Wireless actuation of bulk acoustic modes in micromechanical resonators

We report wireless actuation of a Lamb wave micromechanical resonator from a distance of over 1 m with an efficiency of over 15%. Wireless actuation of conventional micromechanical resonators can have broad impact in a number of applications from wireless communication and implantable biomedical devices to distributed sensor networks.Financial support from FemtoDx is acknowledged. (FemtoDx)http://nano.bu.edu/Papers_files/Wireless-APL-4961247.pdfPublished versio

Surface Acoustic Wave (SAW) Vibration Sensors

In the paper a feasibility study on the use of surface acoustic wave (SAW) vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit

An Inventive Framework of Micro-Electromechanical System (MEMS)

MEMS is an enabling technology allowing the development of smart products, enhancing the computational ability of microelectronics with the perception and control capabilities of micro sensors and micro actuators and expanding the space of possible designs and applications. MEMS is a relatively new technology which exploits the existing microelectronics infrastructure to create complex machines with micron feature sizes. MEMS promises to revolutionize nearly every product category by bringing together silicon based microelectronics with micro machining technology, making possible the realization of compl ete systems on a chip. Microelectromechanical systems (MEMS) technolog enable us to create various useful sensing and actuating devices integrated with other microelectronic, optoelectronic, microwave, thermal and mechanical devices for advanced Microsystem s. Micromachining and micro electro mechanical systems (MEMS) technologies can be used to produce complex structure, devices, and systems on the scale of micrometers. MEMS products based on piezoelectric and capacitance sensing now include pressure and flo w sensors, accelerometers, gyroscopes, microphones, digital light projectors, oscillators, and RF switches. MEMS devices are used in virtually all areas of industrial activity, health care, consumer products, construction, and milita ry and space hardware. The future of MEMS is multifaceted, complex, and subject to change, in response to the prevailing winds of investment by government and commercial entities. This diversification of product offerings and globalization of the industry has been accompanied by strong revenue growth and growing private investment. Much of the growth in MEMS business is expected to come from products that are in early stages of development or yet to be invented

Bulk Acoustic Wave Accelerometers

Accelerometers and associated techniques for detecting motion are described. For a resonant accelerometer, an externally-applied acceleration can cause a change in the electrical spring constant Ke of the electromechanical system. A resonant accelerometer can be driven to resonate in a bulk acoustic wave mode of vibration, which can have a high resonant frequency. Other accelerometers and associated techniques are disclosed.Georgia Tech Research Corporatio

Bulk Acoustic Wave Accelerometers

Accelerometers and associated techniques for detecting motion are described. For a resonant accelerometer, an externally-applied acceleration can cause a change in the electrical spring constant Kc of the electromechanical system. A resonant accelerometer can be driven to resonate in a bulk acoustic wave mode of vibration, which can have a high resonant frequency. Other accelerometers and associated techniques are disclosed.Georgia Tech Research Corporatio

