Nanonewton force generation and detection based on a sensitive torsion pendulum

In this paper, we introduce the experiment based on a sensitive torsion pendulum for measuring and calibrating small forces at nanonewton scale. The force standard for calibration is the universal gravitation between four masses separated by known distances. It is realized by two test masses suspended as the part of torsion pendulum and two source masses on a rotation table. Two force generation mechanisms, optical force from radiation pressure and electrostatic force by capacitive actuation unit, are designed and will be calibrated by the gravitation force. We present our recent results of radiation pressure measurements, and describe the design of capacitive displacement sensing/actuating unit.Comment: This work has been presented on Conference on Precision Electromagnetic Measurements, 8-13 June 2008, Broomfield, Colorad

High resolution force measurement system for Lorentz force velocimetry

Die Lorentzkraft-Anemometrie wurde als neuartige Methode für die berührungslosen Geschwindigkeitsmessungen leitfähiger Strömungen entwickelt. Die induzierte Lorentzkraft ist proportional zur Strömungsgeschwindigkeit. Mit einem Kraftmesssystem kann die Reaktionskraft der induzierten Lorentzkraft, die auf das integrierte Magnetsystem wirkt, gemessen werden. Dadurch kann die Strömungsgeschwindigkeit bestimmt werden. Die Eigenschaften der Geschwindigkeitsmessung hängen von den Eigenschaften des Kraftmesssystems ab. Bei Fluiden mit geringer elektrischer Leitfähigkeit, wie z.B. Elektrolyten, liegt die erzeugte Lorentzkraft im Bereich von Mikronewton und darunter. Das Kraftmesssystem unterstützt eine Masse eines Magnetsystems von ca. 1 kg. Deshalb ist das Ziel dieser Arbeit ein Kraftmesssystem zu entwickeln, welches auf der einen Seite eine verbesserte Kraftauflösung in horizontaler Richtung für niedrigleitende Elektrolyte aufweist und auf der anderen Seite die Tragfähigkeit der Eigenlast von über 1 kg zur Unterstützung des integrierten Magnetsystems gewährleistet. In vorherigen Arbeiten wurde die Wägezelle nach dem Prinzip der elektromagnetischen Kraftkompensation (EMK-Wägzelle) in aufgehängter Konfiguration mit dem 1 kg Magnetsystem zur Messung der Lorentzkraft verwendet. Basierend auf verschiedenen Experimenten in dieser vorgestellten Arbeit wird festgestellt, dass aufgrund des mechanischen Aufbaus sowohl Neigungsempfindlichkeit als auch Steifigkeit der EMK-Wägezelle stark von der genutzten Konfiguration und dem Gewicht der unterstützten Eigenlast abhängig sind. Um die durch diese Abhängigkeiten verursachten Einflüsse zu minimieren, wird ein Torsionskraftmesssystem basierend auf dem Prinzip der Torsionswaage entwickelt. Diese ist theoretisch neigungsunempfindlich und behält bei unterschiedlichen Eigenlasten eine konstante Steifigkeit bei. Die Auslenkungsmessungen werden verwendet, um die Ausgangsspannung des Torsionskraftmesssystems sowohl in Positionswerten als auch in Kraftwerten zu kalibrieren. Ein Closed-Loop-Betriebsmodus wird mithilfe eines PID-Reglers aufgebaut, mit dem die Grenzfrequenz von 0,002 Hz auf 0,1 Hz verbessert wird. Ein spezialangefertigter kapazitiver Aktor wird entwickelt, um eine rückführbare elektrostatische Kraft zu erzeugen, die anstelle der elektromagnetischen Kraft verwendet werden kann. Um die elektrostatische Kraft zu kalibrieren, werden drei Methoden genutzt: (a) durch Messung des Kapazitätsgradienten; (b) durch Vergleich mit einer elektromagnetischen Kraft und (c) durch Messung des induzierten Stroms in einem Velocity-Modus. Bei der Datenauswertung wird eine numerische Verarbeitung mit Newton-Polynominterpolation durchgeführt, um die thermischen