Thin-Film PZT Scanning Micro-actuators for Vertical Cross-sectional Imaging in Endomicroscopy

The advancement of optics and the development of microelectromechanical systems (MEMS) based scanners has enabled powerful optical imaging techniques that can perform optical sectioning with high resolution and contrast, large field of view, and long working distance to be realized in endoscope-compatible form factors. Optical endomicroscopes based on these imaging techniques can be used to obtain in vivo vertical cross-sectional images of dysplastic tissues in the hollow organs before they progress to mucosal diseases such as colorectal cancer. However, existing endomicroscopic systems that use imaging modalities compatible with the use of fluorescent biomarkers are not capable of deep vertical sectioning in real time. This work proposes a unique MEMS-based scanning mechanism to be incorporated into endoscopic microscopes for real-time in vivo deep into-tissue scanning for early cancer detection. For this task, a class of novel multi-axis micro-scanners based on thin-film lead-zirconate-titanate (PZT) has been developed. Leveraging the large piezoelectric strain coefficient of PZT, the prototypes have demonstrated more than 400 μm of out-of-plane displacement with bandwidths on the order of 100-200 Hz in only a 3.2 mm-by-3.2 mm footprint, which meets the requirements for this application. The scanners have a central rectangular-shaped reflector, whose corners are supported by four symmetric PZT bending legs that generate vertical translation. This design gives the reflector a three-axis motion. The challenges to fabricate high performance piezoelectric actuators are discussed with device failure mechanisms observed during the fabrication of the 1st generation scanners. Improved fabrication steps are presented that solve the issues with the 1st generation devices and enhance the robustness of the scanners for instrument integration. Remaining non-ideal fabrication outcomes cause MEMS devices to produce unwanted motions, which can degrade imaging quality. To overcome this problem, a method to drive MEMS actuators having multiple vibration modes with close frequencies to produce a desired motion pattern with a single input is presented, and was used to generate a pure vertical motion for imaging. Two-photon based vertical cross-sectional images of mouse colon was obtained in real time for the first time using a thin-film piezoelectric microscanner. To understand the effects of fabrication non-idealities on the device behavior and produce more robust scanner performance, analytical models that describes large vertical and rotational motions including multi-axis coupling were developed. A static model that was initially developed for design optimization was calibrated, along with a transient model, using experimental data to incorporate the effects of dimensional variations and residual stress. This models can be used with future integrated sensors and feedback controllers for more precise and robust motion of the scanner. This calibration technique can be useful in developing analytic models for MEMS devices subject to fabrication uncertainty. In addition, nonlinear dynamic behavior due to large vertical stroke in the presence of fabrication non-idealities is captured by linearizing an expanded dynamic model about different static positions obtained by numerically solving the expanded nonlinear model.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137124/1/jongs_1.pd

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

Design of a high-speed-force-stroke thermomechanical micro-actuator via geometric contouring and mechanical frequency multiplication

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 187-192).The aims of this research were to understand (1) why marked performance improvements are observed when one contours the geometry of micro-thermomechanical actuators (pTMAs), (2) how to parametrically model and optimize these improvements, (3) how to use transient electrical command signals to augment these improvements, and (4) how to design arrayed pairs of actuator teams that enable the realization of these improvements within small-scale precision machines. This work has extended the performance envelope of small-scale electromechanical systems to cover the needs of emerging positioning applications that were previously impractical. The results are important to, for example, small-scale machines that are increasingly needed within biological imaging equipment, equipment for nanomanufacturing, and instruments for nano-scale research. These positioning systems must be of small geometric scale in order to achieve viable bandwidth (kHz), resolution (nanometers), cost ($10s/device) and stability (A/min) levels. Miniaturized machines require small-scale actuators, but unfortunately, state-of-the-art actuators are not capable of simultaneously satisfying the force (~10OmN), stroke (~100pLm) and bandwidth (-lkHz) requirements of the preceding applications. In the absence of a practical actuation technology, many small-scale devices were relegated to "demo" status, and they never realized the full promise that small-scale machines could deliver for the preceding applications. This work has generated two concepts - geometric contouring and mechanical frequency multiplication that make jtTMAs behave in a manner that is very different from how they have acted in the past: (1) Geometric contouring:(cont) The variation of a beam's cross-sectional area along its length to achieve more favorable thermal characteristics, i.e. temperature profile, while simultaneously reducing the elastic energy storage within the beam, and (2) Mechanical frequency multiplication: The use of pTMAs pairs that cooperate to reduce their combined cycle time below their individual cycle times, thereby increasing their operating frequency. The utility and practical implementation of these techniques were illustrated via a case study on a threeaxis optical scanner for a two-photon endomicroscope. The device consisted of three sub-systems: (i) an optical system (prism, graded index lens, and optical fiber) that was used to deliver/collect photons during imaging, (ii) a small-scale electromechanical scanner that could raster scan the focal point of the optics through a specimen and (iii) a silicon optical bench that connects the electromechanical and optical systems. The scanner was required to fit within a 7mm 0 endoscope port and scan at 1kHz throughout a 100xl00xl00 IPn3 volume. The results of this thesis were used to engineer a scanner that was capable of 3.5kHz x 100Hz x 30Hz scanning throughout a 125 x 200 x 200 jtm3 volume. Preceding jtTMA technology could only scan over 12.5% of the required volume at 10% of the required frequency. This work forms a body of knowledge - design rules, principles and best practices - that may be used to realize similar benefits in other small-scale devices.by Shih-Chi Chen.Ph.D

