Thin-Film AlN-on-Silicon Resonant Gyroscopes: Design, Fabrication, and Eigenmode Operation

Resonant MEMS gyroscopes have been rapidly adopted in various consumer, industrial, and automotive applications thanks to the significant improvements in their performance over the past decade. The current efforts in enhancing the performance of high-precision resonant gyroscopes are mainly focused on two seemingly contradictory metrics, larger bandwidth and lower noise level, to push the technology towards navigation applications. The key enabling factor for the realization of low-noise high-bandwidth resonant gyroscopes is the utilization of a strong electromechanical transducer at high frequencies. Thin-film piezoelectric-on-silicon technology provides a very efficient transduction mechanism suitable for implementation of bulk-mode resonant gyroscopes without the need for submicron capacitive gaps or large DC polarization voltages. More importantly, in-air operation of piezoelectric devices at moderate Q values allows for the cointegration of mode-matched gyroscopes and accelerometers on a common substrate for inertial measurement units. This work presents the design, fabrication, characterization, and method of mode matching of piezoelectric-on-silicon resonant gyroscopes. The degenerate in-plane flexural vibration mode shapes of the resonating structure are demonstrated to have a strong gyroscopic coupling as well as a large piezoelectric transduction coefficient. Eigenmode operation of resonant gyroscopes is introduced as the modal alignment technique for the piezoelectric devices independently of the transduction mechanism. Controlled displacement feedback is also employed as the frequency matching technique to accomplish complete mode matching of the piezoelectric gyroscopes.Ph.D

MEMS Gyroscopes for Consumers and Industrial Applications

none2mixedAntonello, Riccardo; Oboe, RobertoAntonello, Riccardo; Oboe, Robert

Vibrating Flexoelectric Micro-Beams as Angular Rate Sensors

We studied flexoelectrically excited/detected bending vibrations in perpendicular directions of a micro-beam spinning about its axis. A set of one-dimensional equations was derived and used in a theoretical analysis. It is shown that the Coriolis effect associated with the spin produces an electrical output proportional to the angular rate of the spin when it is small. Thus, the beam can be used as a gyroscope for angular rate sensing. Compared to conventional piezoelectric beam gyroscopes, the flexoelectric beam proposed and analyzed has a simpler structure

Vibrating Flexoelectric Micro-Beams as Angular Rate Sensors

We studied flexoelectrically excited/detected bending vibrations in perpendicular directions of a micro-beam spinning about its axis. A set of one-dimensional equations was derived and used in a theoretical analysis. It is shown that the Coriolis effect associated with the spin produces an electrical output proportional to the angular rate of the spin when it is small. Thus, the beam can be used as a gyroscope for angular rate sensing. Compared to conventional piezoelectric beam gyroscopes, the flexoelectric beam proposed and analyzed has a simpler structure

Micromechanical actuators for insect flight mechanics

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references (p. 95-97).This project aims to develop MEMS actuators to aid in the study of insect flight mechanics. Specifically, we are developing actuators that can stimulate the antennae of the crepuscular hawk moth Manduca Sexta. The possible mechanosensory function of antennae as airflow sensors has been suggested, and recent discoveries of our collaborators reveal that mechanosensory input from the antennae of flying moths serves a similar role to that of the hind wings of two-winged insects, detecting Coriolis forces and thereby mediating flight stability during maneuvers. Early evidence suggests that mechanical stimulus of the antennae may enable flight control. In addition, the crepuscular hawk moth Manduca Sexta has a wide wingspan (~110 mm) and is capable of carrying at least one quarter of its own weight. Thus, studying the flight of Manduca Sexta by attachment of microsystems seems plausible. The goal of our project is to design and fabricate micromechanical actuators, which will be mounted onto the moth antennae. Our collaborators will study the flight control mechanism by mechanical stimulation. Our first step was to fabricate "dummy" silicon rings for our biologist collaborators for implant experiment. A series of mounting kits were developed, and due to the nature of the moth antennae, ring-beam-ring construction was finally designed and fabricated, like a "shackle", to meet the mounting requirements. Next, we integrated actuators onto the mounting kit. Piezoelectric film/sheet, piezoelectricbender and piezoelectric-stack were considered as the actuators. Live testing was also taken while the moth was resting or flapping its wings. The moth apparently responds to the mechanical stimulus under both circumstances, by swinging its wings and abdomen. Actuation amplifier was also modeled and tested, which might be used for future mechanical stimulators.by Hui Zhou.S.M

