A novel high-sensitivity triaxial accelerometer based on 3-D phononic crystals.

High-sensitivity triaxial acceleration sensing is widely applied from consumer electronics to inertial navigation. However, Conventional triaxial accelerometers are mainly rely on assembling multiple single-axis transducers, which increases device size and complexity. The acceleration-sensing mechanism of phononic crystals (PnCs) has demonstrated significant potential for high-sensitivity detection, owing to the high-quality factor of their resonant cavities. In this paper, based on the theory of 2-D PnCs single-axis acceleration sensing, we propose a novel triaxial accelerometer based on 3-D PnCs. Specifically, a point defect is introduced along the x and y axis, while a line defect is created along the z axis. Defective PnCs create a resonant cavity that produces sharp transmission peaks within the band gap. Acceleration causes a frequency shift in these peaks. This study employs the finite element method (FEM) to calculate the band structure of the 3-D PnCs, as well as the transmission spectra along all three axes. Both numerical and experimental results indicate that this approach is suitable for high-sensitivity triaxial acceleration sensing. The experimentally measured sensitivities along the x, y, and z axes are 1.58 kHz/g, 0.62 kHz/g, and 0.43 kHz/g, respectively, with corresponding measurement bandwidths of 37.1 Hz, 15.9 Hz, and 37.4 Hz. This innovative design based on 3-D PnCs enables triaxial high-sensitivity acceleration sensing within a single structural configuration and holds promise for future integration with ultrasonic transducers to form a compact microsystem.