Optical MEMS

Optical microelectromechanical systems (MEMS), microoptoelectromechanical systems (MOEMS), or optical microsystems are devices or systems that interact with light through actuation or sensing at a micro- or millimeter scale. Optical MEMS have had enormous commercial success in projectors, displays, and fiberoptic communications. The best-known example is Texas Instruments’ digital micromirror devices (DMDs). The development of optical MEMS was impeded seriously by the Telecom Bubble in 2000. Fortunately, DMDs grew their market size even in that economy downturn. Meanwhile, in the last one and half decade, the optical MEMS market has been slowly but steadily recovering. During this time, the major technological change was the shift of thin-film polysilicon microstructures to single-crystal–silicon microsructures. Especially in the last few years, cloud data centers are demanding large-port optical cross connects (OXCs) and autonomous driving looks for miniature LiDAR, and virtual reality/augmented reality (VR/AR) demands tiny optical scanners. This is a new wave of opportunities for optical MEMS. Furthermore, several research institutes around the world have been developing MOEMS devices for extreme applications (very fine tailoring of light beam in terms of phase, intensity, or wavelength) and/or extreme environments (vacuum, cryogenic temperatures) for many years. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on (1) novel design, fabrication, control, and modeling of optical MEMS devices based on all kinds of actuation/sensing mechanisms; and (2) new developments of applying optical MEMS devices of any kind in consumer electronics, optical communications, industry, biology, medicine, agriculture, physics, astronomy, space, or defense

Multi-spectral Dual Axes Confocal Endomicroscope with Vertical Cross-sectional Scanning for In-vivo Targeted Imaging of Colorectal Cancer

Pathologists review histology cut perpendicular to the tissue surface or in the vertical cross-section (XZ-plane) in order to visualize the normal or abnormal differentiation patterns. The epithelium of hollow organs, such as the colon, is the origin of many important forms of cancer. The vertical cross-section provides a comprehensive view of the epithelium which normally differentiates in the basilar to luminal direction. Real-time imaging in this orientation has not been fully explored in endomicroscopy because most instruments collect images in the horizontal cross-section (XY-plane). Imaging microstructures from the tissue surface to about half a millimeter deep can reveal early signs of disease. Furthermore, the use of molecular probes is an important, emerging direction in diagnostic imaging that improves specificity for disease detection and reveals biological function. Dysplasia is a pre-malignant condition in the colon that can progress into colorectal cancer. Peptides have demonstrated tremendous potential for in-vivo use to detect colonic dysplasia. Moreover, peptides can be labeled with NIR dyes for visualizing the full depth of the epithelium in small animals. This study aims to demonstrate large FOV multi-spectral targeted in-vivo vertical optical section with a dual axes confocal endomicroscope enabled by MEMS technology. The NIR multi-spectral fluorescence images demonstrate both histology-like morphology imaging and molecular imaging of specific peptide binding to dysplasia in the mouse colon. The specific aims of this study are: (1) to develop miniature vertical cross-sectional scan engine based on MEMS technology for imaging on XZ-plane; (2) to integrate micro-optics and develop multi-spectral dual axes confocal endomicroscope imaging system; (3) to perform in-vivo targeted vertical cross-sectional imaging with large FOV on colorectal cancer mouse model.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107154/1/zqiu_1.pd

Modellbasierter Systementwurf zur Steuerung und Regelung quasi-statischer Mikroscannerspiegel mit elektrostatischem Kammantrieb

