Enhancing the virtual experience with the touch sensation has become a hot topic, but
today’s haptic devices remain typically bulky and tangled with wires.
A team led by the City University of Hong Kong (CityU) researchers recently developed
an advanced wireless haptic interface system, called WeTac, worn on the hand, which has
soft, ultrathin features, and collects personalised tactile sensation data to provide a vivid
touch experience in the metaverse.
The system has application potential in gaming, sports and skills training, social activities,
and remote robotic controls.
The research findings were published in the scientific journal Nature Machine Intelligence
as the cover article.
Existing haptic gloves rely mostly on bulky pumps and air ducts, powered and controlled
through a bunch of cords and cables, which severely hinder the immersive experience of
VR and augmented reality (AR) users.
The newly developed WeTac overcomes these shortcomings with its soft, 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 Bluetooth low energy (BLE) wireless communication and a small rechargeable lithium-ion
battery.
The hand patch is only 220 µm to 1mm thick, with electrodes on the palm.
It exhibits great flexibility and guarantees effective feedback in various poses and gestures.
Electrotactile stimulation is a good method to provide effective virtual touch for users.
However, as individuals have different sensitivities, the same feedback strength might be felt differently
in different users’ hands.
So the researchers 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 faithfully reproduced over the whole hand.
The WeTac patches are worn on the hands to provide programmable spatio-temporal feedback
patterns, with 32 electrotactile stimulation pixels on the palm instead of the fingertips
only.
The average centre-to-centre distance between the electrodes is about 13mm, providing wide
coverage over the whole hand.
The device 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.
WeTac has been successfully integrated into VR and AR scenarios, and synchronised with
robotic hands through BLE communication.
With the miniature size, wearable and wireless format, and sensitivity-oriented feedback
strategy, WeTac makes tactile feedback in the hand much easier and user-friendly.
Users can feel virtual objects in different scenarios, such as grasping a tennis ball
in sports training, touching a cactus, or feeling a mouse running on the hand in social
activities, virtual gaming, etc.
The researchers believe that this is a powerful tool for providing virtual touching, and is
inspiring for the development of the metaverse, human-machine interface (HMI), and other fields.