Выбор материала чувствительных элементов акселерометров на основе ПАВ

Introduction. At the present, sensors based on surface acoustic waves (SAW) is a rapidly developing direction and a promising replacement for classical sensors, especially in those areas where long-term performance of latter is questionable. The principle of operation of SAW sensors is based on acoustic vibrations, therefore, the choice of piezoelectric material of а console, considering external influences on a future device and its operating conditions, is the most important task. Currently, many monocrystalline structures and their sections have been synthesized and created for the devices using SAW. The main materials used for the manufacture of substrates are crystals of quartz (SiO2), lithium niobate (LiNbO3), lithium tantalate (LiTaO3) and film aluminum nitride (AlN). Also, new crystal structures: langasite (La3Ga5SiO14), langatate (La3Ga5.5Ta0.5O14), langanite and others were produced. The problem of using such materials for the manufacture of consoles is the lack of systematized data on important characteristics for the propagation of surfactants, for example, the elasticity tensor of the 4th rank. One of the key problems for the further development of SAW-based sensors is the one-way fastening of rectangular and triangular sensitive elements (SE) in sensor housing. In order to overcome the above drawback an MMA surfactant thing based on a membrane SE for a more uniform distribution of a load over the surface of the SE was proposed.Aim. To show the advantages of using AlN as the SE material of a ring wave resonator on SAW.Materials and methods. The theoretical part of the research was carried out using the finite element method. Mathematical processing was implemented in AutoCAD 2019 and in COMSOL Multiphysics 5.4.Results. The use of AlN, which acts as the SE material for measuring an acceleration based on SAW was proposed. The proposed solution was compared with existing prototypes based on the use of SiO2 / LiNbO3 membranes, which were characterized by strong anisotropic properties. A 3D model of the SE of a ring wave resonator on surface waves was created. Using computer simulations and COMSOL Multiphysics software, it was shown that the thing was capable to withstand exposures in excess of 10 000 g, and an isotropic AlN sensor overcomed the limitations of both the low sensitivity of SiO2 and the low temperature stability of LiNbO3. AlN demonstrated almost double resistance to irreversible mechanical deformations as compared to SiO2, which, in turn, allows an additional 1.5-fold increase in sensitivity compared to quartz – based sensors.Conclusion. Based on the data obtained by the modeling, it can be concluded that the use of AIN as SE material is promising, especially for measuring high acceleration values, but with restrictions on temperature sensitivity of the material.Введение. Датчики на основе поверхностных акустических волн (ПАВ) являются стремительно развивающимся направлением и перспективной заменой классических датчиков, особенно в тех сферах, где длительная работоспособность последних под вопросом. Принцип работы датчиков на ПАВ основан на акустических колебаниях, поэтому выбор пьезоэлектрического материала консоли с учетом внешних влияний на будущее устройство и его условий работы является важнейшей задачей. Синтезировано и создано множество монокристаллических структур и их срезов для устройств на поверхностных акустических волнах. Основными материалами, применяемыми для изготовления подложек, являются кристаллы кварца (SiO2), ниобата лития (LiNbO3), танталата лития (LiTaO3) и пленочный нитрид алюминия (AlN). Производятся новые кристаллические структуры: лангасит (La3Ga5SiO14), лангатат (La3Ga5.5Ta0.5O14), ланганит и др. Проблема применения подобных материалов для изготовления консолей – отсутствие систематизированных данных о важных характеристиках для распространения ПАВ, к примеру тензора упругости 4-го ранга. Чтобы преодолеть указанный недостаток, предложена конструкция микромеханического акселерометра на основе ПАВ, основанного на мембранном ЧЭ для более равномерного распределения нагрузки по поверхности ЧЭ. Одна из ключевых проблем для дальнейшего развития датчиков на основе ПАВ - одностороннее закрепление прямоугольных и треугольных чувствительных элементов (ЧЭ) в корпусе датчика.Цель работы. Показать преимущества использования AlN как материала чувствительного элемента кольцевого волнового резонатора на поверхностных акустических волнах.Материалы и методы. Применение метода конечных элементов и математическая обработка в AutoCAD 2019 и COMSOL Multiphysics 5.4.Результаты. Предложено использовать AlN в качестве материала чувствительного элемента для измерения ускорения на основе ПАВ. Предлагаемое решение сравнивалось с существующими прототипами, основанными на использовании мембран SiO2/LiNbO3, которые характеризуются сильными анизотропными свойствами. Создана 3D-модель ЧЭ кольцевого волнового резонатора на поверхностных волнах. Используя компьютерное моделирование и программное обеспечение COMSOL Multiphysics доказано, что конструкция способна выдерживать воздействия свыше 10 000 g и чувствительный элемент на основе изотропного AlN преодолевает ограничения как низкой чувствительности SiO2, так и малой температурной стабильности LiNbO3. AlN демонстрирует почти двойную устойчивость к необратимым механическим деформациям по сравнению с SiO2, что, в свою очередь, позволяет дополнительно повысить чувствительность в 1.5 раза по сравнению с датчиками на основе кварца.Заключение. Исходя из созданной модели, можно сделать вывод о перспективности использования нитрида алюминия как материала для чувствительного элемента, особенно для измерения больших значений ускорения, но c ограничениями по температурной чувствительности материала

Микроакселерометр на поверхностных акустических волнах с кольцевым резонатором на анизотропном материале

