Acoustically driven MEMS mirror enhanced by a parallel Helmholtz resonator array

Abstract In this study, we propose a method to enhance the actuation performance of an acoustically driven microelectromechanical systems (MEMSs) mirror that incorporates a parallel Helmholtz resonator (HR) array. Acoustic actuation enables a simple and noncontact device structure without on-chip actuating elements, which is particularly advantageous for mirror-based optical sensing devices that integrate surface-functional structures. However, the inherently limited energy of acoustic waves restricts the achievable vibration amplitude. Here, we propose inserting an HR array between the MEMS mirror and the acoustic source. The HR array selectively amplifies acoustic waves near its resonant frequency, and the acoustic actuation of the mirror is enhanced when this frequency matches its mechanical resonant frequency. A Si piezoresistive cantilever-type mirror was fabricated, and HR arrays were 3D-printed. Among configurations containing from one to six HRs, the six-HR array provided the highest amplification, nearly doubling the amplitude compared that obtained without using an HR. This approach offers a compact solution for large-amplitude MEMS actuation with potential applications in optical sensing and imaging.