Vincent Levesque

Haptic wearables such as smartwatches are increasingly available, yet rarely used in coordination with vibrating handheld controllers to enhance VR experiences. In this work, we explore such cross-device haptic effects between controllers, wristbands and a backpack in three exemplar activities (Pistols, Bow & Arrow, Hammer). A user study (N=24) was conducted to compare these cross-device haptic effects with single-device haptic effects relying on the controllers alone. Questionnaire responses revealed few differences between the two modes, but discussions with participants suggest an appreciation for cross-device haptics for at least some activities.

Most studies of haptic illusions assume that the actuators used are identical and therefore produce vibrations with the same frequency. We ran two experiments to investigate the effect of mismatched vibratory frequencies on the perception of apparent tactile motion. We simulated having actuators with different properties by changing the frequency and amplitude of vibrations produced by a wideband actuator. We varied frequencies from 50 to 250 Hz with adjusted amplitudes to normalize the perceived intensity. The results suggest that the apparent tactile motion illusion is robust to mismatches in the resonant frequency of actuators and that it can therefore be produced by pairs of haptic devices with different specifications.

We review the current technology underlying surface haptics that converts passive touch surfaces to active ones (machine haptics), our perception of tactile stimuli displayed through touch surfaces (human haptics), their potential applications (human-machine interaction), and finally the challenges ahead of us in making them available through commercial systems. This review primarily covers the tactile interactions of human fingers or hands with surface-haptics displays by focusing on the three most popular actuation methods: vibrotactile, electrostatic, and ultrasonic.

ReFlex is a flexible smartphone with bend input and active haptic feedback. ReFlex's features allow the introduction of sensations such as friction or resistance. We report results from an experiment using ReFlex in a targeting task, as well as initial users' reactions to the prototype. We explore both absolute and relative tactile haptic feedback, paired with two types of bend input mappings: position-control and rate-control. We observed that position-controlled cursors paired well with relative bend feedback, while rate-controlled cursors paired well with absolute bend feedback to indicate targets. We also explored an eyes-free condition. Results suggest that while eyes-free, haptic feedback conditions were more error-prone than visual-only conditions, the size of the error was relatively small, and users were able to complete the task in all cases. We present two application scenarios that take advantage of the unique input and output modalities of ReFlex and discuss its potential for within document navigation.

Many aspects of both grip function and tactile perception depend on complex frictional interactions occurring in the contact zone of the finger pad, which is the subject of the current review. While it is well established that friction plays a crucial role in grip function, its exact contribution for discriminatory touch involving the sliding of a finger pad is more elusive. For texture discrimination, it is clear that vibrotaction plays an important role in the discriminatory mechanisms. Among other factors, friction impacts the nature of the vibrations generated by the relative movement of the fingertip skin against a probed object. Friction also has a major influence on the perceived tactile pleasantness of a surface. The contact mechanics of a finger pad is governed by the fingerprint ridges and the sweat that is exuded from pores located on these ridges. Counterintuitively, the coefficient of friction can increase by an order of magnitude in a period of tens of seconds when in contact with an impermeably smooth surface, such as glass. In contrast, the value will decrease for a porous surface, such as paper. The increase in friction is attributed to an occlusion mechanism and can be described by first-order kinetics. Surprisingly, the sensitivity of the coefficient of friction to the normal load and sliding velocity is comparatively of second order, yet these dependencies provide the main basis of theoretical models which, to-date, largely ignore the time evolution of the frictional dynamics. One well-known effect on taction is the possibility of inducing stick–slip if the friction decreases with increasing sliding velocity. Moreover, the initial slip of a finger pad occurs by the propagation of an annulus of failure from the perimeter of the contact zone and this phenomenon could be important in tactile perception and grip function.

We investigate gains in user appreciation and performance when the level of detail of tactile graphics is dynamically altered either at the press of a button or automatically, as a function of exploration speed. This concept was evaluated by asking 9 visually impaired participants to perform hierarchical spatial search tasks in a concert hall illustration. The tasks could be simplified by first searching for a section in a sparse illustration, and then a seat in a detailed illustration. The results show no improvement in task performance but indicate a user preference for explicitly controlling the level of details with the manual toggle.

Scrolling interactions are an important aspect of the design of usable touchscreen interfaces, particularly for handheld devices that can only display a limited amount of information at once. Using a touchscreen capable of dynamically altering its surface friction, we explore the design space of haptically-augmented scrolling interactions and investigate programmable friction's ability to provide appropriate feedback in envisioned usage scenarios. We performed five user experiments to evaluate respectively the identifiability of a set of iconic detents, the countability of detents, the perception of detent density, the synchronization of tactile feedback to on-screen events, and the optimal friction pattern for a spring-like resistance. The results of these experiments provide valuable information that will inform the design of scrolling interactions that leverage programmable friction for an improved user experience.

The dynamics of fingertip contact manifest themselves in the complex skin movements observed during the transition from a stuck state to a fully developed slip. While investigating this transition, we found that it depended on skin hydration. To quantify this dependency, we asked subjects to slide their index fingertip on a glass surface while keeping the normal component of the interaction force constant with the help of visual feedback. Skin deformation inside the contact region was imaged with an optical apparatus that allowed us to quantify the relative sizes of the slipping and sticking regions. The ratio of the stuck skin area to the total contact area decreased linearly from 1 to 0 when the tangential force component increased from 0 to a maximum. The slope of this relationship was inversely correlated to the normal force component. The skin hydration level dramatically affected the dynamics of the contact encapsulated in the course of evolution from sticking to slipping. The specific effect was to reduce the tendency of a contact to slip, regardless of the variations of the coefficient of friction. Since grips were more unstable under dry skin conditions, our results suggest that the nervous system responds to dry skin by exaggerated grip forces that cannot be simply explained by a change in the coefficient of friction.