Introduction. Diagnostic systems are designed to monitor the condition of operational components (for example, on the railway). It is imperative that micro-electromechanical systems (MEMS) equipped with acceleration sensors (accelerometers) be used as part of measuring diagnostic systems. It is known that accelerometers are operated under increased vibration and repeated shock loads. This imposes a limitation both on the accelerometer design and the properties of materials from which these devices are produced.Aim. To develop a micromechanical accelerometer (MMA) for surface acoustic waves (SAW), capable of measuring shock effects.Materials and methods. The theoretical part of the study was carried out using the mathematical theory of differential equations, theoretical mechanics, finite element analysis and elements of SAW theory. In the course of the work, the following methods of mathematical processing were applied: MATLAB, Mathcad, Maple, COMSOL Multiphysics, OOFELIE: Multiphysics, Bluehill3 software, CorelDRAW. Experimental studies were also conducted using the INSTRON 5985 floor automated test system.Results. An original design of MMA on a SAW capable of measuring shock effects in hundreds of g was proposed. A sensing element (SE) of the sensor was developed. An analysis of the plate materials for their use as part of the SAW-based MMA design showed that SE from the quartz ST-cut material has a wider range of measured accelerations and a higher sensitivity threshold than SE from the YX-128˚ cut-off lithium niobate material. Requirements were developed to increase the SE sensitivity threshold. Design requirements were developed, and an interdigital transducer (IDT) topology in the form of a ring resonator was proposed. The following output characteristics were assessed: sensitivity threshold, dynamic range and scale factor. In addition, a procedure was developed for calculating MMA on a SAW with a ring resonator on an anisotropic material. It was found that the developed SE is characterized by a high sensitivity threshold, a wide dynamic range and a low transverse sensitivity.Conclusion. The technique proposed for designing a sensing element for use in solid-state linear acceleration sensors facilitates, depending on technical requirements, selection of construction materials and sensor design. Due to the originality of the design and engineering solutions, the proposed accelerometer allows measurements to be carried out across a wide range of impact loads.Введение. Состояние объектов эксплуатации (например, на железной дороге) контролируется системами диагностики. В их составе используются микроэлектромеханические системы, комплектуемые датчиками ускорения (акселерометрами). В процессе эксплуатации акселерометры подвергаются значительным вибрациям и многократно повторяющимся ударным воздействиям. Это накладывает ограничения на конструкцию и материалы, из которых изготавливаются акселерометры.Цель работы. Разработка микромеханического акселерометра (ММА) на поверхностных акустических волнах (ПАВ), способного измерять ударные воздействия.Материалы и методы. Теоретическая часть работы выполнялась с применением математической теории дифференциальных уравнений, теоретической механики, конечно-элементарного анализа и элементов теории ПАВ. В ходе работы применялась математическая обработка в программах MATLAB, Mathcad, Maple, COMSOL Multiphysics, OOFELIE::Multiphysics, ПО Bluehill3, CorelDRAW. Экспериментальные исследования проведены с привлечением напольной автоматизированной испытательной системы INSTRON 5985.Результаты. Разработана концепция построения и предложена оригинальная конструкция ММА на ПАВ, способного измерять ударные воздействия в сотни g. Разработан чувствительный элемент (ЧЭ) сенсора. Анализ материалов для пластин в составе конструкции ММА на ПАВ показал, что ЧЭ из кварца ST-среза отличается более широким диапазоном измеряемых ускорений и более высоким порогом чувствительности, чем ЧЭ из ниобата лития среза YX-128°. Выработаны требования и исследована возможность повышения порога чувствительности датчика. Сформулированы требования к проектированию и предложена топология встречно-штыревого преобразователя (ВШП) в виде кольцевого резонатора. Предложена оригинальная топология резонатора с неэквидистантным ВШП для учета анизотропии материала чувствительного элемента. Оценены выходные характеристики: порог чувствительности, динамический диапазон, масштабный коэффициент. Предложена методика расчета ММА на ПАВ с кольцевым резонатором на анизотропном материале. ЧЭ ММА такой конструкции имеет высокий порог чувствительности, широкий динамический диапазон и малую поперечную чувствительность.Заключение. Предложенная методика проектирования ЧЭ твердотельного датчика линейных ускорений позволяет выбрать материал и систему съема измерительной информации в зависимости от технических требований. Благодаря оригинальности конструкторско-технологического решения предложенный акселерометр позволяет проводить измерения в широком диапазоне ударных воздействий

Design and micro-fabrication of tantalum silicide cantilever beam threshold accelerometer

Microfabricated threshold accelerometers were successfully designed and fabricated following a careful analysis of the electrical, mechanical, and fabrication issues inherent to micron-sized accelerometers. A uniform cantilever beam was chosen because of the simplicity of design and fabrication. New models for the electrostatic force exerted on the cantilever beam were developed and calculations were made that accurately predicted the electrical characteristics of the accelerometer. The calculations also provided design guidelines for optimizing the accelerometer dimensions. Computer simulation demonstrated that the error of the electrostatic force, calculated using the most accurate model, was within 2% of the actual force which was obtained by integrating the closed formula, through the bent beam curvature, for device parameters designed to detect an acceleration of 50 g. Conversely, it was shown that the widely used conventional parallel plate model had an error of approximately 90%. Novel surface micromachining process steps were successfully developed to fabricate the cantilever beam accelerometers. Sputter deposited tantalum silicide and commercially available spin-on-glass were used as a structural layer and a sacrificial layer, respectively. The dependence of resistivity, crystalline structure, Young\u27s modulus, and hardness of the tantalum silicide films on the annealing temperatures were measured. These results were employed to design accelerometers that were successfully operated. Excluding the metallization steps, only two masks and four photolithography steps were required. However, both positive and negative photoresists had to be utilized. NJIT\u27s standard photolithography steps were used for positive photoresist; however for the negative photoresist a specially developed multi-puddle process was used to obtain 4 micron resolution. Electrostatic attraction tests, of accelerometers, were performed using the Keithley current-voltage measurement system. These tests used deflection voltages ranging from 2.2 to 37.0 volts, corresponding to threshold acceleration levels from 580 to 18,500 g. Nearly 70 percent of the threshold voltage results fell within the expected error limits set by the accuracy of the device dimensions when processing tolerances were taken into account including the thickness variation caused by 8% uncertainty in the buffered HF etch rate of tantalum silicide. Some accelerometers were closed and opened 3 times without failure. The accelerometers tended to break after 3 times of operation and this was attributed to the welding of contacts. Centrifuge acceleration tests of accelerometers were carried out in a specially designed centrifuge in an acceleration range of 282 to 11,200 g. Nearly 80 percent of the threshold acceleration results fell within the expected error limits set by the accuracy of the device dimensions when processing tolerances were taken into account