Aus einkristallinem Silizium gefertigte Mikroscanner werden zunehmend in Anwendungen zur Bildprojektion, Entfernungssensorik, Spektroskopie und gezielten Strahlführung von Lasern eingesetzt, denn sie ermöglichen die Miniaturisierung und Massenfertigung optischer Systeme. Durch die statische Strahlpositionierung und zum linearen Rasterscannen in einem breiten Frequenzbereich von Null bis mehrere hundert Hertz eröffnen sogenannte quasi-statische Mikroscanner im Vergleich zu bisherigen resonant schwingenden Mikroscannern ein deutlich breiteres und flexibleres Anwendungsspektrum. Jedoch wird die Bewegung aufgrund der extrem geringen Dämpfung des Systems mit Eigenschwingungen überlagert. Daher ist die Steuerung und Regelung eine notwendige Voraussetzung für die hochdynamische und präzise Strahlführung mit quasi-statischen Mikroscannern. In dieser Arbeit werden verschiedene Steuerungs- und Regelungskonzepte für quasi-statische Mikroscanner mit elektrostatischem Kammantrieb entworfen und auf einem Echtzeitsystem mit optischer Rückführung experimentell verifiziert. Das nichtlineare mechatronische Modell wird vollständig parametrisiert und geeignete Trajektorien mit Ruckbegrenzung werden hergeleitet. Schließlich werden die Regelung des Mikroscanners mit einem Mikrocontroller durch die im Chip integrierte piezoresistive Positi-nssensorik validiert und ein 2D-Rasterscan realisiert. Als Ergebnis werden Folgerungen für den Systementwurf von quasi-statischen Mikroscannern abgeleitet.:Kurzfassung Abstract Inhaltsverzeichnis Abbildungs- und Tabellenverzeichnis Abkürzungs- und Symbolverzeichnis 1 Einleitung 1.1 Anwendungsgebiete 1.2 Antriebsprinzipien für Mikroscanner 1.3 Quasi-statische Mikroscanner des Fraunhofer IPMS 1.4 Mechatronische Modellbildung 1.4.1 Elektrostatischer Elementarwandler 1.4.2 Mechanische Beschaltung 1.4.3 Impedanzrückkopplung 2 Stand der Technik und eigene Beiträge 2.1 Steuerungs- und regelungstechnische Aspekte 2.1.1 Steuerung 2.1.2 Regelung 2.2 Präzisierung der Aufgabenstellung 2.3 Problemstellungen und eigene Beiträge 3 Modellbildung 3.1 Physikalische Modellbildung 3.1.1 Elektrisches Teilsystem 3.1.2 Mechanisches Teilsystem 3.1.3 Mechatronischer Wandler 3.2 Regelungstechnische Modellbildung 3.2.1 Kleinsignalmodell 3.2.2 Zustandsraummodell und Flachheit 3.3 Experimentelle Modellbildung 3.3.1 Bestimmung der Federsteifigkeit und der Dämpfung 3.3.2 Bestimmung der Kapazitätskennlinien 3.4 Schlussfolgerungen 4 Trajektorienentwurf 4.1 Anforderungen 4.1.1 FOURIER-Zerlegung von Dreieck- und Sägezahnfunktion 4.1.2 Überlagerung mit der Streckendynamik 4.2 Ruckbegrenzung 4.2.1 Stufentrajektorie 4.2.2 Dreieck- und Sägezahntrajektorien 4.3 Entwurf mit Regelreserve 4.3.1 Aktuationsbereich 4.3.2 Regelreserve 4.4 Schlussfolgerungen 5 Steuerungs- und Regelungsentwurf 5.1 Steuerung 5.1.1 Statische Steuerung 5.1.2 Vorfilter 5.1.3 Flachheitsbasierte Vorsteuerung 5.1.4 Simulationsergebnisse 5.1.5 Fazit 5.2 Vorauswahl geeigneter Regelungsalgorithmen 5.3 Lineare Regelung 5.3.1 Robuster PID-Regler 5.3.2 Gain-Scheduling-Regler 5.4 Nichtlineare Regelung 5.4.1 Flachheitsbasierte Regelung 5.4.2 Gleitzustandsregelung 5.4.3 Beobachterentwurf 5.4.4 Flachheitsbasierte Vorsteuerung mit Ausgangsstabilisierung 5.4.5 Fazit 5.5 Repetitive Regelung 5.5.1 Dimensionierung des Stabilitätsfilters 5.5.2 Dimensionierung des Lernfilters 5.5.3 Entwurf im linearen und nichtlinearen Regelkreis 5.6 Simulative Verifikation