Virtual reality (VR) has been on the precipice of transforming how we interact with our worlds through technology for years. However, so far the haptic systems used in VR haven’t managed to provide a seamless user-friendly interface that can meet that promise. That could change with a new advanced wireless haptic interface system, dubbed WeTac, developed by researchers at the City University of Hong Kong (CityU). The system can provide the type of wireless interface that could act as a “second skin” that could help VR achieve its potential, said Yu Xinge, associate professor in the department of biomedical engineering (BME) at CityU, who led the research.
“Touch feedback has great potential, along with visual and audial information, in virtual reality (VR), so we kept trying to make the haptic interface thinner, softer, more compact, and wireless, so that it could be freely used on the hand , like a second skin,” he said in a post on CityU’s site.
WeTac is worn on the hand and forearm and collects personalized tactile sensation data that can be used to provide a robust touch experience in the metaverse, researchers said. It is soft and ultrathin and can integrate seamlessly with VR applications for gaming, sports, skills training, social activities, and even remote robotic controls, they said.
How the Haptic System Works
Haptic gloves currently provide the touch sensation in VR applications, but they typically mostly rely on bulky pumps and air ducts that are powered and controlled through cords and cables. This severely limits the immersive experience of both VR and augmented reality (AR) users, researchers said.
The electrotactile system of WeTac—which is composed of two parts—is lightweight, weighing only 19.2 grams, and small enough at 5 cm x 5 cm x 2.1 mm to be mounted on a user’s arm, researchers said. A miniaturized soft driver unit, attached to a forearm, acts as a control panel, while a hydrogel-based electrode hand patch that’s 220-µm to 1-mm thick acts as a haptic interface.
The WeTac patches provide programmable spatio-temporal feedback patterns, with 32 electrotactile stimulation pixels on the palm instead of only on the fingertips, researchers said. The average center-to-center distance between the electrodes is about 13 millimeters, which provides wide coverage for the entire hand, they said.
WeTac needs no external power source, running instead on a small rechargeable lithium-ion battery, and uses Bluetooth low energy (BLE) for wireless communication. Overall, the system offers great flexibility and can provide effective feedback when the user takes various poses and gestures, researchers said.
Solving Individual-User Challenges
Since no two VR users are alike, researchers had to solve several issues in the design of the system to ensure that its approach to use electrotactile stimulation would provide effective virtual touch for all types of people wearing it, Yu said. “As individuals have different sensitivities, the same feedback strength might be felt differently in different users’ hands,” he explained in the post.
To solve this issue, researchers customized the feedback parameters accordingly “to provide a universal tool for all users to eliminate another major bottleneck in the current haptic technology,” Yu said.
WeTac also is ultra-soft, which allows for threshold currents to be successfully mapped for individual users, determining the optimized parameters for each part of the hand, researchers said. Then, based on the personalized threshold data acquired by the haptic system, it can provide electrotactile feedback to any part of the hand on demand in a proper intensity range, they said.
This set-up can also avoid the unfortunate scenario of causing a user pain or, on the other end of the spectrum, being so weak that the user doesn’t feel it at all, researchers added. Moreover, the system has several built-in safety measures to protect users from electric shock, and maintains a temperature in the relatively low range of 27 degrees to 35.5 degrees Celsius to avoid overheating during continuous operation, researchers said.
Future of Virtual Reality?
The team published a paper on WeTac in the journal Nature Machine Intelligence. Researchers have already successfully integrated the system into VR and AR scenarios, synchronizing it with robotic hands through BLE communication, researchers said.
So far these initial applications have provided positive results, with users reporting that tactile feedback in the hand is much easier and more user friendly than with other VR haptic systems, they said. Users can actually feel virtual objects in various scenarios—including grasping a tennis ball in sports training, touching a cactus, or feeling a mouse running on the hand in social activities, researchers reported.
Researchers envision that WeTac can provide a haptic foundation for the future of virtual-touch solutions in not only VR and AR but also “for the development of the metaverse, human-machine interface (HMI), and other fields,” Yu said.