Beitrag zur Gestaltung und Herstellung einer integrierten Mikropositionierungssystem

Modern positioning systems are significantly applied in many engineering fields dealing with products emerging from different technologies at macro-, micro- and nanoscale. These systems are the back-bone systems behind any manipulation task in these areas. Currently, miniaturization trend have led numerous scientific communities to realize down scaled versions of these systems with a footprint size up to few hundreds of millimeters. These miniature positioning systems are cost effective solutions in many micro applications. This thesis presents the development of a miniature positioning system integrated with a non-contact long range displacement sensor. The uniqueness of the presented positioning system lies in its simple design with ability to perform micrometer to millimeter level strokes with pre-embedded auto guidance feature. Its design consists of a mobile part driven with four electromagnetic linear motors. Each motor consists of a fixed two phase current carrying planar electric drive coil and permanent magnet array that is realized with 14 permanent magnets arranged in north-south configuration. In order to achieve smooth motion a four point contact technique with hemispherical glass beads has been adapted to minimize the adherence effect. The overall design of the planar positioning system have been optimized to achieve a footprint size of 80 mm × 80 mm. The device can deliver motion within working range of 10 mm × 10 mm in xy-plane with sub micrometer level resolution at a speed of 12 mm/s. The device is capable to deliver a rotation motion of ±11° about the z axis in the xy-plane. Secondly, in order to measure the displacement performed by the mobile part, a non-contact long range linear displacement sensor has been designed. The overall dimensions of the sensor were optimized using a geometrical model. The fabrication of the sensor has been carried out via microfabrication in silicon material to achieve compact dimensions, so that it could be integrated in the mobile part of the positioning system. The sensor is able to provide 30.8 nm resolution with a linear measurement range of 12.5 mm. At the end, a novel cross structure has been designed and fabricated using microfabrication with the perspective to integrate the long range sensor.Moderne Positioniersysteme werden in vielen aufstrebenden Bereichen der Technik eingesetzt. Die Produkte stammen hierbei aus unterschiedlichen Technologiebereichen, die den Makro-, Mikro- und Nano- Maßstab abdecken. Diese Systeme bilden die Basis jeder Manipulationsaufgabe, in diesen Bereichen. In jüngster Zeit hat der Miniaturisierungstrend dazu geführt, dass in zahlreichen wissenschaftlichen Bereichen immer kleinere Versionen von Systemen realisiert wurden. Die typischen Abmessungen wurden dabei auf einige hundert Millimeter reduziert. Diese Miniatur Positioniersysteme sind kostengünstige Lösungen in vielen Mikro Anwendungen. Die vorliegende Arbeit stellt die Entwicklung eines Miniatur-Positioniersystems dar, in welches ein berührungsloser Wegsensor für lange Distanzen integriert wurde. Die Einzigartigkeit dieses Positionierungssystems liegt in der Einfachheit der Konstruktion in Kombination mit der Fähigkeit Bewegungen vom Mikrometer bis zum Millimeter Bereich mittels einer eingebetteten Autopilotfunktion auszuführen. Das Design besteht aus einem beweglichen Teil, welches mit vier elektrischen Linearmotoren angetrieben wird. Jeder Motor besteht aus zwei Teilen: Einem planaren elektrisch angetriebenen Schlitten und einer Anordnung von Permanentmagneten. Die Anordnung ist mit 14 Permanentenmagneten in Nord-Süd Ausrichtung realisiert. Um eine sanfte Bewegung zu erreichen wird eine Vierpunktauflage mit halbkugelförmigen Glasperlen verwendet. Hierdurch werden Adhäsionseffekte minimiert. Das Positionierungssystem kann Bewegungen im Arbeitsbereich von 10 mm × 10 mm in der xy-Ebene mit Submikrometer Auflösung und einer Geschwindigkeit von 12 mm/s ausführen. Das Gerät ist in der Lage eine Drehbewegung von ±11° um die z-Achse in der xy-Ebene auszuführen. Weiterhin wurde, um die Verschiebung des beweglichen Teils zu messen, ein kontak tloser Langstrecken-Wegsensor entworfen. Die Gesamtabmessungen des Sensors wurden mit einem geometrischen Modell optimiert. Die Herstellung des Sensors wurde mittels Mikrostrukturierung in Silizium ausgeführt um eine kompakte Abmessung zu erreichen, so dass es in den beweglichen Teil des Positionierungssystems integriert werden konnte. Der Sensor erreicht eine Auflösung von 30,8 nm in einem linearen Messbereich von 12.5 mm. Am Ende der Arbeit wurde eine neue Kreuz-Struktur konzipiert und hergestellt, gleichfalls mit Hilfe der Mikrostrukturierungstechnik. Hieraus ergibt sich die Perspektive den Langstrecken Wegsensor problemlos zu integrieren

