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Understanding and controlling modal coupling in micro/nanomechanical devices is integral to the design of high-accuracy timing references and inertial sensors. However, insight into specific physical mechanisms underlying modal coupling, and the ability to tune such interactions is limited. Here, we demonstrate that tuneable mode coupling can be achieved in capacitive microelectromechanical devices with dynamic electrostatic fields enabling strong coupling between otherwise uncoupled modes. A vacuum-sealed microelectromechanical silicon ring resonator is employed in this work, with relevance to the gyroscopic lateral modes of vibration. It is shown that a parametric pumping scheme can be implemented through capacitive electrodes surrounding the device that allows for the mode coupling strength to be dynamically tuned, as well as allowing greater flexibility in the control of the coupling stiffness. Electrostatic pump based sideband coupling is demonstrated, and compared to conventional strain-mediated sideband operations. Electrostatic coupling is shown to be very efficient, enabling strong, tunable dynamical coupling.

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Surface acoustic wave (SAW) devices using embedded interdigital transducers (IDTs) on an AlN/diamond/Si layered substrate are fabricated, and their performances are investigated. The Sezawa mode is the dominant resonance with the highest resonant frequency up to 17.7 GHz, a signal amplitude of 20 dB, and an electromechanical coupling coefficient of 0.92%. Comparing these SAW devices with those having the conventional IDTs on the same layered structure, the output SAW power and resonant frequency of devices are improved by 10.7% and 1.1%, respectively, for the embedded IDT devices. This is because the different field distribution leads to the different Bragg reflection and phase velocity for the two types of IDTs. The radiation frequency characteristics indicate that the advantages of the embedded IDTs would be useful for high frequency, high power applications such as monolithic integrated millimeter-wave integrated circuit and high speed communications.

A new approach to improve the performance of a butterfly gyroscope is developed. The methodology provides a simple way to improve the gyroscope’s sensitivity and stability, by reducing the resonant frequency mismatch between the drive and sense modes. This method was verified by simulations and theoretical analysis. The size of the hexagonal section oblique beam is the major factor that influences the resonant frequency mismatch. A prototype, which has the appropriately sized oblique beam, was fabricated using precise, time-controlled multilayer pre-buried masks. The performance of this prototype was compared with a non-tuned gyroscope. The scale factor of the prototype reaches 30.13 mV/ ˚/s, which is 15 times larger than that obtained from the non-tuned gyroscope. The bias stability of the prototype is 0.8 ˚/h, which is better than the 5.2 ˚/h of the non-tuned devices.

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