The wireless skin-integrated electrotactile system comprises two parts: a soft driver unit (right), attached to the forearm, and the hand patch (left). Credit: City University of Hong Kong

The wireless skin-integrated electrotactile system's soft driver unit. Credit: City University of Hong Kong

Haptic interface system brings touch into the virtual world

15 December 2022

A team led by the City University of Hong Kong recently developed an advanced wireless haptic interface system, called WeTac, worn on the hand, which collects tactile sensation data to provide a vivid touch experience in the metaverse. 

Existing haptic gloves rely mostly on bulky pumps and air ducts, powered and controlled through a bunch of cords and cables, which hinder the immersive experience of virtual reality and augmented reality users. The WeTac overcomes these shortcomings with its ultrathin skin-integrated wireless electrotactile system.

The system comprises two parts: a miniaturised soft driver unit attached to the forearm as a control panel, and hydrogel-based electrode hand patch as a haptic interface. The entire driver unit weighs only 19.2g and is small enough to be mounted on the arm. It uses low energy wireless communication and a small rechargeable lithium-ion battery. The hand patch is only 220 µm to 1mm thin, with electrodes on the palm. It exhibits great flexibility and guarantees effective feedback in various poses and gestures.

It has several built-in safety measures to protect users from electric shock, and the temperature of the device is maintained in a relatively low range of 27 to 35.5°C to avoid causing any thermal discomfort during continuous operation.

A user interacts with a virtual tennis ball in VR using WeTac

The system has many potential applications in gaming, sports and skills training, social activities, and remote robotic controls. “Touch feedback has great potential in virtual reality, 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,” said Dr Xinge Yu, team leader and associate professor in the university's Department of Biomedical Engineering.

“Electrotactile stimulation is a good method to provide effective virtual touch for users,” Yu explained. “However, as individuals have different sensitivities, the same feedback strength might be felt differently in different users’ hands. So we need to customise the feedback parameters accordingly to provide a universal tool for all users to eliminate another major bottleneck in the current haptic technology.”

The ultra-soft feature of WeTac allows the threshold currents to be easily mapped for individual users to determine the optimised parameters for each part of the hand. Based on the personalised threshold data, electrotactile feedback can be delivered to any part of the hand on demand in a proper intensity range to avoid causing pain or being too weak to be felt. In this way, virtual tactile information, including spatial and temporal sequences, can be accurately reproduced over the whole hand.

“We believe that this is a powerful tool for providing virtual touch, and is inspiring for the development of the metaverse, human-machine interfaces, and other fields,” Yu said.

The team’s findings were recently published in the scientific journal Nature Machine Intelligence

To see a video of WeTac in action, click here.