A three-axis accelerometer for measuring heart wall motion

This thesis presents the work carried out in the design, simulation, fabrication and testing of miniaturised three-axis accelerometers. The work was carried out at the Faculty of Science and Engineering at Vestfold University College (Tønsberg, Norway), the MIcroSystems Engineering Centre (MISEC) at Heriot-Watt University and in collaboration with the Interventional Centre at Rikshospitalet University Hospital (Oslo, Norway). The accelerometers presented in this thesis were produced to be stitched to the surface of human hearts. In doing so they are used to measure the heart wall motion of patients that have just undergone heart bypass surgery. Results from studies carried out are presented and prove the concept of using such sensors for the detection of problems that can lead to the failure of heart bypasses. These studies were made possible using commercially available MEMS (MicroElectroMechanical Systems) three-axis accelerometers. However, the overall size of these sensors does not meet the requirements deemed necessary by the medical team (2(W) 2(H) 5(L) mm3) and fabrication activities were necessary to produce custom-made sensors. Design verification and performance modelling were carried out using Finite Element Analysis (FEA) and these results are presented alongside relevant analytical calculations. For fabrication, accelerometer designs were submitted to three foundry processes during the course of the work. The designs utilise the piezoresistive effect for the acceleration sensing and fabrication was carried out by bulk micromachining. Results of the characterisaton of the sensors are presente

MEMS Accelerometers

Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc

Contribution au micro-actionnement multi-stable piloté par radiations optiques

In this work, a bistable mechanism based on antagonistic pre-shaped double beams was proposed. Employing the proposed bistable mechanism, a quadristable micro-actuator was designed. ln order to validate the quadristability of the device, a meso-scaled prototype was fabricated from MDF by laser cutting. After the quadristability was experimentally confirmed, a quadristable micro-actuator was realized on SOl wafer using DRIE technique. Strokes for inner row and outer row were reduced to 300 µm and 200 µm respectively. For the actuation of the quadristable micro-actuator,laser heated SMA elements with deposited Si02 layer were used to realize the optical wireless actuation. With the help of a laser beam steering micro-mirror, both inner row and outer row were successfully actuated. ln order to further reduce the stroke, a bistable actuator with stroke reducing structure was designed and a prototype eut from MDF was tested. Bistability was validated and a stroke of 1µm was experimentally achieved. Based on this bistable module, a multistable nano-actuator, which contains four parallel coupled bistable modules,was designed and simulated. The simulated result have indicated that it was capable of outputs 16 discrete stable positions available from 0 nm to 150 nm with a step of 10 nm between two stable positions.Cette thèse traite le sujet du micro-actionnement multistable employant des radiations optiques pour atteindre les différentes positions offertes par le micro-actionneur. Dans le cadre des travaux réalisés, un mécanisme bistable reposant sur un principe de doubles poutres préformées situées en position antagoniste est proposé, et, sur cette brique élémentaire, un micro-actionneur quadristable a été conçu. Afin de valider le principe de fonctionnement de micro-actionneur, des procédés de fabrication Laser (sur le matériau « médium - MDF») puis DRIE (sur un wafer SOI de silicium) ont été utilisés. Sur le prototype en silicium, permettant une réduction des courses du rang interne et du rang externe du micro-actionneur, celles-ci ont été fixées à 300 µm et 200 µm respectivement. L’actionnement à distance de ce micro-actionneur a été prouvé en utilisant le chauffage laser d’un élément actif en Nitinol structuré par un dépôt de SiO2, ceci générant un effet « deux sens » de l’élément actif permettant d’annuler la charge sur les poutres du micro-actionneur une fois celui-ci déclenché puis en position stable. L’utilisation d’un banc expérimental incluant une membrane MEMS de balayage laser a permis de démontrer la quadristabilité du micro-actionneur sur 90 000 cycles. Afin de réduire davantage la course de ce micro-actionneur, des concepts de dispositifs de réduction de course ont été développés pour démontrer, à partir de prototypes fabriqué en MDF par usinage laser, la capacité à atteindre une course de 1 µm. Enfin, à la suite de ces travaux de réduction de course, un concept de nano-actionneur multistable a été proposé. Ce nano-actionneur est composé de quatre modules bistables liés et disposés en parallèle pour offrir 16 positions discrètes sur une course rectiligne. Les simulations de cet actionneur montrent la possibilité d’atteindre les 15 positions espacées de 10 nm sur une course de 150 nm