Development and experimental analysis of a micromachined Resonant Gyrocope

This thesis is concerned with the development and experimental analysis of a resonant gyroscope. Initially, this involved the development of a fabrication process suitable for the construction of metallic microstructures, employing a combination of nickel electroforming and sacrificial layer techniques to realise free-standing and self-supporting mechanical elements. This was undertaken and achieved. Simple beam elements of typically 2.7mm x 1mm x 40µm dimensions have been constructed and subject to analysis using laser doppler interferometry. This analysis tool was used to implement a fill modal analysis in order to experimentally derive dynamic parameters. The characteristic resonance frequencies of these cantilevers have been measured, with 3.14kHz, 23.79kHz, 37.94kHz and 71.22kHz being the typical frequencies of the first four resonant modes. Q-factors of 912, 532, 1490 and 752 have been measured for these modes respectively at 0.01mbar ambient pressure. Additionally the mode shapes of each resonance was derived experimentally and found to be in excellent agreement with finite element predictions. A 4mm nickel ring gyroscope structure has been constructed and analysed using both optical analysis tools and electrical techniques. Using laser doppler interferometry the first four out-of-plane modes of the ring structure were found to be typically 9.893 kHz, 11.349 kHz, 11.418 kHz and 13.904 kHz with respective Q-factors of 1151, 1659, 1573 and 1407 at 0.01 mbar ambient pressure. Although electrical measurements were found to be obscured through cross coupling between drive and detection circuitry, the in-plane operational modes of the gyroscope were sucessfully determined. The Cos2Ө and Sin2Ө operational modes were measured at 36.141 kHz and 36.346 kHz, highlighting a frequency split of 205kHz. Again all experimentally derived modal parameters were in good agreement with finite element predictions. Furthermore, using the analysis model, the angular resolution of the gyroscope has been predicted to be approximately 4.75º/s

Nonlinear mechanics and nonlinear material properties in micromechanical resonators

Microelectromechanical Systems are ubiquitous in modern technology, with applications ranging from accelerometers in smartphones to ultra-high precision motion stages used for atomically-precise positioning. With the appropriate selection of materials and device design, MEMS resonators with ultra-high quality factors can be fabricated at minimal cost. As the sizes of such resonators decrease, however, their mechanical, electrical, and material properties can no longer be treated as linear, as can be done for larger-scale devices. Unfortunately, adding nonlinear effects to a system changes its dynamics from exactly-solvable to only solvable in specific cases, if at all. Despite (and because of) these added complications, nonlinear effects open up an entirely new world of behaviors that can be measured or taken advantage of to create even more advanced technologies. In our resonators, oscillations are induced and measured using aluminum nitride transducers. I used this mechanism for several separate highly-sensitive experiments. In the first, I demonstrate the incredible sensitivity of these resonators by actuating a mechanical resonant mode using only the force generated by the radiation pressure of a laser at room temperature. In the following three experiments, which use similar mechanisms, I demonstrate information transfer and force measurements by taking advantage of the nonlinear behavior of the resonators. When nonlinear resonators are strongly driven, they exhibit sum and difference frequency generation, in which a large carrier signal can be mixed with a much smaller modulation to produce signals at sum and difference frequencies of the two signals. These sum and difference signals are used to detect information encoded in the modulation signal using optical radiation pressure and acoustic pressure waves. Finally, in my experiments, I probe the nonlinear nature of the piezoelectric material rather than take advantage of the nonlinear resonator behavior. The relative sizes of the linear and nonlinear portions of the piezoelectric constant can be determined because the force applied to the resonator by a transducer is independent of the dielectric constant. This method allowed me to quantify the nonlinear constants