Electronic skin imitates the tactile ability of human skin, and can measure sensitivity and external pressure. This cutting-edge technology can be implemented in various industries such as metaverse, robotics, and medical devices. Due to its high applicability, many researchers have attempted to develop a wide range of pressure sensors — a key component of the electronic skin. However, the currently available high-sensitivity pressure sensor has a narrow pressure detection range, while the wide-range pressure sensor lacks sensitivity. The trade-off between sensitivity and range in designing pressure sensors has been the major obstacle.

A research team led by Professor Jaewoong Jung of the School of Electrical Engineering announced that they have improved electronic skin for robots that serve two ends: higher sensitivity and wider detection range of pressure beyond that of human skin. The study, in which Dr. Simok Lee and Dr. Sanghyuk Byun participated as co-first authors, was published in the online version of the international journal Advanced Materials on October 3 under the title “Beyond the Human Touch Perception: An Adaptive Robotic Skin Based on Gallium Microgranules for Pressure Sensory Augmentation”.

The core material of the pressure sensor developed by the research team is gallium, a liquid metal at room temperature. Its low melting point  (29.76°C) facilitates the phase change between solid and liquid. The research team was thus able to control the rigidity of the sensor by changing the temperature. Applying this theoretical knowledge, they synthesized uniform gallium particles through a microfluidic-based production method, which maximized reliable mass production. With this product, users can easily switch between high-sensitivity detection mode (“rigid mode”) and wide-range pressure detection mode (“soft mode”) of the variable pressure sensor. The manufactured electronic skin showed 97% higher sensitivity and 262.5% wider pressure detection range compared to human skin. 

Professor Jung commented, “By applying the phase change of liquid metal, I believe that we will be able to develop electronic skins suitable for different purposes.” The research team proved that their electronic skin can be used in both situations where high sensitivity to pressure is required, such as pulse measurement, and situations where wide detection ranges are required, such as weight measurement.