Input Equals Output. In a GUI, input devices are distinct and separable from output devices: a mouse is not a display. However, this separation is typically not true for interactions with physical objects. Paper documents may be stacked, moved around, and folded with a kind of physical immersion that can only be dreamed of in GUI windows. This immersion can only be achieved through a complete synergy between multi-finger, two-handed manipulations and corresponding visual, haptic, and auditory representations. This means displays should sense their own shape as input, as well as all other forces acting upon them. In an OUI, such input is not distinguishable from its graphic output: users literally touch and deform the graphics on display. As such, OUI displays render as a real-world object, into the shape that best supports data interpretation. Bits and pieces of such behavior are already found in Apple’s rigid planar iPhone display: its multi-touch screen, for example, senses the deceleration of the finger, providing an impulse to the physics engine to scroll the menu as if it was flicked.

Function Equals Form. According to Lloyd Wright’s mentor, Sullivan, the shape of a building or object should be predicated on its intended function, not its precedent: “form follows function.” Bauhaus popularized his credo by abolishing embellishments in everyday design. Lloyd Wright thought this was a mistake: according to him, form should not follow function: “they should be one, joined in a spiritual union.” This notion resonates with Gibson’s ecological approach to visual perception, embodied in the concept of affordance: the qualities of an object that allows a person to perceive what action to take. That is, the form of an object determines what we can do with it.

This describes well what Organic User Interfaces excel at: the physical representation of activities. Picking up a display activates it for input. Rotating it changes view from landscape to portrait. Likewise, bending the top right corner of the display inward may invoke a paging down action, while bending it outward pages up. Bending both sides inward causes content to zoom in, while bending outward zooms out. An example of such behaviors is found in Parkes’ Senspectra, a molecular modeling toolkit (see Figure 3). When a user bends the molecular model, LEDs embedded in the nodes glow according to the amount of strain exerted upon the optical fibers that connect them.

Form Follows Flow. Today, more than ever, meaning is appropriated by context. Similarly, OUIs adapt their form to better suit different contexts of use. Their shape fluidly follows the flow of user activities in a manifold of physical and social contexts of reuse, as well. A simple example is found in the use of folding in clamshell cellphones. Opening the clamshell activates the phone, a very strong affordance indeed. Closing it ends its functionality, deactivating the keys, protecting the display and reducing its footprint, all in one movement. A more profound example is found in the Readius: its display folds out when needed, thus doubling the available screen real estate when the activity such requires. Like clothing, forms should always suit the activity. Clothing fits the body while closely following its movements, and can even be deformed to serve other functions, like holding objects, if necessary. Thus, if the activity changes, so should the form. This kind of adaptation is best exemplified by actuated OUIs like Lumen [ 6], a display that changes shape in 3D, or by SensOrg, an electronic musical instrument with a flexible arrangement of inputs that are molded to varying physical or creative demands [ 10]. The Moldable Mouse in Figure 2b shows how malleability also reduces the risk of painful repetitive strain injuries. Its body—made of non-toxic polyurethane-coated modeling clay with stick-on buttons—allows input to literally follow the shape of the hands.

 

EARLY EXAMPLES OF ORGANIC USER INTERFACES One of the first systems to exhibit OUI properties was the Illuminating Clay project [ 5]. Bridging the gap between TUI and OUI, it was the first interactive display made entirely out of clay. With their hands, users could deform the clay model, the topography of which was tracked by an overhead