A Novel Coplanar Capacitive Micro-Displacement Sensor Combining Microfluidic Channels for Bridge Health Monitoring

High-resolution micro-displacement detection plays a pivotal role in the realm of bridge health monitoring. Capacitive micro-displacement sensors stand out among contact measurement methods due to their high detection resolution but are limited by measurement range. This paper proposes a high-sensitivity and wide-range micro-displacement measurement technique by combining microfluidic system and planar interdigital capacitor performance optimization methods. Through analysis and simulation of the interdigitated electrodes (IDEs) sensor under diverse electrode configurations, the 8-pair electrode design can reach a peak sensitivity of 0.124 pF/mm across the 0 to 50 mm detection range with a resolution of 4 mu m. To further boost the performance of the proposed microdisplacement measurement method, the integration of fractal structures into the electrode design has been explored, demonstrating a remarkable 1.5-fold sensitivity increase and a higher resolution of 2.6 mu m compared to IDE-based sensors of identical order. Besides, we designed an S-shaped microchannel deployed in areas with a strong electric field between electrodes, which has yielded an excellent linear response within a range of 0 to 4 mm and a nearly 2 times sensitivity enhancement. The research presented in this work may potentially contribute to the development of novel sensing methodologies for enhanced microdisplacement detection in bridge structures, ultimately leading to more accurate, efficient, and reliable structural health monitoring systems.