A system of “electronic skin-integrated haptic interfaces” jointly developed by City University of Hong Kong (CityU) and other academic institutions can help users of prosthesis to feel the surrounding environment.

Dr. Yu Xinge (front row, left) and his research team at CityU. (Credit: City University of Hong Kong)

This novel system can transmit sensory stimuli to the body via the wireless actuator that converts energy to mechanical vibrations. It uses human skin as the sensory interface for virtual reality (VR) and augmented reality (AR).

The research achievement has recently been published in the journal Nature in an article titled “Skin-Integrated Wireless Haptic Interfaces for Virtual and Augmented Reality.”

“Our target is to develop electronic skin that can be comparable to human skin,” says Dr. Yu Xinge, the principal author of the article and assistant professor at CityU’s department of biomedical engineering. “Compared with similar types of equipment on the market, our new system is light and thin that can be tightly attached to human skin. Also, it’s wire free and battery free.”

New materials, device structures, power-delivery strategies, and communication schemes have been adopted by the research team to develop the system. By employing sophisticated structural mechanics design, the new soft skin device, which is composed of more than 700 functional components, has a thickness of less than 3 mm.

The newly developed system of skin-integrated haptic interfaces can help users of prostheses to feel the surrounding environment. (Credit: City University of Hong Kong)

Different layers of the device include a thin elastomeric layer as a reversible, soft adhesive interface to the skin, a silicone encapsulated functional layer that supports a wireless control system and a series of interconnected actuators, and an external layer of breathable fabric, which can be put together with wearable clothes.

“Conventional actuators that provide sensory vibrations require power of about 100 mW to transmit signals. However, as our new system uses radio frequency for power supply, it needs less than 2 mW to transmit signals and produce the same level of mechanical vibrations. Thus, we solved the difficult problem of transmission by low-power wireless function and significantly increased the distance of the operation for our system. This system not only saves power but also allows users to move more freely without the trouble of wires,” Yu says.

VR and AR technologies currently create human experiences through visual and auditory stimuli. However, compared with the eyes and ears, the skin is the largest sense organ of the body. Therefore, the sensory experience can be greatly enhanced by using the skin to sense the external environment.

The new system can help users of prostheses feel the external environment through the sense of touch and provide feedback to the users. In addition, it can be used for developing virtual scenes for clinical applications.

It took two years to complete the research project, which involves various disciplines such as mechanical engineering, materials science, biomedicine, physics, and chemistry. Yu says that the biggest challenge was to integrate different technologies.

“Biomedical engineering is meant to invent something that used to be impossible for us,” he says. “I’m grateful to CityU’s department of biomedical engineering for providing the research platform and to Prof. Sun Dong, head of the department, for his substantial support.”

Members of the research team include Northwestern University, University of Illinois at Urbana-Champaign, and Pennsylvania State University in the United States; University of Bristol in the UK; and Tsinghua University and Shandong University in China. The project was funded by CityU, Northwestern University, National Natural Science Foundation of China, and National Science Foundation of the United States.

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