der Regelungsalgorithmen 5.6.1 Simulationsmodell 5.6.2 Simulationsergebnisse 5.6.3 Reglerparametrierung 5.6.4 Regelfrequenzvariation 5.6.5 Variation der Modellparameter 5.6.6 Einfluss von Messrauschen 5.7 Schlussfolgerungen 6 Experimentelle Systemverifikation und Diskussion 6.1 Messaufbau mit Echtzeitsystem 6.1.1 Messaufbau 6.1.2 Echtzeitsystem 6.1.3 Auswertung des optischen Positionsdetektors 6.2 Experimentelle Ergebnisse mit Echtzeitsystem 6.2.1 Fehlerdefinition 6.2.2 Modellverifikation 6.2.3 Ergebnisse der Steuerungsverfahren 6.2.4 Ergebnisse der Regelungsverfahren 6.3 Regelung mit Mikrocontroller 6.3.1 Mikrocontroller und Treiberelektronik 6.3.2 Integrierte piezoresistive Positionssensorik 6.3.3 Regelungsergebnisse mit Mikrocontroller 6.4 Zusammenfassende Diskussion der Ergebnisse 7 Folgerungen für den Systementwurf 7.1 Entwurfsraum 7.1.1 Dynamische Deformation 7.1.2 Stabilitätsspannung 7.1.3 Trajektorienentwurfsraum 7.2 Einsatz der Steuerung und Regelung 7.3 Varianten der Kammanordnung 8 Zusammenfassung 8.1 Erreichte Ziele 8.2 Ausblick 8.3 Abschlussfazit Literaturverzeichnis Publikationen Anhang A Modellbildung und Simulation A.1 Elemente der strukturierten Analyse A.2 Grundlagen der Elektrostatik A.3 Ausführlicher Lagrange-Formalismus A.3.1 Q-Koordinaten A.3.2 PSI-Koordinaten A.4 Kapazitätskennlinien A.5 Impedanzrückkopplung A.6 Mikroscannerparameter A.7 Regelparameter der Simulation A.8 Stabilitätsnachweis der flachheitsbasierter Vorsteuerung mit Ausgangsstabilisierung Anhang B Experimentelle Verifikation B.1 Regelparameter der Messung B.2 Spannungs- und Winkelbeschleunigungsverläufe B.3 Ergebnisse der repetitiven Regelung mit Sägezahntrajektorie B.4 Impedanzmessung der Kammkapazitäten B.5 Geräteliste ThesenMonocrystalline silicon microscanners are increasingly used in applications for image projection, distance sensors, spectroscopy and laser beam control, because they allow the miniaturization and mass production of optical systems. With static beam positioning and linear raster scanning abilities in a wide range of zero to several hundred hertz the so-called quasi-static microscanners offer a much broader and more flexible range of applications compared to common resonantly oscillating microscanners. However, the movement is superimposed with natural oscillations due to the extremely low system damping. Therefore, an open-loop and closed-loop control is necessary for highly dynamic and accurate beam control with quasi-static microscanners. In this thesis different concepts for open-loop and closed-loop control of quasi-static microscanners with electrostatic comb drives are designed and verified experimentally on a real-time system with optical feedback. The nonlinear mechatronic model becomes completely parameterized and suitable trajectories with jerk limitation are derived. The control of the microscanner on a microcontroller with feedback by the on-chip inte-rated piezoresistive position sensors is validated realizing a 2D raster scan. As a result, conclusions for the system design are derived for quasi-static microscanners.:Kurzfassung Abstract Inhaltsverzeichnis Abbildungs- und Tabellenverzeichnis Abkürzungs- und Symbolverzeichnis 1 Einleitung 1.1 Anwendungsgebiete 1.2 Antriebsprinzipien für Mikroscanner 1.3 Quasi-statische Mikroscanner des Fraunhofer IPMS 1.4 Mechatronische Modellbildung 1.4.1 Elektrostatischer Elementarwandler 1.4.2 Mechanische Beschaltung 1.4.3 