Enabling hybrid process metrology in roll-to-roll nanomanufacturing: design of a tip-based tool for topographic sampling on flexible substrates

This work seeks to demonstrate the efficacy of a novel approach for topography measurement of nano-scale structures fabricated on a flexible substrate in a roll-to-roll (R2R) fashion. R2R manufactured products can be extremely cost competitive compared to more traditional, silicon wafer or glass panel based nanofabrication solutions, in addition to the unique and often desirable mechanical properties inherent to flexible substrates. As such, flexible nanomanufacturing is an area of immense research interest. However, despite the significant potential of these products for a variety of applications, developing manufacturing systems from lab-scale prototypes to pilot- or high volume manufacturing (HVM) has often proven both difficult and infeasibly expensive as research investment and achievable process yield limit advancement. One of the most significant capability gaps in current art, and roadblocks on the path towards adoption of R2R nanomanufacturing, is the lack of high-throughput, nanometer-scale metrology for process development, real-time control, and yield enhancement. This dissertation presents the design of a tip-based measurement tool implementing atomic force microscope (AFM) probes manufactured with a micro-electro-mechanical system (MEMS) approach to the challenge of sub-micron topography measurement which is also compatible with R2R manufacturing on flexible substrates. A proof-of-concept prototype tool with subsystems to regulate a flexible web, isolate and position the atomic force microscope probe, and measure features on the substrate, all coordinated by a real-time embedded control system, was designed and fabricated. The positioning subsystem was evaluated dynamically to ensure initial design requirements were met, and stationery, step-and-scan results were presented. However, to wholly meet this extent need for in-line R2R metrology, a system capable of atomic force microscope scanning despite a continuous, non-zero substrate velocity is required - any regular stoppage of the web in a R2R process all but dooms economically viable production throughput. Refinement and redesign of the proof-of-concept tool was driven by new system requirements to meet this goal, in addition to lessons learned from the initial prototype. Improvements focused on upgrading the web handling spindle design and mechatronics, tool power electronics, moving structures, and control algorithms used for high-speed synchronous positioning of the atomic force microscope and web. The culmination of this work will serve to introduce a new measurement framework which may be used to accelerate and enable future research in R2R manufacturing of nanofeatured products.Mechanical Engineerin

Two-dimensional remote interferometric stage encoder through a single access port using range-resolved interferometry

In this work, using our range-resolved interferometry (RRI) signal processing technique, we present a novel approach to multidimensional displacement measurements using only a single optical access port and very simple optical setup. By utilising surface reflections from a stage-mounted moving beamsplitter and two orthogonal stationary reference mirrors, two interferometers for the two Cartesian measurement directions are formed. With RRI, the interferometric phase signals of both interferometers can be independently demodulated, allowing simultaneous measurements of displacement in both dimensions using a single continuous-wave laser diode source and a single photodetector. In this paper, the capabilities of this approach are demonstrated using a proof-of-concept experiment with a multidimensional Piezoelectric stage performing a variety of stage movements. Measurements of displacements over a nominal stage working range of ±50μm are presented, demonstrating independent, simultaneous displacement measurements of two dimensions. The presented measurements show nanometer-level displacement resolutions with typical noise densities of 0.02 nm/√Hz over a 21 kHz bandwidth. It is thought that this approach could offer an interesting alternative to existing interferometric techniques for multi-dimensional metrology, benefiting from both simplicity and cost-effectiveness whilst maintaining the advantages that make optical techniques attractive to scientific and industrial applications

