Businesswoman on blurred background using virtual reality glasses technology 3D rendering

‘Epidermal VR’ gives technology human touch

Image credit: Sdecoret - Dreamstime

A joint research team from the US and Hong Kong have developed a skin-integrated wireless system that adds a sense of touch to any virtual-reality (VR) experience.

According to its creators, which consist of scientists and engineers from Northwestern University (US) and the City University of Hong Kong (CityU), the platform has great application potential in communications, prosthetic control and rehabilitation, as well as gaming and entertainment.

Referred to as an “epidermal VR” system, the device communicates touch through a fast, programmable array of miniature vibrating actuators embedded into a thin, soft, flexible material. These 15cm×15cm sheet-like prototypes comfortably laminate onto the curved surfaces of the skin without bulky batteries and cumbersome wires.

According to Dr Yu Xinge, an assistant professor at CityU, the actuators are breathable, reusable and functional at a full range of bending and twisting motions when on the user. Furthermore, the collection of chip-scale integrated circuits and antenna embedded into the device allows it to be powered and controlled wirelessly.

“The haptic actuators can harvest radio frequency power through the large flexible antenna within a certain distance, so the user wearing the device can move freely without the trouble of wires,” Dr Xinge explained.

The structure of the skin VR device

Functional components were integrated into a thin elastomeric layer with a thickness of only 3 mm. A total of 32 haptic actuators are controlled in 4 groups, by 8 independently controllable communication ports in the device.

Image credit: City University of Hong Kong

“People have contemplated this overall concept in the past, but without a clear basis for a realistic technology with the right set of characteristics or the proper form of scalability. Past designs involve manual assemblies of actuators, wires, batteries and combined internal and external control hardware,” said John A Rogers, a biometrics pioneer and a professor at Northwestern University.

“We leveraged our knowledge in stretchable electronics and wireless power transfer to put together a superior collection of components, including miniaturised actuators, in an advanced architecture designed as a skin-interfaced wearable device — with almost no encumbrances on the user.

“We feel that it’s a good starting point that will scale naturally to full-body systems and hundreds or thousands of discrete, programmable actuators.”

Northwestern’s Yonggang Huang, who co-led the research with Rogers, added: “We are expanding the boundaries and capabilities of virtual and augmented reality. By comparison to the eyes and the ears, the skin is a relatively underexplored sensory interface that could significantly enhance experiences.”

The device incorporates a distributed array of 32 individually programmable, millimetre-scale actuators, each of which generates a discrete sense of touch at a corresponding location on the skin. Each actuator resonates most strongly at 200 cycles per second, where the skin exhibits maximum sensitivity.

“We can adjust the frequency and amplitude of each actuator quickly and on-the-fly through our graphical user interface,” Rogers said. “We tailored the designs to maximise the sensory perception of the vibratory force delivered to the skin.”

This patch wirelessly connects to a touchscreen interface (on a smartphone or tablet), and when a user touches the touchscreen, that pattern of touch transmits to the patch. For example, if the user draws an “X” on the pattern on the touchscreen, the devices produce a sensory pattern, simultaneously and in real-time, in the shape of an 'X' through the vibratory interface to the skin.

When video chatting from different locations, friends and family members can reach out and virtually touch each other with negligible time delay and with pressures and patterns that can be controlled through the touchscreen interface.

“You could imagine that sensing virtual touch while on a video call with your family may become ubiquitous in the foreseeable future,” Huang said.

The actuators are embedded into an intrinsically soft and slightly tacky silicone polymer that adheres to the skin without tape or straps. Wireless and battery-free, the device also communicates through near-field communication (NFC) protocols, the same technology used in smartphones for electronic payments.

“With this wireless power-delivery scheme, we completely avoid the need for batteries, with their weight, size, bulk and limited operating lifetimes,” Rogers said. “The result is a thin, lightweight system that can be worn and used without constraint, indefinitely.”

The researchers said not only does the platform potentially add new dimensions to long-distance relationships and entertainment, but the device also provides prosthetics with sensory feedback and imparts telemedicine with a human touch.

The system developed by the team was integrated into the prosthetic arm of a US Army veteran, Garrett Anderson, who lost his right arm just below the elbow in 2005 when he was ambushed during his deployment in the Iraq War.

When wearing the patch on his upper arm, Anderson could feel sensations from his prosthetic fingertips transmitted to his arm. The vibrations felt more or less intense, depending on the firmness of his grip.

Application for the users of prostheses

The user wears the VR device (black part) on his upper arm. The sensor on the prosthetic hand can detect the shape of the object he grasped, and then generate a simulated 'touch' through the VR device, he can then perceive the shape of the object

Image credit: Dr Yu Xinge

“Say that I’m grabbing an egg or something fragile,” said Anderson, who is now the outreach coordinator at the University of Illinois’ Chez Veterans Center. “If I can’t adjust my grip, then I might crush the egg. I need to know the amount of grip that I’m applying so that I don’t hurt something or someone.”

According to Rogers, as people who have had amputations use the device, the experience could become more seamless.

“Users develop an ability to sense touch at the fingertips of their prosthetics through the sensory inputs on the upper arm,” Rogers explained. “Overtime, your brain can convert the sensation on your arm to a surrogate sense of feeling in your fingertips. It adds a sensory channel to reproduce the sense of touch.”

The researchers hope that the technology could eventually find its way into clothing, allowing people with prosthetics to wear VR shirts that communicate touch through their fingertips.

The research is published in the Nature journal.

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