Fundamental investigations in the design of five-axis nanopositioning machines for measurement and fabrication purposes

The majority of nanopositioning and nanomeasuring machines (NPMMs) are based on three independent linear movements in a Cartesian coordinate system. This in combination with the specific nature of sensors and tools limits the addressable part geometries. An enhancement of an NPMM is introduced by the implementation of rotational movements while keeping the precision in the nanometer range. For this purpose, a parameter-based dynamic evaluation system with quantifiable technological parameters has been set up and employed to identify and assess general solution concepts and adequate substructures. Evaluations taken show high potential for three linear movements of the object in combination with two angular movements of the tool. The influence of the additional rotation systems on the existing structure of NPMMs has been investigated further on. Test series on the repeatability of an NPMM enhanced by a chosen combination of a rotary stage and a goniometer setup are realized. As a result of these test series, the necessity of in situ position determination of the tool became very clear. The tool position is measured in situ in relation to a hemispherical reference mirror by three Fabry-Pérot interferometers. FEA optimization has been used to enhance the overall system structure with regard to reproducibility and long-term stability. Results have been experimentally investigated by use of a retroreflector as a tool and the various laser interferometers of the NPMM. The knowledge gained has been formed into general rules for the verification and optimization of design solutions for multiaxial nanopositioning machines

Strain monitoring.

This chapter provides an overview of the use of strain sensors for structural health monitoring. Compared to acceleration-based sensors, strain sensors can measure the deformation of a structure at very low frequencies (up to DC) and enable the measurement of ultrasonic responses. Many existing SHM methods make use of strain measurement data. Furthermore, strain sensors can be easily integrated in (aircraft) structures. This chapter discusses the working principle of traditional strain gauges (Sect. 8.1) and different types of optical fiber sensors (Sect. 8.2). The installation requirements of strain sensors and the required hardware for reading out sensors are provided. We will also give an overview of the advantages and the limitations of commonly used strain sensors. Finally, we will present an overview of the applications of strain sensors for structural health monitoring in the aeronautics field

Metrologie in fünfachsigen Nanomess- und Nanopositioniermaschinen

Die vorliegende Arbeit stellt ein neuartiges Konzept für eine fünfachsige Nanomessmaschine zur Messung von Formabweichungen auf stark gekrümmten Asphären oder Freiform-Flächen vor. Bis zu einem Anstieg von bis zu 60° der Messobjektoberfläche kann der Sensor orthogonal zu dieser ausgerichtet werden. Unter vollständiger Einhaltung des Abbe-Komparatorprinzips wird das Messobjekt translatorisch in einem Bereich von 25mm 25mm 5mm relativ zu dem um zwei Rotationsachsen drehbaren Sensor bewegt. Die Messachsen der translatorischen Positionsmessung schneiden sich im so genannten Abbe-Punkt. Dieser Abbe-Punkt ist gleichzeitig auch der Antastpunkt des Sensors und der konstante Momentanpol der beiden Rotationsachsen zur Sensorrotation, die sich rechtwinklig in dem Abbe-Punkt schneiden. Zur Bestimmung der zufälligen und systematischen Positionsabweichungen des Sensors in Folge seiner Rotation wird ein Referenzmesssystem vorgestellt. Dieses besteht aus drei fest mit dem Sensor verbundenen, kartesisch angeordneten Fabry-Pérot-Interferometern, die kontinuierlich den Abstand des Sensors zu der Innenfläche einer Referenzhemisphäre messen. Die Messstrahlen der Fabry-Pérot-Interferometer schneiden sich dabei virtuell im Abbe-Punkt. Um die Formabweichung dieser Referenzhemisphäre zu bestimmen, wird ein in-situ-Kalibrierverfahren beschrieben, das die Bestimmung der Formabweichung mit den im System vorhanden Sensoren im Einbauzustand erlaubt. Dazu wird der Sensor durch einen Kugelreflektor im Abbe-Punkt (Kugellinse n=2) ersetzt. Dessen Positionsabweichung wird während der Rotation gemessen und zur Bestimmung der Formabweichung der Referenzhemisphäre genutzt. Basierend auf diesen Erkenntnissen wurde ein Prototyp des vorgestellten Konzepts aufgebaut und die Funktion des Referenzmesssystems verifiziert. Über einen großen translatorischen Verschiebungsbereich von 80 μm, kann die Verschiebung des Antastpunktes mit Hilfe des Referenzmesssystems auf +-200nm erfasst werden. Eine Wiederholungsmessung zwischen zwei Stellungen des Rotationssystems zeigte, dass die Antastpunktposition mit einer maximalen Abweichung von 27nm bestimmt werden kann. Die ausführliche theoretische Messunsicherheitsbetrachtung auf Grundlage von sechs Untermodellen ergibt eine Messunsicherheit für die Bestimmung des Antastpunktes von maximal 18nm p = 68%.This thesis presents a novel concept for a five-axes nano coordinate measuring machine which is designed to measure form deviations of strongly curved aspheres and freeform-surfaces. Up to a surface inclination of 60° of the sample, the sensor can be aligned perpendicularly to the local surface. In strict compliance with the Abbe-comparator principle, the sample is moved in a measuring volume of 25mm 25mm 5mm relative to the sensor which can be rotated in two axes. Those two axes of rotation cross perpendicular at the so-called Abbe-point which is also the intersection of the measurement axes of the linear movement. This Abbe point coincides with the measuring point of the sensor and is the constant instantaneous center of rotation of the sensor. To measure the position deviation of the sensor caused by the rotation, a reference-measuringsystem is shown. It consists of three cartesian arranged Fabry-Pérot-Interferometers connected to the sensor which are measuring the distance to the inner surface of the reference hemisphere. The measuring axes of those Fabry-Pérot-Interferometers virtually cross in the Abbe-point. To specify the form deviations of the reference-hemisphere an in-situ-calibration process is described. Therefore, the sensor is replaced by spherical reflector (ball lens n=2) whose position deviation is measured during the rotation and used to determine the form deviation of the reference hemisphere. Based on this concept, a prototype of the five-axes nano coordinate measuring machine was built and the functionality of the reference-measuring-system is verified. For a linear movement of 80 μm the sensors measurement point can be measured with a maximum deviation of +-200nm. Repeated measurements between two positions of the rotation-axes show that the measurement point can be determined with a maximum deviation of 27nm. The detailed theoretical measurement uncertainty budget based on six sub-models shows a maximum measurement uncertainty of the measurement point of 17nm p = 68%