und seismischen Störungen und Driften während der Messungen zu schätzen und zu korrigieren. Im Vergleich zu vorherigen Arbeiten, wo die Kraftauflösung auf 20 nN und die Eigenlast auf 3 kg begrenzt waren, ist das Torsionskraftmesssystem in der Lage, Kräfte bis zu 2 nN aufzulösen und eine Eigenlast bis zu 10 kg zu tragen. Schließlich wird die sogenannte Halb-Trocken-Kalibrierung am Torsionskraftmesssystem durchgeführt. Die Messempfindlichkeit wird für unterschiedliche Leitfähigkeiten ermittelt. Basierend auf den experimentellen Ergebnissen, zeigt das Torsionskraftmesssystem das Potential, um Messungen mit weiter geringerer Leitfähigkeit bis hinunter zu 0.0064 S/m durchzuführen.The Lorentz force velocimetry (LFV) was introduced as a novel method for non-contact velocity measurements of electrically conducting flows. The induced Lorentz force is proportional to the flow velocity. Using the force measurement system (FMS), the reaction force of the induced Lorentz force that acts on the integrated magnet system can be measured, the velocity of the moving flow can be thereby determined. The characteristics of the measured flow velocity depend on the properties of the FMS. For weakly electrically conducting fluids like electrolytes, the induced Lorentz force is in the range of micronewton and below. The mass of the magnet system supported by the FMS is approximately 1 kg. Therefore, the aim of this work is to develop a FMS with the improved force resolution in horizontal direction for weakly conducting electrolytes, and also with the dead load capacity of over 1 kg for supporting the integrated magnet system. In previously developed FMSs, the electromagnetic force compensation (EMFC) weighing cell was used in its suspended configuration carrying the 1 kg magnet system to measure the Lorentz force. Based on various experiments in the presented work, it is found that due to its mechanical structure, the tilt sensitivity and the stiffness of the EMFC system are strongly dependent from the configuration it is used and the weight of dead load it supports. In order to minimize the influences caused by the dependency, the torsion force measurement system (TFMS), which is theoretically tilt-insensitive as well as retains a constant stiffness with different applied dead load values, is developed in this work based on the principle of torsion balance. The deflection measurement as a traceable method is introduced to calibrate the output of the TFMS into positioning as well as force values. The closed-loop operation mode is built based on PID-controller, by which the cutoff frequency is improved from lower than 0.002 Hz to 0.1 Hz. A customized capacitive actuator is set up to create traceable electrostatic force (ESF), which is a reasonable replacement of the electromagnetic force (EMF). Then, the ESF is calibrated using three methods: (a) by measuring capacitance gradient; (b) by comparing with the EMF and (c) by measuring the induced current in a velocity mode. Numerical processing using newton's polynomial interpolation is carried out in the data evaluation to estimate and compensate the thermal and seismic drifts during the measurements. In comparison with previous work where the force measurement resolution was limited to 20 nN and dead load up to 3 kg, the TFMS is able to resolve forces down to 2 nN and also makes it possible to carry the dead load up to 10 kg. Finally, the so-called semi-dry calibration is carried out on the TFMS. The measuring sensitivity is obtained in respect to different conductivity values. Based on the experimental results, the TFMS shows a potential to implement velocity measurements with further lower conductivity down to 0.0064 S/m

