Low-voltage, high-sensitivity and high-reliability bimodal sensor array with fully inkjet-printed flexible conducting electrode for low power consumption electronic skin

Electronic skin, which has pixels composed of various functional sensors and can be applied to robots and various medical devices by mimicking the human skin, requires flexible, multi-mode, high-sensitivity, and low-interference sensors. In this study, we used a flexible electrode material comprised of organic conductor-elastomer-metal nanoparticles, as the core material and the inkjet printing method as the core process. These were used to form a flexible sensor for electronic skin applications, which involved vertically laminated sensors that utilize different sensing principles, thus enabling the realization of a flexible bimodal sensor with negligible interference. The pressure sensor with low resistivity and a flexible electrode, which was implemented using the sophisticated synthesis method, performed well under low-voltage (0.5 mV) operation conditions, exhibited pressure sensitivity over a wide range (3 Pa to 5 kPa), and showed excellent reliability characteristics (100,000 cycles) that can withstand severe mechanical stress. The temperature sensor, which was formed by a long bent organic conductor-metal line, changes its resistance with temperature, has a resistance change sensitivity of 0.32% per degree of temperature change, and exhibits a hysteresis-free temperature sensing capability. In particular, this device has maintained its robustness even over 5000 bending cycles. The 25 pixels temperature-pressure bimodal sensor array demonstrates very fast response rates, high sensitivity, and negligible interference performance. The low-resistivity/high-flexibility conducting electrode, inkjet printing process, device architecture, and integration scheme proposed in this study are expected to be widely used for electronic skin, multi-mode sensors, and flexible devices.