기초과학연구원(IBS, 원장 노도영) 나노의학 연구단 박장웅 연구위원(연세대 신소재공학과 교수) 연구팀은 세브란스병원 신경외과 정현호 교수 연구팀과 공동으로 압력 센서를 전기 촉각 디바이스에 결합해 디스플레이에서 일관된 촉각을 구현하고, 뇌파를 기반으로 촉각 정보를 분류해 9가지 이상의 다양한 촉감을 구현하는 기술을 개발했다.
▲When the device is in operation, tactile information matching the video is transmitted simultaneously with pressure sensing, and the user can perceive the ball rolling through virtual electrotactile sensation implemented at the tip of the finger even with their eyes covered.
Transparent haptic display, real-world textures from fur to glass
The development of a virtual tactile implementation technology for displays that allows all users to experience the same tactile sensation is expected to enable the spread of tactile content in AR and VR devices.
The research team of Park Jang-woong, a research fellow at the Nanomedicine Research Group of the Institute for Basic Science (IBS, President Noh Do-young) and a professor of materials science and engineering at Yonsei University, in collaboration with the research team of Professor Jeong Hyeon-ho of the Department of Neurosurgery at Severance Hospital, developed a technology that implements consistent tactile sensation on a display by combining a pressure sensor with an electrotactile device and classifies tactile information based on brain waves to implement more than nine different tactile sensations.
As close interaction between users and technology becomes more important in technologies such as virtual reality (VR) and augmented reality (AR), virtual tactile implementation technology has emerged to provide an immersive user experience by connecting the virtual world and reality.
Among them, vibrotactile technology that uses physical stimulation cannot directly transmit tactile sensation because the vibration actuator is opaque and arranged above the display. Accordingly, electrotactile technology that artificially creates a sense of touch using electrical stimulation is attracting attention as a next-generation technology.
When we feel touch, tactile sensory cells distributed in the skin convert tactile information into electrical signals and transmit them to the brain.
The principle of electrotactile technology is to artificially generate electrical signals containing this tactile information.
On the other hand, existing electric tactile devices had high resistance and required a lot of current, which caused safety issues.
In addition, since the force with which each user presses the device is different, the contact state becomes unstable, and the tactile sensation felt by the same electrical stimulation can vary, making it difficult to implement a consistent tactile sensation.
In addition, there were limitations to commercialization because subjective information such as tactile sensation could not be standardized.
To solve this problem, the research team created a 'transparent interferometric electrotactile device' capable of pressure compensation.
The device consists of an electrode part that implements electrotactile sensation and a pressure sensor that compensates for the pressure of the finger.
First, platinum nanoparticles were plated on an indium-tin oxide-based electrode to maintain transparency and lower the resistance of the electrode.
As a result, safety was secured by reducing the electrode resistance by more than five times, and a high transmittance of approximately 90% was achieved.
Additionally, a pressure sensor was integrated to measure and compensate for finger pressure, resulting in consistent electrotactile sensation.
Furthermore, we conducted a Somatosensory Evoked Potential test to standardize the sense of touch in order to actually implement a specific sense of touch. By analyzing how the user's brain signals react when the current density and frequency of the electrotactile sensation change, we were able to classify the sense of touch. As a result, the research team implemented more than nine different types of electrotactile sensations, ranging from hair to glass.
The core of this study is the introduction of interference phenomenon into electrotactile technology. Interference phenomenon is a phenomenon in which the frequency and amplitude change when two electromagnetic fields overlap. Compared to the existing ones, the same tactile intensity was realized with only 30% lower current, and the stimulation location was controlled more precisely, improving the tactile resolution by 32%.
This is the highest level of tactile resolution among existing electrotactile technologies, including Teslasuit, and opens up possibilities for innovation in VR and AR technologies as well as in the display field. In fact, the developed technology was successfully combined with a smartphone display to implement virtual tactile sensations for objects in a video.
“Through electrotactile technology, we can integrate tactile information that matches the visual information of the display and deliver it to the user,” said Park Jang-woong, a researcher who led the research. “This study is expected to contribute to further activating the interaction between users and devices in various AR, VR, and smart devices through electrotactile technology based on interference stimulation.”
The results of this study were published in the international academic journal 'Nature Communications' on September 3 (Korean time).