A review onin situstiffness adjustment methods in MEMS

Abstract

In situ stiffness adjustment in microelectromechanical systems is used in a variety of applications such as radio-frequency mechanical filters, energy harvesters, atomic force microscopy, vibration detection sensors. In this review we provide designers with an overview of existing stiffness adjustment methods, their working principle, and possible adjustment range. The concepts are categorized according to their physical working principle. It is concluded that the electrostatic adjustment principle is the most applied method, and narrow to wide ranges in stiffness can be achieved. But in order to obtain a wide range in stiffness change, large, complex devices were designed. Mechanical stiffness adjustment is found to be a space-effective way of obtaining wide changes in stiffness, but these methods are often discrete and require large tuning voltages. Stiffness adjustment through stressing effects or change in Young’s modulus was used only for narrow ranges. The change in second moment of inertia was used for stiffness adjustment in the intermediate range.

Micromechanical Characterization of Polysilicon Films through On-Chip Tests

“…Even though microelectromechanical systems (MEMS) have proven to be potential candidates for a wide range of applications, such as gyroscopes, accelerometers, biosensors, switches and magnetometers, the design uncertainties are still a challenging issue when new devices have to be designed. These uncertainties are recognized to be of crucial importance to the performance of MEMS; a family of in situ methods has been therefore developed in the MEMS design community to adjust the mechanical stiffness of deformable components and, so, compensate for the performance inaccuracies after fabrication; see, e.g., [ 1 ]. The advances in the microfabrication process and the continuous demand of miniaturization may amplify the impact of these uncertainties when the reliability and reproducibility of the systems are of concern.…”

Load Sensor Instability and Optimization of MEMS-based Tensile Testing Devices

“…Currently, stiffness tuning finds application in many systems, like atomic force microscopy (AFM) (Mueller-Falcke et al, 2004) and, above all, microresonators (Kozinsky et al, 2006) and the strategies adopted in those cases can be borrowed and transferred to the context of tensile testing devices, too. In particular, among the broad range of available options, solutions based on either an electrostatic or a mechanical working principle are the most interesting, since they allow for the highest stiffness increase (de Laat et al, 2016). In the first case, a voltage is applied between moving and fixed electrodes in order to produce an electrostatic force that causes an increase or reduction of the overall system stiffness, depending on the system design (de Laat et al, 2016).…”

“…In particular, among the broad range of available options, solutions based on either an electrostatic or a mechanical working principle are the most interesting, since they allow for the highest stiffness increase (de Laat et al, 2016). In the first case, a voltage is applied between moving and fixed electrodes in order to produce an electrostatic force that causes an increase or reduction of the overall system stiffness, depending on the system design (de Laat et al, 2016). In the second case, the overall system stiffness can be increased by causing the moving shuttle to engage more flexural elements.…”

“…In the second case, the overall system stiffness can be increased by causing the moving shuttle to engage more flexural elements. Such engagement can be induced by applying a critical voltage causing the pull-in of the moving shuttle to the additional springs (de Laat et al, 2016).…”

Thermal- and Piezo-Tunable Flexural-Mode Resonator With Piezoelectric Actuation and Sensing

“…One of the main problems affecting MEMS resonators consists of resonant frequency shifts arising from changes in the ambient conditions (variations of temperature and pressure) or fabrication process uncertainties (variations of geometrical dimensions and material properties, residual stress) [6]. Therefore, capability of active frequency tuning that is repeatable and reversible is a vital feature for MEMS resonators to work effectively on a specific frequency [7].…”