(Invited) Skin-integrated Sensors and Haptic Interfaces for VR
Authors: Yu Xinge 
Published: July 2021

Technologies for virtual and augmented reality (VR and AR) create human experiences through visual and auditory stimuli that replicate sensations associated with the physical world. The most widespread VR/AR systems use head-mounted displays, accelerometers and speakers as the basis for three-dimensional, computer-generated environments that can exist in isolation or as overlays with actual scenery. By comparison to the eyes and the ears, the skin is a relatively underexplored sensory interface for VR/AR technology that could, nevertheless, greatly enhance experiences, at a qualitative level, with direct relevance in areas ranging from communications and social media, to gaming, entertainment and prosthetics technology. However, the research on soft wearable haptic interfaces is much less that of visual and auditory based ones. Since human body is soft, curved and time dynamic, developing wearable haptic interfaces is challenging. Recent advances in skin-integrated electronics provide a new insight for tactile sensing, however, the tactile feedback based on skin electronics is still in their infancies.
Here we present materials, device structures, power delivery strategies and communication schemes as the basis for a wireless, battery-free platform of electronic systems and haptic interfaces capable of softly laminating onto the skin to communicate information via spatio-temporally programmable patterns of localized mechanical vibrations. This system is also referred to as “epidermal VR”, where the haptic interface mounted on the skin can create a sense of touch via a programmable array of mechanical vibrating actuators. Based on the advanced mechanical design, the ultra-thin, skin-integrated haptic interfaces can be comfortably laminated onto near all the locations of the curved body surfaces. Moreover, the system is completely battery free, where the power are provided by RF input. In a 6 by 6 inches soft epidermal VR device, 32 mechanical vibrating actuators are integrated. Each actuator is designed resonating at skin most sensitive frequency (200 Hz), and can be individually controlled, programmed wirelessly. Low-modulus, soft silicone polymer is used as encapsulation materials and adhesion interfaces with skin. Therefore, the thin device can be directly wear on the skin without additional tapes or straps. The wireless communication is realized with near-field communication (NFC) technique, which is a very typical technology used in current smart phones. Therefore, touchscreen interfaces can wirelessly controlled the actuators in the epidermal VR device, and transmit the user’s touching commend to the soft device.
With such system, video chatting with virtually touch between friends and family members from different places will become true. Friends or family members can feel touching through the haptic interface in real time. A second representative application is in tactile feedback for use of robotic prosthetic devices. Of course, video game can be also updated to another level with such system. For example, a person who wears a suit with these epidermal VR embedded in can experience strikes just as the gaming character received in the game. More applications beyond entertainments are also covered by this system, such as robotic prosthetic control, sensing and feedback. For instance, a lower-arm amputee can sense a virtual haptic representation on the upper arm via an epidermal VR device.