Development and characterisation of traceable force measurement for nanotechnology

Traceable low force metrology should be an essential tool for nanotechnology. Traceable measurement of micro- and nanonewton forces would allow independent measurement and comparison on material properties, MEMS behaviour and nanodimensional measurement uncertainties. Yet the current traceability infrastructure in the UK is incomplete. This thesis describes the incremental development of the low force facility at the National Physical Laboratory (NPL). The novel contribution of this thesis has three components. First, specific modifications to the NPL Low Force Balance were undertaken. This involved developing novel or highly modified solutions to address key issues, as well as undertaking detailed comparions with external ans internal traceability references. Second, a triskelion force sensor flexure was proposed and mathematically modelled using both analytical and finite element techniques, and compared to experimentally measured spring constant estimates. The models compared satisfactorily, though fabrication defects in developed prototype artefacts limited the experimental confirmation of the models. Third, a piezoelectric sensor approach for quasistatic force measurement was proposed, experimentally evaluated and rejected. Finally, an improved design for a low force transfer artefact system is presented, harnessing the findings of the reported investigations. The proposed design combines proven strain-sensing technology with the advantageous triskelion flexure, incorporating an external stage and packaging aspects to achieve the requirements for a traceable low force transfer artefact

Yukawa force spectroscopy to search for violations of Newton’s law of gravity below 1 μm distances

Gravity is well tested on several length scales, but some unified theories predict deviations in the region below 1 mm. In this thesis I will present a method to search for such deviations in the sub-micrometre length scale. Below 1 μm, the electrostatic and the Casimir force are stronger than the gravitational force by some magnitudes. To distinguish these forces, I have designed a new force measurement setup based on the frequency modulation AFM technique. Utilizing a quartz based parallelogram cantilever, it is feasible to measure these forces with sufficient accuracy for us to set new constraints for possible deviations of gravity. In this thesis I will present a new method of measuring such deviations of gravity, and show the initial results I have obtained using it. This will show that the measurement concept works, but that improvements are necessary before we can achieve optimum measurement uncertainty

Modelling, implementation and validation of polymeric planar spring mechanisms

This thesis explores, by means of modelling and physical experiments, variant designs for triskelion devices, a type of planar exure mechanism widely considered for use in micro-probe suspensions and, more recently, force transfer artefacts. The accurate measurement of low force is challenging problem that has wide range of force related applications. A lot of attention has been paid worldwide during last decade within and beyond the National Metrology Institutes (NMIs) to measuring low forces. A major concern is how to provide traceability for micro- to nanonewton level forces that is highly reliable and could be used for real machine calibration. The current consensus is that this process requires special secondary standards and novel artefacts to transfer such standards to working systems. The latter provides the motivation for this thesis, which makes the following main contributions. A published linear elastic model has been considerably enhanced and generalised to enable the study of a wide range of variants from the one widely-used design of triskelion device. Triskelion and tetraskelion software programs implement this new model, providing a new tool for computing forces, moments, stress, strain, axial stiffness and torsional stiffness for devices before their fabrication. It has been used to explore widely the sensitivity of the devices to changes in design parameters such as suspension leg geometry and 'elbow' angles. To provide essential physical verification of the practicality of a linear model, a low-cost technique has been developed for making small triskelion test samples. This was used with a new test-rig configuration to measure polymeric triskelion devices under loads in the 1 mN to 1N region with deflections up to around 1 mm. Experiments have determined the onset and characteristics of non-linear spring behaviour in typical devices and have verified the general predictions from the new model. The overall conclusion to be drawn is that at large de ection the spring characteristics follow a cubic law (stiffening). However, during the initial stages of the de ection the linear term dominates over a range that is quite sufficiently wide for practical use as force test artefacts. The polymeric test devices performed well, behaving reasonably closely to predicted values in the linear (model) region. The promising results indicate its prospects for use in low force technology in the future

Trapping in a material world

The ability to manipulate small particles of matter using the forces of light, optical trapping, forms the basis of a number of exciting research areas, spanning fundamental physics, applied chemistry and medicine and biology. Historically, a largely unexplored area has been the influence of the material properties of the particle on the optical forces. By taking a holistic approach in which the properties of the particle are considered alongside those of the light field, the force field on a particle can be optimized, allowing significant increases of the optical forces exerted and even the introduction of new forces, torques, and other physical effects. Here we present an introduction to this newly emerging area, with a focus on high refractive index and antireflection coated particles, nanomaterial particles, including metallic nanoparticles, optically anisotropic particles, and metamaterials. Throughout, we discuss future perspectives that will extend the capabilities and applications of optical trapping and shape future avenues of research in this burgeoning field.Publisher PDFPeer reviewe