Interferometrische Encoder zu lineare Verschiebungsmetrologie

Currently one of the most challenging demands on linear displacement metrology comes from positioning of the wafer stages of the lithography machine tools, which requires measurement ranges of hundreds of millimeters and measurement uncertainties of several nanometers and even below. At present, only displacement interferometers and interferometric encoders can be managed to meet these requirements; but to do so, interferometers need very strict environmental controlling if not vacuum. Therefore more and more attentions are paid to interferometric encoders due to their lower sensitivities to the refraction-index fluctuations of ambient air and the wavelength deviations. In this work, a three-channel homodyne interferometric (TCHOI) encoder, a two-dimensional homodyne interferometric (2DHI) encoder and a differential heterodyne interferometric (DIHEI) encoder were developed: The TCHOI encoder had three channels which used different diffraction orders but measured the same position on the scale grating. The design of this TCHOI encoder provided an opportunity to study the suspected different measurement uncertainties caused by the correlations between the imperfections of the grating scale and different diffraction orders. The periodic nonlinearities of the TCHOI encoder were ± 50 pm in channel 1, ± 150 pm in channel 2 and ± 70 pm in channel 3, when HEIDENHAIN EIB 741 was employed. As a home-developed phase meter and off-line correction were used, its channel 1 had a periodic nonlinearity of ± 10 pm. The 2DHI encoder was designed to measure the displacements in X- and Z- directions with one dimensional grating scale. Its principle was proven by the proof-of-principle experiment. The DIHEI encoder was based on differential measurement principle and a polarization-mixing-avoiding strategy. It had a periodic nonlinearity of less than ± 30 pm (without correction) and system stabilities of 38 pm (?) and 100 pm (?) over 30 seconds and one hour respectively.Eine der anspruchsvollsten Anforderungen der linearen Verschiebungsmessungen liegt derzeit in der Positionierung von Wafertischen für Lithografiemaschinen, die Messbereiche von mehreren hundert Millimetern und Messunsicherheiten im Bereich von einigen Nanometern bis hin zu Sub-Nanometern erfordern. Momentan können nur Interferometer und interferometrische Encoder diese Anforderungen erfüllen. Im Vergleich zu Encodern benötigen Interferometer jedoch sehr genau definierte Umgebungsbedingungen, um diese Anforderungen zu erfüllen. Deswegen werden interferometrische Encoder immer populärer. In dieser Arbeit wurde ein dreikanaliger homodyner (3KH) Encoder, ein zweidimensionaler homodyner (2DH) Encoder sowie ein differentieller heterodyner (DH) Encoder entwickelt. Der 3KH Encoder hatte drei Kanäle, die verschiedene Beugungsordnungen verwenden, wobei die gleiche Position auf einem Gittermaßstab gemessen wurde. Das Design des 3KH Encoder war dahingehend konzipiert wurden, um mögliche unterschiedliche Messunsicherheiten, hervorgerufen durch die Korrelationen zwischen Unvollkommenheiten des Maßstabs und der verschiedenen Beugungsordnungen, zu untersuchen. Wenn zur Signalauswertung ein HEIDENHAIN EIB741 verwendet wurde, hatte der 3KH Encoder periodische Nichtlinearitäten (PN) von ±50 pm im Kanal 1, ±150 pm im Kanal 2 und ±70 pm im Kanal 3. Desweiteren wurde eine selbstentwickelte Auswerteelektronik und eine Heydemannkorrektur genutzt, wodurch ein PN von ±10 pm erzielt wurde. Der 2DH Encoder wurde prinzipiell ausgelegt, um Verschiebungen sowohl entlang des eindimensionalen Gittermaßstabes als auch der orthogonalen Richtung zu bestimmen. Das Prinzip wurde durch Experiment nachgewiesen. Der DH Encoder basierte auf einem differenziellen Messprinzip und war gezielt zur Vermeidung von Polarisationsmischung entwickelt worden. Es konnte ohne Korrektur ein PN von ±30 pm bestimmt werden. Zudem wurden eine Stabilität von 38 pm (?) über 30 Sekunden und 100 pm (?) über eine Stunde gemessen

MEMS Actuation and Self-Assembly Applied to RF and Optical Devices

The focus of this work involves optical and RF (radio frequency) applications of novel microactuation and self-assembly techniques in MEMS (Microelectromechanical systems). The scaling of physical forces into the micro domain is favorably used to design several types of actuators that can provide large forces and large static displacements at low operation voltages. A self-assembly method based on thermally induced localized plastic deformation of microstructures has been developed to obtain truly three-dimensional structures from a planar fabrication process. RF applications include variable discrete components such as capacitors and inductors as well as tunable coupling circuits. Optical applications include scanning micromirrors with large scan angles (>90 degrees), low operation voltages (<10 Volts), and multiple degrees of freedom. One and two-dimensional periodic structures with variable periods and orientations (with respect to an incident wave) are investigated as well, and analyzed using optical phased array concepts. Throughout the research, permanent tuning via plastic deformation and power-off latching techniques are used in order to demonstrate that the optical and RF devices can exhibit zero quiescent power consumption once their geometry is set

