It is difficult for standard sensors to detect the subtle skin movement on the bridge of the nose during inhalation. However, Professor Daeshik KANG (ME) and Dr. Jieun PARK (ME), along with Dr. Minho KIM and Dr. Taewi KIM from Ajou University, developed an ultra-sensitive sensor to capture these movements.

The team developed a nanometer-scale thin and flexible gold sensor, increasing sensitivity by controlling microscopic fissures that form on the surface of the gold. The depth of the cracks formed in the gold is the key to this sensor; deeper cracks result in more significant electrical signal changes with even slight movements.

To prevent electrical cut-off due to overly deep cracks, a “semi-cured polyimide” interlayer, half-hardened at 200°C, is placed under the electrode. This reduces the resistance during the gold growth process, creating a structure that does not break easily while remaining extremely sensitive to subtle changes.

The sensor recorded a Gauge factor of 100,000 in a situation where the strain was only 2%—50 times more sensitive than existing gold-based sensors. When a breathing experiment was conducted, it clearly detected the nose skin movement, and the measured signal matched the actual breathing pattern without any user discomfort. It additionally showed the potential to be used as a new physical signal detection technology to replace existing respiratory measurement equipment.

Prof. Kang stated, “By precisely controlling the microscopic growth of gold, we have implemented a sensor that responds to even the smallest movement while operating stably. It can be utilized in various fields such as wearable devices and soft robots.”