A pressure sensor that operates stably without external interference even on a wet smartphone screen has been developed domestically. This pressure sensor achieves a level of tactile sensitivity comparable to that of humans.
KAIST announced on the 10th that Professor Junbo Yoon's research team from the Department of Electrical Engineering has developed a ‘nano-gap pressure sensor’ capable of detecting pressure with high resolution without being affected by external interferences such as 'ghost touch,' which occurs when water is on the smartphone screen after rain or shower.
(From left) Professor Yoon Jun-bo, Dr. Yang Jae-soon, (From top left) Integrated Master's and Doctoral Course student Jung Myung-geun, Professor Yoo Jae-young of Sungkyunkwan University. Provided by KAIST
Capacitive pressure sensors, commonly used in touch systems, have simple structures and excellent durability, making them widely used in ‘Human-Machine Interface’ technologies such as smartphones, wearable devices, and robots.
However, capacitive pressure sensors have been prone to malfunctions due to external interference factors such as water droplets, electromagnetic interference, and bending caused by curvature.
To solve these problems, the research team first identified the cause of interference in capacitive pressure sensors and confirmed that the ‘fringe field’ generated at the sensor edges is extremely vulnerable to external interference.
They concluded that suppressing the fringe field is essential to fundamentally resolve this issue. Through theoretical approaches focusing on structural variables affecting the fringe field, they revealed that narrowing the electrode gap to the scale of several hundred nanometers (nm) can suppress the fringe field generated by the sensor to a few percent (%) or less.
Based on this, the research team developed a nano-gap pressure sensor with an electrode gap of approximately 900 nm using proprietary micro- and nano-structure processing technology.
The developed sensor reliably detected pressure regardless of the material applying it and was verified to have no impact on sensing performance from bending or electromagnetic interference.
The research team also implemented an artificial tactile system utilizing the characteristics of the developed sensor. In human skin, a pressure receptor called Merkel's disc detects pressure. To mimic this, pressure sensor technology that responds only to pressure without reacting to external interference is required. However, existing technologies struggled to meet these conditions.
In contrast, the artificial tactile system overcomes all these limitations and achieves a density comparable to Merkel's disc, enabling precise wireless pressure detection.
Based on a series of research achievements, the team also verified that the magnitude and distribution of pressure can be obtained at high resolution without interference.
Professor Junbo Yoon said, “The biggest advantage of this nano-gap pressure sensor is that it operates stably without malfunctioning like existing pressure sensors even on rainy days or when sweating.” He added, “This can solve inconveniences many people have experienced in daily life and is expected to be applied in various fields such as precise tactile sensors for robots, medical wearable devices, and augmented reality (AR) and virtual reality (VR) interfaces.”
Meanwhile, this research was conducted with support from the Mid-career Researcher Support Program and Leading Research Center Support Program of the National Research Foundation of Korea. The study, led by Dr. Jaesoon Yang and PhD candidate Myunggeun Jeong from KAIST’s Department of Electrical Engineering, and Assistant Professor Jaeyoung Yoo from Sungkyunkwan University’s Department of Semiconductor Convergence Engineering (a KAIST PhD graduate), was also published in the international journal ‘Nature Communications’ on the 27th of last month.
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