Micro-Buckled Shell Structured Fiber Electronics and Its Application in Wearable Devices

Nowadays, the flexible electronics is highly spotlighted in the recent wearable device fields, because it is easily grafted onto smart clothing, has strong durability, and has simple processes. In particular, the textile electronics is most suitable for smart clothing among the flexible electronics due to its advantage of easy sewing, light weight, and no foreign body sensation. Therefore, various studies to develop the performance of fiber electronics are ongoing, which is the most basic unit of textile electronics.<br/>The fiber electronics is widely used in wearable devices as diverse sensors. The fiber electronics-based sensors include mechanical sensors, which can detect pressure, strain, bending, torsion, etc., and chemical sensors, which can detect gas, temperature, pH, etc. A lot of researches are trying to improve the performance of fiber electronics-based sensors, especially some bio-inspired structural approaches helped greatly enhance the sensitivity of fiber sensors. However, the fiber electronics-based sensors have fatal limitation in that when external forces are applied, the reliability of the sensor rapidly reduced. In the case of piezoresistive type sensors, the resistance detection range of the sensor significantly changes under external forced condition, that cause the malfunction.<br/>In this study, a simple method is proposed to form micro-buckling structures on the surface of stretchable fiber electronics to overcome this problem and improve the performance of fiber electronics-based sensors through the structural approach simultaneously. We formed micro-sized buckled shell structure on the surface of the stretchable Ag conductive fiber with pre-strained chemical reduction method, and analyzed the optimized condition of buckling structure formation mechanism. The micro-buckling structures improve durability and reliability of stretchable fiber electronics-based sensors by preventing change of the base resistance when external strain or force is applied to the fiber electronics. Also, the micro-buckling structure greatly increases the sensitivity to target stimuli by allowing fiber electronics to have large surface area. Furthermore, we developed fiber electronics-based chemical sensors using micro-sized buckled shell structured stretchable conductive fibers. It showed higher sensitivity and reliability when micro-buckling structures were formed on the surface of working electrodes used in the pH sensor and temperature sensor.<br/>In future research, the stretchable fiber electronics with micro-buckling structure is expected to significantly contribute to improving the performance and stability of wearable devices by simultaneously perform as a stable interconnector and a reliable fiber electronics-based sensor. This study can expand to the medical field and the developed fiber electronics included wearable devices could be used as healthcare equipment that can check the body temperature or health status of patient in stable environment. This can be prepared to develop into a future treatment system that enables real-time patient monitoring and telemedicine.