Local Maximum Capacitance at Nonzero Lift-Off for Underwater Capacitive Sensing

Despite the popularity of capacitive sensors, limited research exists on their behavior underwater, which can be significantly different than those in air. This letter aims to address this gap by exploring the relationship between capacitance and lift-off distances. Through a combination of experimental investigations and numerical modeling, we identified a novel sensor phenomenon wherein capacitance exhibits a local maximum in response to incremental changes in distance. This resulted in a region with high capacitive sensitivity to distance. We modeled this phenomenon as dielectric losses in water and provided insights into its underlying mechanisms by analyzing capacitance in terms of its real and imaginary terms. We hope our study provides useful insights for future research and engineering applications for capacitive sensors underwater.