KAIST

< Photo 1. (From left) Professor Jun-Bo Yoon and Dr. Jae-Soon Yang of KAIST with (top left) Myung-Kun Chung, a student of integrated master >

Recent advancements in robotics have enabled machines to handle delicate objects like eggs with precision, thanks to highly integrated pressure sensors that provide detailed tactile feedback. However, even the most advanced robots struggle to accurately detect pressure in complex environments involving water, bending, or electromagnetic interference. A research team at KAIST has successfully developed a pressure sensor that operates stably without external interference, even on wet surfaces like a smartphone screen covered in water, achieving human-level tactile sensitivity.

KAIST (represented by President Kwang Hyung Lee) announced on the 10th of March that a research team led by Professor Jun-Bo Yoon from the School of Electrical Engineering has developed a high-resolution pressure sensor that remains unaffected by external interference such as "ghost touches" caused by moisture on touchscreens.

Capacitive pressure sensors, widely used in touch systems due to their simple structure and durability, are essential components of human-machine interface (HMI) technologies in smartphones, wearable devices, and robots. However, they are prone to malfunctions caused by water droplets, electromagnetic interference, and curves.

< Figure 1. (Left) Schematic diagram of a smartphone surface that does not respond well to touch when wet on a rainy day. (Center) Schematic diagram of an unintended sensor malfunction in a situation where interference exists. (Right) Simulation results of electric field distribution in normal situations and situations where interference exists. When interference exists, distortion of the fringe field occurs. >

To address these issues, the research team investigated the root causes of interference in capacitive pressure sensors. They identified that the "fringe field" generated at the sensor’s edges is particularly susceptible to external disturbances.

The researchers concluded that, to fundamentally resolve this issue, suppressing the fringe field was necessary. Through theoretical analysis, they determined that reducing the electrode spacing to the nanometer scale could effectively minimize the fringe field to below a few percent.

< Figure 2. (Left) Photograph of the nano-gap pressure sensor developed in this study. (Center) Schematic diagram showing that the fringe field is suppressed due to the nano-gap design, effectively blocking external interference. (Right) Electron microscope image of the actually manufactured nano-gap pressure sensor. >

Utilizing proprietary micro/nanofabrication techniques, the team developed a nanogap pressure sensor with an electrode spacing of 900 nanometers (nm). This newly developed sensor reliably detected pressure regardless of the material exerting force and remained unaffected by bending or electromagnetic interference.

Furthermore, the team successfully implemented an artificial tactile system utilizing the developed sensor’s characteristics. Human skin contains specialized pressure receptors called Merkel’s disks. To artificially mimic them, the exclusive detection of pressure was necessary, but hadn’t been achieved by conventional sensors.

Professor Yoon’s research team overcame these challenges, developing a sensor achieving a density comparable to Merkel’s discs and enabling wireless, high-precision pressure sensing.

< Figure 3. (Left) Schematic diagram of a nano-gap pressure sensor that is free from interference and has high resolution to simulate the pressure detection method of the human body. (Right) A wireless artificial tactile system implemented using a nano-gap pressure sensor to pick up a wet object. It does not react even when water gets on the surface and only precisely detects pressure. >

To explore potential applications, the researcher also developed a force touch pad system, demonstrating its ability to capture pressure magnitude and distribution with high resolution and without interference.

Professor Yoon stated, “Our nanogap pressure sensor operates reliably even in rainy conditions or sweaty environments, eliminating common touch malfunctions. We believe this innovation will significantly enhance everyday user experiences.”

He added, “This technology has the potential to revolutionize various fields, including precision tactile sensors for robotics, medical wearable devices, and next-generation augmented reality (AR) and virtual reality (VR) interfaces.”

< Figure 4. (Left) Schematic diagram of the force touch pad system implemented using a nano gap pressure sensor and the situation where water is on the sensor. (Middle) Multi-touch measurement results using the force touch pad system in the situation where water is on the sensor. (Right) 3D measurement results that precisely show the size and distribution of pressure without interference or cross-interference by water on the sensor. >

The study was led by Jae-Soon Yang (Ph.D.), Myung-Kun Chung (Ph.D. candidate), and Jae-Young Yoo (Assistant Professor at Sungkyunkwan University, a KAIST Ph.D. graduate). The research findings were published in Nature Communications on February 27, 2025. (Paper title: “Interference-Free Nanogap Pressure Sensor Array with High Spatial Resolution for Wireless Human-Machine Interface Applications”, DOI: 10.1038/s41467-025-57232-8)

This study was supported by the National Research Foundation of Korea’s Mid-Career Researcher Program and Leading Research Center Support Program.