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We describe input devices and two-handed interaction techniques to support map navigation tasks. We discuss several design variations and user testing of two-handed navigation techniques, including puck and stylus input on a Wacom tablet, as well as a novel design incorporating a touchpad (for the nonpreferred hand) and a mouse (for the preferred hand). To support the latter technique, we introduce a new input device, the TouchMouse, which is a standard mouse augmented with a pair of one-bit touch sensors, one for the palm and one for the index finger. Finally, we propose several enhancements to Buxton's three-state model of graphical input and extend this model to encompass two-handed input transactions as well.

We report on the precise placement of a single carbon nanotube ͑CNT͒ onto a microlectromechanial system ͑MEMS͒ structure. Using a hybrid atomic force microscope/scanning electron microscope ͑AFM/SEM͒ system, an individual multiwalled CNT was retrieved from a cartridge by the AFM tip, translated to a MEMS device, and then placed across a gap between an actuating and a stationary structure. Progress toward a resistance versus stress/strain measurement on a CNT will be discussed, including SEM images of a MEMS structure we have designed specifically for such a measurement.

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We can touch things, and our senses tell us when our hands are touching something. But most computer input devices cannot detect when the user touches or releases the device or some portion of the device. Thus, adding touch sensors to input devices offers many possibilities for novel interaction techniques. We demonstrate the TouchTrackball and the Scrolling TouchMouse, which use unobtrusive capacitance sensors to detect contact from the user's hand without requiring pressure or mechanical actuation of a switch. We further demonstrate how the capabilities of these devices can be matched to an implicit interaction technique, the On-Demand Interface, which uses the passive information captured by touch sensors to fade in or fade out portions of a display depending on what the user is doing; a second technique uses explicit, intentional interaction with touch sensors for enhanced scrolling. We present our new devices in the context of a simple taxonomy of tactile input technologies. Finally, we discuss the properties of touch-sensing as an input channel in general.

Building on Buxton's foreground/background model, we discuss the importance of explicitly considering both foreground interaction and background interaction, as well as transitions between foreground and background, in the design and implementation of sensing techniques for sensor-enhanced mobile devices. Our view is that the foreground concerns deliberate user activity where the user is attending to the device, while the background is the realm of inattention or split attention, using naturally occurring user activity as an input that allows the device to infer or anticipate user needs. The five questions for sensing systems of Bellotti et al. [2002] proposed as a framework for this special issue, primarily address the foreground, but neglect critical issues with background sensing. To support our perspective, we discuss a variety of foreground and background sensing techniques that we have implemented for sensor-enhanced mobile devices, such as powering on the device when the user picks it up, sensing when the user is holding the device to his ear, automatically switching between portrait and landscape display orientations depending on how the user is holding the device, and scrolling the display using tilt. We also contribute system architecture issues, such as using the foreground/background model to handle cross-talk between multiple sensor-based interaction techniques, and theoretical perspectives, such as a classification of recognition errors based on explicitly considering transitions between the foreground and background. Based on our experiences, we propose design issues and lessons learned for foreground/background sensing systems.

BACKGROUND -SCRATCH DRIVE ACTUATORSThis paper presents a micro-actuator that operates free of any physically restraining tethers. We show how capacitive coupling can be used to deliver power to MEMS devices, independently of the position and orientation of those devices. Then, we provide a simple mechanical release process for detaching MEMS devices from the fabrication substrate once chemical processing is complete.To produce these untethered micro-actuators in a hatchcompatible manner while leveraging existing MEMS infrastructure, we have devised a novel post-precessing sequence for the PolyMUMF'S process. T h u g h the use of this sequence, we show how to add, post hoc, a layer of dielectric between two previouslydeposited polysilicon films.We have demonstrated the effectiveness of these techniques through the successful fabrication and operation of untethered scratch drive actuators. Locomotion of these actuators is controlled by frequency modulation, and the devices achieve speeds of over 1.5 mdsec.