists. To make
faster progress, the head can be set in rotation and spin freely,
until the target item comes closer. Once the target item appears on the
primary display, it can be selected by rotating the handle with the
head held fixed. If
we think of hierarchical menus, the rotation of the handle can
metaphorically be read as fastening and unfastening a screw, which
intuitively translates into up and down movements in the hierarchy:
turning the handle clockwise selects the current item or goes to the
corresponding submenu, if there is one. Turning the handle 
counterclockwise unwinds from the menu to the menu above, if there is
one. Spinning the handle freely clockwise goes all the way down along
the default choices, spinning it counterclockwise goes all the way back
up to the root. If we think of twodimensional structures, such as
tables or maps, turning the head can move up and down, while turning
the handle can move left and right, again using the screw metaphor.
We envision the Tuister as a personal multi purpose device we carry with us to interact with the many pervasive environments we encounter. Discrete displays might be substituted by a continuous display foil. Tuisters might assume the size of a ball pen, be attached to our key chains, or become foldable to protect their display while we carry them in our pockets. They might serve as a universal remote control to our video and sound systems or simply contain a digital radio or MP3 player. They might be our keys to and handles for pervasive environments.
Above are some alternative, foldable designs for the Tuister (Copyright by Altmayer Design, Germany). They protect the displays when the device is carried and provide a ledge for holding and turning the head without touching the actual displays.
After several prototypes with different levels of functionality, our current prototype uses a variation of the SmartIts particle boards and is being built in cooperation with the Embedded Interaction research group. It is linked to the environment via a radio connection and can navigate arbitrary hierarchies provided in an XML-based format.