Wearable multimodal tactile interfaces for augmenting haptic perception

Haptic feedback has been used to faithfully restitute the haptic sense lacking during telemanipulation, but also for providing auxiliary information via the haptic channel to restore functional perception of missing or damaged senses, e.g. sensory substitution for the visually impaired. Yet, despite the growing number of applications that would benefit from haptic feedback, its penetration rate remains low. We have identified three under-researched features of haptic feedback that we believe are necessary to break the bottleneck: multimodality, thermal feedback and wearability. Indeed, while haptic perception results from the integration of multiple somatosensory inputs, the interactions between haptic modalities have rarely been investigated. Thermal feedback is an ideal candidate to explore these interactions as skin temperature is known to modulate the sensitivity of skin receptors. Finally, although haptic perception is distributed over the entire body, most multimodal haptic devices are still bulky and rigid, thus limiting their usage to specific body parts and applications. As the integration of multiple feedback modalities into a flexible display is complex, the benefits of these three features need to be demonstrated. This motivated the developments presented in this thesis. First, we miniaturized and integrated thermal feedback in multisensory platforms to investigate its role in conveying non-sensory information and modulating tactile perception. The first study showed that users are able to distinguish the temperature difference between two adjacent thermal stimuli presented under the fingertip by a high-density thermal display, highlighting the potential of miniaturized displays to deliver thermally-encoded information through small skin areas. A second study showed that modifying the skin temperature yielded changes in the precision of stiffness judgments up to 22.3%, suggesting that thermal feedback can be used to modulate the perception of complex haptic percepts. Moving towards complete wearability, we introduced a wearable multimodal display that matches the skin curvature to deliver thermo-tactile cues optimally, as supported by the high users’ identification rates of simulated materials. Subsequently, we developed a portable hydraulic actuation that generates multimodal tactile feedback in remote 3D-printed flexible displays, paving the way to truly versatile wearable multimodal displays. Finally, a tactile suit remapping tactile and proprioceptive sensations from the virtual legs of an avatar onto the upper limbs of paraplegic patients is developed. We show that the patients were able to perceive the position of the virtual legs based on tactile feedback alone, that the use of tactile feedback in synchrony with the avatar’s walk changed the perception of the boundaries of their body, and that the modulation of the tactile stimulation induced a robust sensation of walking on different floors. These results demonstrate the potential of wearable tactile displays to create perceptual orthoses. In this work, we have developed the tools to deliver a multimodal tactile stimulation using wearable thermo-tactile displays and have shown how their unique features can impact fields such as surgical and rehabilitation robotics. These findings encourage the future development of wearable multimodal tactile displays taking advantage of the synergies between haptic modalities to improve teleoperation and sensory rehabilitation.