ABSTRACT Flexible Physical Interfaces

Human-computer interface devices are rigid, and afford little or no opportunity for end-user adaptation. This thesis proposes that valuable new interaction possibilities can be generated through the development of user interface hardware that is increas-ingly flexible, and allows end-users to physically shape, construct and modify physical interfaces for interactive systems. The work is centred around the development of a novel platform for flexible user in-terfaces (called VoodooIO) that allows end-users to compose and adapt physical control structures in a manner that is both versatile and simple to use. VoodooIO has two main physical elements: a pliable material (called the substrate), and a set of physical user interface controls, which can be arranged on the surface of the substrate. The sub-strate can be shaped, applied to existing surfaces, attached to objects and placed on walls and furniture to designate interface areas on which users can spatially lay out controls. From a technical perspective, the design of VoodooIO is based on a novel architec-ture for user interfaces as networks of controls, where each control is implemented as a network node with physical input and output capabilities. The architecture overcomes the inflexibility that is usually imposed by hard-wired circuitry in traditional interface devices, by enabling individual control elements that can be connected and disconnec-ted ad hoc from a shared network bus. The architecture includes support for a wide and extensible range of control types; fast control identification and presence detec-tion, and an application-level interface that abstracts from low level implementation details and network management processes. The concrete contributions to the field of human-computer interaction include a motivation for the development of flexible physical interfaces, a fully working example of such a technology, and insights gathered from its application and study. ii