EUROSENSORS XVII : book of abstracts

Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)

Micro/Nano Structures and Systems

Micro/Nano Structures and Systems: Analysis, Design, Manufacturing, and Reliability is a comprehensive guide that explores the various aspects of micro- and nanostructures and systems. From analysis and design to manufacturing and reliability, this reprint provides a thorough understanding of the latest methods and techniques used in the field. With an emphasis on modern computational and analytical methods and their integration with experimental techniques, this reprint is an invaluable resource for researchers and engineers working in the field of micro- and nanosystems, including micromachines, additive manufacturing at the microscale, micro/nano-electromechanical systems, and more. Written by leading experts in the field, this reprint offers a complete understanding of the physical and mechanical behavior of micro- and nanostructures, making it an essential reference for professionals in this field

Optical Fiber Interferometric Sensors

The contributions presented in this book series portray the advances of the research in the field of interferometric photonic technology and its novel applications. The wide scope explored by the range of different contributions intends to provide a synopsis of the current research trends and the state of the art in this field, covering recent technological improvements, new production methodologies and emerging applications, for researchers coming from different fields of science and industry. The manuscripts published in the Special issue, and re-printed in this book series, report on topics that range from interferometric sensors for thickness and dynamic displacement measurement, up to pulse wave and spirometry applications

Design and fabrication of a multipurpose compliant nanopositioning architecture

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 227-241).This research focused on generating the knowledge required to design and fabricate a high-speed application flexible, low average cost multipurpose compliant nanopositioner architecture with high performance integrated sensing. Customized nanopositioner designs can be created in ~~1 week, for 30x increase in sensing dynamic range over comparable state-of-the-art compliant nanopositioners. These improvements will remove one of the main hurdles to practical non-IC nanomanufacturing, which could enable advances in a range of fields including personalized medication, computing and data storage, and energy generation/storage through the manufacture of metamaterials. Advances were made in two avenues: flexibility and affordability. The fundamental advance in flexibility is the use of a new approach to modeling the nanopositioner and sensors as combined mechanical/electronic systems. This enabled the discovery of the operational regimes and design rules needed to maximize performance, making it possible to rapidly redesign nanopositioner architecture for varying functional requirements such as range, resolution and force. The fundamental advance to increase affordability is the invention of Non-Lithographically-Based Microfabrication (NLBM), a hybrid macro-/micro-fabrication process chain that can produce MEMS with integrated sensing in a flexible manner, at small volumes and with low per-device costs. This will allow for low-cost customizable nanopositioning architectures with integrated position sensing to be created for a range of micro-/nano- manufacturing and metrology applications. A Hexflex 6DOF nanopositioner with titanium flexures and integrated siliconpiezoresistive sensing was fabricated using NLBM. This device was designed with a metal mechanical structure in order to improve its robustness for general handling and operation. Single crystalline silicon piezoresistors were patterned from bulk silicon wafers and transferred to the mechanical structure via thin-film patterning and transfer. This work demonstrates that it is now feasible to design and create a customized positioner for each nanomanufacturing/metrology application. The Hexflex architecture can be significantly varied to adjust range, resolution, force scale, stiffness, and DOF all as needed. The NLBM process was shown to enable alignment of device components on the scale of 10's of microns. 150μm piezoresistor arm widths were demonstrated, with suggestions made for how to reach the expected lower bound of 25[mu]m. Flexures of 150[mu]m and 600[mu]m were demonstrated on 4 the mechanical structure, with a lower bound of ~~50[mu]m expected for the process. Electrical traces of 800[mu]m width were used to ensure low resistance, with a lower bound of ~~100[mu]m expected for the process. The integrated piezoresistive sensing was designed to have a gage factor of about 125, but was reduced to about 70 due to lower substrate temperatures during soldering, as predicted by design theory. The sensors were measured to have a full noise dynamic range of about 59dB over a 10kHz sensor bandwidth, limited by the Schottky barrier noise. Several simple methods are suggested for boosting the performance to ~~135dB over a 10kHz sensor bandwidth, about a <1Å resolution over the 200[mu]m range of the case study device. This sensor performance is generally in excess of presently available kHz-bandwidth analog-to-digital converters.by Robert M. Panas.Ph.D