Synthesis and performance analysis of ammonium dinitramide

Ammonium dinitramide as non-corrosive, high performance, and Eco-friendly propellant was first synthesized by Russians in early 1970s, and then independently in early 1990s by Stanford Research International. Since then, there has been increased interest in its synthesis and performance analysis. Therefore, this project was aimed to enhance the study of ADN and explore new areas of its application. This project has 3 objectives where syntheses, prilling, electrolysis of ADN were studied. In first objective, a new, modified ADN synthesis method was developed. This method was able to synthesize ADN at near-zero temperature by nitration of potassium sulfamate with mixture of nitric acid, sulfuric acid and trifluoroacetic acid. Once synthesized, parametric studies were performed to increase the reaction yield. It was developed by analyzing the existing ADN synthesis methods and their reaction mechanisms. In the second objective, ADN prilling and sonication was performed via ultrasound treatment and the results were compared with ADN obtained by existing methods. It was necessary to perform prilling i.e. conversion of ADN crystal morphology because, ADN in its raw form have long needle like structure. Secondly, it has low critical humidity level of ADN i.e. 55.2%RH renders practical and handling issue in humid climate. Therefore, an ultrasound based prilling and coating method was developed, where ADN was sonicated in toluene as sonication medium along with surfactants and coating polymers. With this method, it was possible to combine prilling and coating of ADN particles into single step with results comparable to conventional melt prilling method. In third objective, ADN based liquid monopropellant named FLP-103 was electrolytically decomposed and its performance was analyzed in micro thrusters. In order to decompose ADN by electrolysis, Micro thrusters were fabricated with Polydimethyl siloxane (PDMS) and the experiments were analyzed by video footage, load cell thrust measurement and self-fabricated thrust measurement system. The thrusters were fabricated using combination of embossing and engraving techniques with PDMS to eliminate leakages and backpressure. Thrust measurement system, based on PDMS made torsion rod was developed as a proof of concept by using low cost sensors LDC-1000 from Texas instruments. Its results were compared with the results obtained by load cell thrust measurement. The results showed that ADN can be successfully decomposed via electrolysis in micro thrusters and electrolysis occurs predominately at cathode

Prototypenentwicklung eines oberflächen-integrierten Mikrosensor Systems für 3D Traktionskraftmessungen durch DHM/DIC

In times of a rapid development and growing market in robotics, high-tech protheses and the personalization of medicine, biomimicking natural materials like artificial tissue are of central interest within research and industry. To fully understand the structure-function relations within living systems, comprehensive knowledge about the smallest living block, the cell, and its biomechanics are a central topic in world-wide research. However, there is so far no comprehensive technique established that can measure 3D cell forces simultaneously and quantitatively. In this project, a novel surface-integrated mechano-optical microsensor system has therefore been conceptualized, prototyped and tested, which allows for the record of pico- to micronewton traction forces in three dimensions simultaneously. First, adequate microsensor elements were designed via topology optimization and linear static finite element analysis. These designs were fabricated by micromachining processes of biocompatible thin films of nickel-titanium and amorphous silicon. Furthermore, a plasma etching process was developed to fabricate polydimethylsiloxane sensor elements. For accurate and quantitative traction force measurements, AFM cantilever based calibrations of the out-of-plane and in-plane sensor element spring constants were established. For the first time, a diamagnetic levitation force calibrator was used as an adequate pre-calibration method for the sensor elements with a high accuracy of 1 %. For the cost-efficient, simple, compact, variable and sensitive mechano-optical readout, a setting was conceptualized and tested based on the combination of digital holography and digital image correlation. To control cell adhesion, a high-throughput micro-nano structuring method was developed based on the fusion of ink-jet printing with the established method of diblock-copolymer micelle nanolithography.In Zeiten schneller Entwicklung und wachsender Märkte in der Robotik, der high-tech Prothetik und der personalisierten Medizin ist die Biomimetik natürlicher Materialien wie beispielsweise künstliche Haut von zentralem Interesse in Forschung und Industrie. Um die Struktur-Funktions-Beziehungen in lebenden Systemen umfassend zu verstehen ist die umfangreiche Wissenserweiterung hinsichtlich des kleinsten lebenden Bausteins, der Zelle, und seiner Biomechanik Gegenstand weltweiter Forschungsprojekte. Dennoch gab es bis jetzt keine Methode, die 3D Zellkräfte simultan und quantitativ messen kann. In diesem Projekt wurde ein neuartiges, oberflächen-integriertes, mechano-optisches Mikrosensorsystem konzeptioniert, prototypisiert und getestet, das die Messung piko-bis mikronewton kleiner Zugkräfte gleichzeitig in alle drei Dimensionen ermöglicht. Die Sensorelemente wurden mittels Topologieoptimierung und linear statischer Finite Elementanalyse konzipiert. Diese Designs wurden in Mikromaterialbearbeitungsprozessen aus biokompatiblen Nickel-Titan und amorphen Silizium-Dünnschschichten hergestellt. Desweiteren wurde ein Prozess entwickelt, um Polydimethylsiloxan basierte Sensorelemente herzustellen. Für genaue, quantitative Zugkraftmessungen wurden AFM-Cantilever basierte Kalibrierungen der axialen und lateralen Sensorelement-Federkonsten etabliert. Zum ersten Mal wurde dabei ein diamagnetischer Levitationskraftkalibrator mit einer Genauigkeit von 1% als geeignete Kalibrierungsmethode für die Sensorelemente genutzt. Für eine günstige, einfache, kompakte, variable und im Nanometerbereich empfindliche mechano-optische Datenauslesung wurde ein Aufbau konzeptioniert und getestet, in dem digitale Holographie und digitale Bildkorrelation kombiniert werden. Zur Zell-Adhäsionskontrolle wurde eine Hochdurchsatz-Mikro-Nanostrukturierungsmethode entwickelt, die auf der Kombination von Ink-Jet Drucken mit der etablierten Methode der Diblock-Copolymer Mizellen Nanolithographie basiert