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

Micro-Resonators: The Quest for Superior Performance

Microelectromechanical resonators are no longer solely a subject of research in university and government labs; they have found a variety of applications at industrial scale, where their market is predicted to grow steadily. Nevertheless, many barriers to enhance their performance and further spread their application remain to be overcome. In this Special Issue, we will focus our attention to some of the persistent challenges of micro-/nano-resonators such as nonlinearity, temperature stability, acceleration sensitivity, limits of quality factor, and failure modes that require a more in-depth understanding of the physics of vibration at small scale. The goal is to seek innovative solutions that take advantage of unique material properties and original designs to push the performance of micro-resonators beyond what is conventionally achievable. Contributions from academia discussing less-known characteristics of micro-resonators and from industry depicting the challenges of large-scale implementation of resonators are encouraged with the hopes of further stimulating the growth of this field, which is rich with fascinating physics and challenging problems

Nonlinear Dynamics of a Class of Ring-based Angular Rate Sensing and Energy Harvesting Systems

This research is classified into two broad sections: ring-based MEMS (Micro-electro Mechanical Systems) and macro gyroscopes and novel bi-stable/monostable nonlinear energy harvesting systems. In both cases, models and solution methods are based on ring structural dynamics considering comprehensive nonlinear formulations. The investigation of nonlinear and linear dynamic response behavior of MEMS and macro ring gyroscopes forms the basis of the first study. This class of MEMS/macro ring-based vibratory gyroscopes requires oscillatory nonlinear electrostatic/electromagnetic excitation forces for their operation. The partial differential equations that govern the ring dynamics are reduced to a set of coupled nonlinear ordinary differential equations by assuming nonlinear and linear mode functions and via the application of Galerkin\u27s procedure. Understanding the effects of nonlinear actuator dynamics via suitable modeling is considered essential and adequately addressed. An external excitation of the ring gyroscope at a frequency close to the system resonant frequency is necessary to increase operational sensitivity. The variation of natural frequencies has been examined theoretically and experimentally. Nonlinear and linear dynamic responses in the driving and sensing directions are examined via time responses, phase diagram, Poincare’ map, and bifurcation diagram in the presence of input angular motion and the excitation forces. The second part of this research focuses on the design, modeling, and dynamic analysis of novel macro and MEMS ring energy harvesting systems. This study is concerned with nonlinear dynamic analysis of both bistable and monostable ring structure-based energy-harvesting systems. The ring structural elements in this class of harvesters are considered as an alternative to the previously used beam and tube structural configurations. Comprehensive mathematical models for the proposed nonlinear and linear ring harvester systems and nonlinear magnetic and electrostatic forces that act on the ring structure are formulated. Ambient sinusoidal excitations in a broad range of frequencies are considered as the energy source to the harvester. Consideration of the harvester system nonlinearities and the nonlinear external magnetic force results in system bi-stability and an increased ii frequency range. Also, external excitation of the ring-based nonlinear harvester at a frequency close to the system resonant frequency associated with the second flexural mode is essential to increase operational efficiency. Ring-based bi-stable and monostable broadband energy harvesters are entirely new to the literature and are designed and analyzed in the present study. The time response, phase diagram, Poincare map, and bifurcation diagram when the nonlinear system is subjected to ambient harmonic excitation and a nonlinear magnetic force have been employed to understand the system response and the generated power. These investigations are envisaged to provide an insight into the dynamics of these devices and to aid ongoing research associated with their fabrication as well as future design improvements

Cosserat Analysis of Microscale Structures

In this thesis, the application of Cosserat mechanics to micro-scale structures is explored. Different structures considered include micro-scale gyroscopes, micro-cantilevers, and clamped-clamped micro-structures. Two-dimensional formulations with nonlinearities up to third order are derived and presented. Different parameterization schemes are used and the equivalence between the obtained results is discussed. Comparisons with prior results available in the literature are made in terms of inertia properties, stiffness properties, and natural frequencies. The present work points to the importance of considering Cosserat mechanics for examining the motions of micro-scale structures that undergo large as well as coupled deformations