Experiments about Simple Liquid Flows in Microtubes

The behavior of micro-scale flow is significant for the performance of Micro-Electro-Mechanical- Systems (MEMS) devices. Some experiments about liquid flow through microtubes with diameters about 3similar to20mum are presented here. The liquids used in our experiments include some simple liquids with small molecules, such as non-ion water and several kinds of organic liquids (CCL4, C6H5C2H5 and Isopropanol etc.). The flow rate and the normalized friction cocfficients were measured in micro-flow experimental apparatus. The results show that when the driven pressure varies from 0 to 1Mpa, the flow behaviors in 20mum microtube for both polar and non-polar liquids are in agreement with Hagen-Poiseuille law of the classical theory. It means that N-S equation based on continuous medium still acts well in this case. For higher pressure drop from 1 to 30Mpa, in the microtubes with diameter of 3similar to10mum, the normalized friction coefficients of organic liquids can't keep constant with pressure increases. However the non-ion water reveals different trends.

Flow similariy applied in convection-based tilt sensor

The environment temperature has inevitable effects on property of the convect ion-based tilt sensors. It not only redefines the application, but also prevents the improvement of the sensor performance. Numerical simulation of the fluid flow in the chamber of a sensor was performed and the influence of the environment temperature was studied in this paper. At zero tilt angle, the temperature distribution along the perpendicular line cross the heat source at various environment temperatures was presented. It was found that the flow varied dramatically at different environment temperatures, which would cause the output signal vary accordingly, even when the tilt angle was kept at a constant, because this device works by sensing the change of flow. At the same condition, we present the numerical results when the temperature difference across the heat source and the environment was kept at the same, in those results, it was found that the temperature difference at every point along the perpendicular line cross the heat source keep the same, this result confirms the similarity principle of nature convection. Second, A method of eliminating environment temperature infect on property of convect ion-based tilt sensor, which is based on the theory of flow similarity, is proposed. It was found that a thermal transistance can be piped on the circuit of heat source to compensate the temperature of the heat source. A compensative circuit was specially designed which can keep flow similarity by changing heat source temperature in order to eliminate the influence of environment temperature. The experiment results show that above 70% temperature drift can be eliminated by this compensative circuit.

Quantum optomechanics with silicon nanostructures

Mechanical resonators are the most basic and ubiquitous physical systems known. In on-chip form, they are used to process high frequency signals in every cell phone, television, and laptop. They have also been in the last few decades in different shapes and forms, a critical part of progress in quantum information sciences with kilogram-scale mirrors for gravitational wave detection measuring motion at its quantum limits, and the motion of single ions being used to link qubits for quantum computation.

Optomechanics is a field primarily concerned with coupling light to the motion of mechanical structures. This thesis contains descriptions of recent work with mechanical systems in the megahertz to gigahertz frequency range, formed by nanofabricating novel photonic/phononic structures on a silicon chip. These structures are designed to have both optical and mechanical resonances, and laser light is used to address and manipulate their motional degrees of freedom through radiation pressure forces. We laser cool these mechanical resonators to their ground states, and observe for the first time the quantum zero-point motion of a nanomechanical resonator. Conversely, we show that engineered mechanical resonances drastically modify the optical response of our structures, creating large effective optical nonlinearities not present in bulk silicon. We experimentally demonstrate aspects of these nonlinearities by proposing and observing ``electromagnetically induced transparency'' and light slowed down to 6 m/s, as well as wavelength conversion, and generation of nonclassical optical radiation. Finally, the application of optomechanics to longstanding problems in quantum and classical communications are proposed and investigated.

Applying systematic design: the flight refuelling probe project

This report is a product of close industry-academia collaboration between British Aerospace and the Cambridge Engineering Design Centre (EDC). British Aerospace designs and integrates some of the most complex systems in the world, and its expertise in this field has enabled the company to become the United Kingdom's largest exporter. However, to stay at the forefront of the highly competitive aerospace industry it is necessary to seek new ways to work more effectively and more efficiently. The Cambridge EDC has played a part in supporting these needs by providing access to the methods and tools that it has developed for improving the process of designing mechanical systems. The EDC has gained an international reputation for the quality of its work in this subject. Thus, the collaboration is between two organisations each of whom are leaders in their respective fields. The central aim of the project has been to demonstrate how a systematic design process can be applied to a real design task identified by industry. The task selected was the design of a flight refuelling probe which would enable a combat aircraft to refuel from a "flying tanker". However, the systematic approach, methods and tools described in this report are applicable to most engineering design tasks. The findings presented in this report provide a sound basis for comparing the recommended systematic design process with industrial practice. The results of this comparison would enable the company to define ways in which its existing design process can be improved. This research project has a high degree of industrial relevance. The value of the work may be judged in terms of the opportunities it opens up for positive changes to the company's engineering operations. Several members of the EDC have contributed to the project. These include Dr Lucienne Blessing, Dr Stuart Burgess, Dr Amaresh Chakrabarti, Major Mark Nowack, Aylmer Johnson and Dr Paul Weaver. At British Aerospace special thanks must go to Alan Dean and David Halliday for their interest and the support they have given. The project has been managed by Dr Nigel Upton of British Aerospace during a 3 year secondment to the EDC.

