A mode-localized highly curved micro-beam for sensing applications

In this paper, we present an experimental and numerical investigation of a highly curved micro-resonator to enhance linear modal coupling between the symmetric and anti-symmetric modes for sensing applications. Specifically, we examine the phenomena of crossing, veering, and mode localization in micro-resonators with a high initial curvature-to- thickness ratio. A parametric study using the Finite Element Method (FEM) was conducted to adjust the strengthened mode coupling between the first symmetric and first antisymmetric modes. Experimental results on microbeams with high curvature ratios demonstrate that the higher-order modes effectively shift to become the fundamental ones. Moreover, its dynamic behavior and frequency responses were tested under varying electrostatic actuation levels and different electrode configurations at ambient and low-vacuum pressure ranges, demonstrating frequency modulation tuning between the two modes. Mode localization was successfully activated and tuned, resulting in a significant enhancement in pressure-sensing sensitivity. By tracking the frequency response in the mode localized zone, the device exhibited a high sensitivity of 174.6 ppm/Torr in the low-vacuum pressure range (100–760 Torr), which is seven times greater than obtained by tracking a single mode. Additionally, it achieved a sensitivity of 1144.3 ppm/Torr based on amplitude shifts within the 100–400 Torr range, without the need for an active power-consuming actuation. Hence, these results highlight the effectiveness of the proposed micro-device, which leverages passive geometric design to enable highly sensitive and energy-efficient sensing applications, offering a practical solution for applications requiring low power consumption and design simplicity. • A highly curved micro-resonator design is proposed to strengthen linear coupling between symmetric and anti-symmetric modes. • Both simulation and experimental studies confirmed that higher-order modes can effectively shift to becoming fundamental modes. • The device demonstrated tunable frequency responses under different actuation levels and electrode configurations. • Mode localization was successfully activated, yielding a pressure sensitivity of 174.6 ppm/Torr and up to 1144.3 ppm/Torr. • The passive geometric design achieves high sensitivity, making it ideal for low-power, practical sensing applications.