Weight-Shifting Mobiles: Motion and Tilt in One-Dimensional Gravitational Displays

In this paper, we propose motion and tilt as an input technique for Weight-Shifting Mobiles, a recently proposed mobile interactive system that employs a moving center of gravity as an output channel. We present a prototype that combines weight actuation with accelerometer input. We discuss how motion- and tilt-based applications in current mobile devices can be enhanced through weight actuation, and, on the other hand, how weight-based output can be augmented through motion and tilt input. Furthermore, we point to new application spaces that arise from the proposed combination. We present a study in which we compared a button-based input technique and the proposed accelerometer-based input style for a weight-actuated system. We present three application scenarios: A supportive technique for graphical user interfaces, a gesture support scenario, and a balance actuation system. While the conducted user study did not reveal any quantitative differences in button- and accelerometer-based input, user comments indicate that motion and tilt are suitable, and in some cases even preferable, as an intuitive input for weight-based mobile interactions.