A Regenerable Biosensing Platform for Bacterial Toxins

Waterborne diarrheal diseases such as travelers’ diarrhea and cholera remain a threat to public health in many countries. Rapid diagnosis of an infectious disease is critical in preventing the escalation of a disease outbreak into an epidemic. Many of the diagnostic tools for infectious diseases employed today are time-consuming and require specialized laboratory settings and trained personnel. There is hence a pressing need for fit-for-purpose point-of-care diagnostic tools with emphasis in sensitivity, specificity, portability, and low cost. We report work toward thermally reversible biosensors for detection of the carbohydrate-binding domain of the Escherichia coli heat-labile enterotoxin (LTB), a toxin produced by enterotoxigenic E. coli strains, which causes travelers’ diarrhea. The biosensing platform is a hybrid of two materials, combining the optical properties of porous silicon (pSi) interferometric transducers and a thermoresponsive multivalent glycopolymer, to enable recognition of LTB. Analytical performance of our biosensors allows us to detect, using a label-free format, sub-micromolar concentrations of LTB in solution as low as 0.135 μM. Furthermore, our platform shows a temperature-mediated “catch-and-release” behavior, an exciting feature with potential for selective protein capture, multiple readouts, and regeneration of the sensor over consecutive cycles of use

Design, Fabrication, and Characterization of a MEMS Based Thermally Actuated Fabry-Pérot Interferometer.

MEMS devices have become ubiquitous in consumer devices and are also being used to conduct experiments on the nano and micro scale. There is a growing need to test the properties of materials at the micro and nanoscale. In order to test those materials, a reliable method of sensing displacement is needed. Another growing area of MEMS research is in creating micro optical cavities that allow for manipulation and control of atoms in QED research. This thesis describes a MEMS based thermally actuated Fabry-Pérot cavity interferometer that has potential as a displacement sensing mechanism for use in material testers and other devices which require motion feedback. Additionally the device has a potential application as a tunable cavity for use in cavity QED experiments. The theory behind the operation of the thermal actuator and the Fabry-Pérot cavity are shown. The design of the actuator and cavity is also discussed in detail as well as the fabrication of both structures. Experiments of the device were performed in a vacuum and in air. The data obtained from experiments are compared to FEA and MATLAB simulations to verify the performance of the device