Study of Thin-Film Surfaces

Disertační práce se zabývá studiem povrchových vlastností jedno a vícevrstvých filmů deponovaných z vinyltriethoxysilanových a tetravinylsilanových monomerů. Zabývá se také charakterizací adheze jednovrstvých filmů z tetravinylsilanu. Plazmaticky polymerizované tenké vrstvy byly připraveny na leštěných křemíkových substrátech pomocí plazmové depozice z plynné fáze za ustálených podmínek. Povrchové vlastnosti vrstev byly charakterizovány pomocí různých metod rastrovací sondové mikroskopie a nanoindentačních technik jako je konvenční a cyklická nanoindentace. Vrypový test byl použit pro charakterizaci vlastností adheze vrstev. Jednovrstvé filmy připravené za různých depozičních podmínek byly charakterizovány s ohledem na povrchové morfologie a mechanické vlastností (modul pružnosti, tvrdost). Výsledky morfologie povrchu, analýzy zrn, nanoindentace, analýzy konečných prvků a modulů mapování pomohly rozlišit hybridní charakter filmů, které byly deponovány při vyšších výkonech RF-výboje. Nový přístup byl použit v povrchové charakterizaci vícevrstvého filmu pomocí rastrovací sondové mikroskopie a nanoindentace. Adhezívní chování plazmaticky polymerizovaných vrstev různých mechanických vlastností a tloušťek bylo analyzováno pomocí normálních a laterálních síl, koeficientu tření, a snímků vrypů získaných pomocí mikroskopie atomárních sil.doctoral thesis deals with the study of surface properties of single-layer and multilayer thin films deposited from of vinyltriethoxysilane and tetravinylsilane monomers. It also deals with adhesion characterization of single layer tetravinylsilane films. The plasma polymerized thin films were prepared under steady-state deposition conditions on polished silicon wafers using plasma-enhanced chemical vapor deposition. The surface properties of the films were been characterized by different scanning probe microscopy methods and nanoindentation techniques such as conventional depth-sensing nanoindentation and load-partial-unload (cyclic) nanoindentation. While, the nanoscratch test was used to characterize the film adhesion properties. Single layer films prepared at different deposition conditions were characterized with respect to surface morphology and mechanical properties (Young’s modulus and hardness). The results of surface morphology, grain analysis, nanoindentation, finite elemental analysis and modulus mapping helped to know the hybrid nature of single layer films that were deposited at higher powers of RF-discharge. A novel approach was used in surface characterization of multilayer film by scanning probe microscopy and nanoindentation. The adhesion behavior of plasma polymer films of different mechanical properties and film thickness were analyzed by normal and lateral forces, friction coefficient, and scratch images obtained by atomic force microscopy.