Impedanzrückkopplung 2 Stand der Technik und eigene Beiträge 2.1 Steuerungs- und regelungstechnische Aspekte 2.1.1 Steuerung 2.1.2 Regelung 2.2 Präzisierung der Aufgabenstellung 2.3 Problemstellungen und eigene Beiträge 3 Modellbildung 3.1 Physikalische Modellbildung 3.1.1 Elektrisches Teilsystem 3.1.2 Mechanisches Teilsystem 3.1.3 Mechatronischer Wandler 3.2 Regelungstechnische Modellbildung 3.2.1 Kleinsignalmodell 3.2.2 Zustandsraummodell und Flachheit 3.3 Experimentelle Modellbildung 3.3.1 Bestimmung der Federsteifigkeit und der Dämpfung 3.3.2 Bestimmung der Kapazitätskennlinien 3.4 Schlussfolgerungen 4 Trajektorienentwurf 4.1 Anforderungen 4.1.1 FOURIER-Zerlegung von Dreieck- und Sägezahnfunktion 4.1.2 Überlagerung mit der Streckendynamik 4.2 Ruckbegrenzung 4.2.1 Stufentrajektorie 4.2.2 Dreieck- und Sägezahntrajektorien 4.3 Entwurf mit Regelreserve 4.3.1 Aktuationsbereich 4.3.2 Regelreserve 4.4 Schlussfolgerungen 5 Steuerungs- und Regelungsentwurf 5.1 Steuerung 5.1.1 Statische Steuerung 5.1.2 Vorfilter 5.1.3 Flachheitsbasierte Vorsteuerung 5.1.4 Simulationsergebnisse 5.1.5 Fazit 5.2 Vorauswahl geeigneter Regelungsalgorithmen 5.3 Lineare Regelung 5.3.1 Robuster PID-Regler 5.3.2 Gain-Scheduling-Regler 5.4 Nichtlineare Regelung 5.4.1 Flachheitsbasierte Regelung 5.4.2 Gleitzustandsregelung 5.4.3 Beobachterentwurf 5.4.4 Flachheitsbasierte Vorsteuerung mit Ausgangsstabilisierung 5.4.5 Fazit 5.5 Repetitive Regelung 5.5.1 Dimensionierung des Stabilitätsfilters 5.5.2 Dimensionierung des Lernfilters 5.5.3 Entwurf im linearen und nichtlinearen Regelkreis 5.6 Simulative Verifikation der Regelungsalgorithmen 5.6.1 Simulationsmodell 5.6.2 Simulationsergebnisse 5.6.3 Reglerparametrierung 5.6.4 Regelfrequenzvariation 5.6.5 Variation der Modellparameter 5.6.6 Einfluss von Messrauschen 5.7 Schlussfolgerungen 6 Experimentelle Systemverifikation und Diskussion 6.1 Messaufbau mit Echtzeitsystem 6.1.1 Messaufbau 6.1.2 Echtzeitsystem 6.1.3 Auswertung des optischen Positionsdetektors 6.2 Experimentelle Ergebnisse mit Echtzeitsystem 6.2.1 Fehlerdefinition 6.2.2 Modellverifikation 6.2.3 Ergebnisse der Steuerungsverfahren 6.2.4 Ergebnisse der Regelungsverfahren 6.3 Regelung mit Mikrocontroller 6.3.1 Mikrocontroller und Treiberelektronik 6.3.2 Integrierte piezoresistive Positionssensorik 6.3.3 Regelungsergebnisse mit Mikrocontroller 6.4 Zusammenfassende Diskussion der Ergebnisse 7 Folgerungen für den Systementwurf 7.1 Entwurfsraum 7.1.1 Dynamische Deformation 7.1.2 Stabilitätsspannung 7.1.3 Trajektorienentwurfsraum 7.2 Einsatz der Steuerung und Regelung 7.3 Varianten der Kammanordnung 8 Zusammenfassung 8.1 Erreichte Ziele 8.2 Ausblick 8.3 Abschlussfazit Literaturverzeichnis Publikationen Anhang A Modellbildung und Simulation A.1 Elemente der strukturierten Analyse A.2 Grundlagen der Elektrostatik A.3 Ausführlicher Lagrange-Formalismus A.3.1 Q-Koordinaten A.3.2 PSI-Koordinaten A.4 Kapazitätskennlinien A.5 Impedanzrückkopplung A.6 Mikroscannerparameter A.7 Regelparameter der Simulation A.8 Stabilitätsnachweis der flachheitsbasierter Vorsteuerung mit Ausgangsstabilisierung Anhang B Experimentelle Verifikation B.1 Regelparameter der Messung B.2 Spannungs- und Winkelbeschleunigungsverläufe B.3 Ergebnisse der repetitiven Regelung mit Sägezahntrajektorie B.4 Impedanzmessung der Kammkapazitäten B.5 Geräteliste These

DEVELOPMENT OF SOLID TUNABLE OPTICS FOR ULTRA-MINIATURE IMAGING SYSTEMS

Ph.DDOCTOR OF PHILOSOPH