Scalable Fabrication of Flexible Single‐Layer Strain and Double‐Layer Pressure Sensors by Inkjet Printing for Subtle Vibration Detection

Abstract Flexible sensors have attracted tremendous attentions in subtle force/vibration detection, human motion/health monitoring, and other related application fields. Although various sensors are developed to meet this growing demand, it is still a huge challenge to prepare satisfactory sensors with ultrahigh sensitivity and superior stability. In this work, a double‐layer flexible sensor is successfully prepared via an efficient and designable inkjet printing approach. Metallic silver layers are deposited onto polyurethane acrylate substrates with or without microstructures to form the flexible electrodes. The combination of a flat electrode and a microstructured electrode finally becomes a durable double‐layer flexible sensor with ultrahigh sensitivity and superior stability. Besides, the flexible flat electrodes can also be applied as single‐layer sensors. An ultrahigh sensitivity (maximum gauge factor of > 1100), favorable durability ( > 1000 cycles), and fast response time ( ≈ 90 ms) are achieved simultaneously in a flat single‐layer sensor, while the combined double‐layer sensor presents quick response capability to small pressures ( ≈ 250 Pa). Moreover, these single‐layer and double‐layer sensors can monitor a variety of physiological signals (e.g., human pulse waveform, breathing behavior, and voice recognition), indicating their promising applications in wearable electronics.