Progress and challenges in flexible capacitive pressure sensors: Microstructure designs and applications

Pressure sensors are gaining increasing significance within the fields of bioelectronics and soft robotics. Among various types of pressure sensors, capacitive pressure sensors (CPSs) have garnered considerable attention due to their straightforward device design, efficient fabrication processes, low power consumption, and insensitivity to temperature variations. Although CPSs have been extensively utilized in clinical treatment, health monitoring, motion tracking, and human-machine interaction now, three crucial parameters of sensitivity, linearity, response time & recovery time remain far from reaching the ideal functionalization. Considerable effort has been made to improve sensing performance by employing distinct geometric microstructures for both the dielectric layer and electrodes. To comprehensively understand these microstructured devices and their working mechanisms, this review first introduces the theoretical of CPS, and then provides a brief overview of various materials and structures employed in CPS technology. With a focal point on the pivotal role of microstructures in shaping device performance, this review meticulously presents microstructures of diverse configurations, including pyramids, pillars, and domes, and further delves into their functionalization. Lastly, based on the prevailing challenges observed in CPS applications, this work offers a forward-looking perspective on potential research directions to advance the field.