Development of Sensing Systems for Improving Surgical Grasper Performance

Minimally invasive techniques play a vital and increasing role in modern surgery. In these procedures, surgical graspers are essential in replacing the surgeon’s fingertips as the main manipulator of delicate soft tissues. Current graspers lack haptic feedback, restricting the surgeon to visual feedback. Studies show that this can frequently lead to morbidity or task errors due to inappropriate application of force. Existing research has sought to address these concerns and improve the safety and performance of grasping through the provision of haptic feedback to the surgeon. However, an effective method of grasping task optimisation has not been found. This thesis explores new sensing approaches intended to reduce errors when manipulating soft tissues, and presents a novel tactile sensor designed for deployment in the grasper jaw. The requirements were first established through discussion with clinical partners and a literature review. This resulted in a conceptual approach to use multi-axis tactile sensing within the grasper jaw as a potential novel solution. As a foundation to the research, a study was conducted using instrumented graspers to investigate the characteristics of grasp force employed by surgeons of varying skill levels. The prevention of tissue slip was identified as a key method in the prevention of grasper misuse, preventing both abrasion through slip and crush damage. To detect this phenomena, a novel method was proposed based on an inductive pressure sensing system. To investigate the efficacy of this technique, experimental and computational modelling investigations were conducted. Computational models were used to better understand the transducer mechanisms, to optimise sensor geometry and to evaluate performance in slip detection. Prototype sensors were then fabricated and experimentally evaluated for their ultimate use in slip detection within a surgical grasper. The work concludes by considering future challenges to clinical translation and additional opportunities for this research in different domains

Integrated polymer photonics : fabrication, design, characterization and applications

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Three-dimensional interferometric stage encoder using a single access port

We present a novel multi-dimensional positional encoder approach that uses range-resolved interferometry (RRI) to simultaneously interrogate multiple interferometers differing in optical path length, using only a single photo detector and a single diode laser. Employing only stage-mounted non-polarising beamsplitters and reflections from three orthogonal, externally mounted, planar mirrors, three Cartesian measurement directions are formed, that when combined with measurements from a stage-mounted reference reflection, allow for three-dimensional measurements of stage motion obtained via a single access port. Through a variety of movements of a three-dimensional Piezo-electric stage over its nominal stage working range of ± 50 μm, simultaneous measurements of displacements from three orthogonal dimensions are acquired with a 10 kHz quadrature bandwidth, achieving typical displacement noise densities of below 0.4 nm/√Hz with the noise floor dropping to below 0.1 nm/√Hz above 50 Hz, as well as high linearity with cyclic errors amplitudes well below 1 nm in all three directions

Novel applications and stabilisation for widely wavelength modulated laser interferometry for precision dimensional metrology.

The need for precision dimensional metrological techniques is always increasing, including high precision displacement measuring metrology used to precisely and accurately position stages, components and machines. Laser interferometry is widely considered the most precise technique available for single dimensional displacement measurements, however extending this to multiple dimensions typically involves complex and costly interrogation systems. In this thesis, a series of novel multi-dimensional stage encoder designs and experimental results are presented as an application of a state-of-the- art metrological technique, that uses sinusoidal wavelength modulation and range-dependant signal processing to multiplex the signals from multiple interferometers into a single interferometric signal. Using range-resolved interferometry (RRI), a series of interferometers comprising measurements in multiple dimensions are multiplexed onto a single photodetector, which are then are independently and concurrently demodulated and evaluated. This technique is applied to novel designs for a 2-dimensional displacement encoder, a 3-dimensional displacement encoder and a dual-beam angle encoder, where unlike prior work which has typically required complex optical setups involving polarisation-sensitive optical components and detectors, uses only minimal, simple bulk optic components to evaluate multiple dimensions simultaneously. In this work, nonlinearities below 1 nm along with typical displacement noise levels below 0.4 nm/√Hz are presented for experimental results of ±50 µm controlled stage motions, showing results which are highly comparable to existing techniques. Further to this, in order to make high precision results with confidence, high-stability lasers are required. In non-modulated and weakly modulated wavelength regimes, there are a significant number of techniques available for laser stabilisation, for both short-term and long-term requirements and linked to highly stable references. However, for widely-wavelength modulated techniques such as RRI, where the modulation depth is several orders of magnitude greater than standard reference widths, the vast majority of existing techniques are either unsuitable or significantly less-effective. In this thesis, a novel technique for long-term stabilisation of a widely wavelength modulated laser to a high stability reference standard is presented. Introduced as "swept absorption line locking", the principle behind this technique, in addition to experiments to test the efficacy of this technique are presented. Included in this, is comparison to a highly-stabilised helium-neon laser, which is often considered a "gold-standard" for stability, where co-linear displacement measurements of a Michelson interferometer are performed and compared to determine the RRI evaluation wavelength. The results presented here show fractional stabilities as low as 6×10−⁸ over timescales of ∼1000 seconds using this novel stabilisation technique, and the comparison to the HeNe laser interferometer shows good agreement between the calculated RRI evaluation wavelength and the expected stabilised value within calculated uncertainties.PhD in Transport System