Piezo-Capacitive Flexible Pressure Sensor with Magnetically Self-Assembled Microneedle Array

Flexible pressure sensors are pivotal in advancing artificial intelligence, the Internet of Things (IoT), and wearable technologies. While microstructuring the functional layer of these sensors effectively enhances their performance, current fabrication methods often require complex equipment and time-consuming processes. Herein, we present a novel magnetization-induced self-assembly method to develop a magnetically grown microneedle array as a dielectric layer for flexible capacitive pressure sensors. By precisely controlling the magnetic particle concentration and dynamic magnetic field strength, we achieve a tunable microneedle morphology. The resulting sensor exhibits high sensitivity (4.11 kPa^-1), an ultrafast response time (20 ms), excellent cyclic stability (≈1700 cycles), and flexibility. We demonstrate real-time monitoring of various physiological signals including pulse, grip force, breathing rate, and head motion. This study introduces a promising approach for fabricating high-performance flexible sensors, potentially enabling more intuitive and effective human-machine interactions.