Nanofabrication for On-Chip Optical Levitation, Atom-Trapping, and Superconducting Quantum Circuits

Researchers have spent decades refining and improving their methods for fabricating smaller, finer-tuned, higher-quality nanoscale optical elements with the goal of making more sensitive and accurate measurements of the world around them using optics. Quantum optics has been a well-established tool of choice in making these increasingly sensitive measurements which have repeatedly pushed the limits on the accuracy of measurement set forth by quantum mechanics. A recent development in quantum optics has been a creative integration of robust, high-quality, and well-established macroscopic experimental systems with highly-engineerable on-chip nanoscale oscillators fabricated in cleanrooms. However, merging large systems with nanoscale oscillators often require them to have extremely high aspect-ratios, which make them extremely delicate and difficult to fabricate with an "experimentally reasonable" repeatability, yield and high quality. In this work we give an overview of our research, which focused on microscopic oscillators which are coupled with macroscopic optical cavities towards the goal of cooling them to their motional ground state in room temperature environments. The quality factor of a mechanical resonator is an important figure of merit for various sensing applications and observing quantum behavior. We demonstrated a technique for pushing the quality factor of a micromechanical resonator beyond conventional material and fabrication limits by using an optical field to stiffen and trap a particular motional mode of a nanoscale oscillator. Optical forces increase the oscillation frequency by storing most of the mechanical energy in a nearly loss-less optical potential, thereby strongly diluting the effects of material dissipation. By placing a 130 nm thick SiO₂ pendulum in an optical standing wave, we achieve an increase in the pendulum center-of-mass frequency from 6.2 to 145 kHz. The corresponding quality factor increases 50-fold from its intrinsic value to a final value of Q_m = 5.8(1.1) x 10⁵, representing more than an order of magnitude improvement over the conventional limits of SiO₂ for a pendulum geometry. Our technique may enable new opportunities for mechanical sensing and facilitate observations of quantum behavior in this class of mechanical systems. We then give a detailed overview of the techniques used to produce high-aspect-ratio nanostructures with applications in a wide range of quantum optics experiments. The ability to fabricate such nanodevices with high precision opens the door to a vast array of experiments which integrate macroscopic optical setups with lithographically engineered nanodevices. Coupled with atom-trapping experiments in the Kimble Lab, we use these techniques to realize a new waveguide chip designed to address ultra-cold atoms along lithographically patterned nanobeams which have large atom-photon coupling and near 4π Steradian optical access for cooling and trapping atoms. We describe a fully integrated and scalable design where cold atoms are spatially overlapped with the nanostring cavities in order to observe a resonant optical depth of d₀ ≈ 0.15. The nanodevice illuminates new possibilities for integrating atoms into photonic circuits and engineering quantum states of atoms and light on a microscopic scale. We then describe our work with superconducting microwave resonators coupled to a phononic cavity towards the goal of building an integrated device for quantum-limited microwave-to-optical wavelength conversion. We give an overview of our characterizations of several types of substrates for fabricating a low-loss high-frequency electromechanical system. We describe our electromechanical system fabricated on a Si₃N₄ membrane which consists of a 12 GHz superconducting LC resonator coupled capacitively to the high frequency localized modes of a phononic nanobeam. Using our suspended membrane geometry we isolate our system from substrates with significant loss tangents, drastically reducing the parasitic capacitance of our superconducting circuit to ≈ 2.5$ fF. This opens up a number of possibilities in making a new class of low-loss high-frequency electromechanics with relatively large electromechanical coupling. We present our substrate studies, fabrication methods, and device characterization.

Theoretical investigations of experimental gravitation

This thesis has two basic themes: the investigation of new experiments which can be used to test relativistic gravity, and the investigation of new technologies and new experimental techniques which can be applied to make gravitational wave astronomy a reality.

Advancing technology will soon make possible a new class of gravitation experiments: pure laboratory experiments with laboratory sources of non-Newtonian gravity and laboratory detectors. The key advance in techno1ogy is the development of resonant sensing systems with very low levels of dissipation. Chapter 1 considers three such systems (torque balances, dielectric monocrystals, and superconducting microwave resonators), and it proposes eight laboratory experiments which use these systems as detectors. For each experiment it describes the dominant sources of noise and the technology required.

The coupled electro-mechanical system consisting of a microwave cavity and its walls can serve as a gravitational radiation detector. A gravitational wave interacts with the walls, and the resulting motion induces transitions from a highly excited cavity mode to a nearly unexcited mode. Chapter 2 describes briefly a formalism for analyzing such a detector, and it proposes a particular design.

The monitoring of a quantum mechanical harmonic oscillator on which a classical force acts is important in a variety of high-precision experiments, such as the attempt to detect gravitational radiation. Chapter 3 reviews the standard techniques for monitoring the oscillator; and it introduces a new technique which, in principle, can determine the details of the force with arbitrary accuracy, despite the quantum properties of the oscillator.

The standard method for monitoring the oscillator is the "amplitude- and-phase" method (position or momentum transducer with output fed through a linear amplifier). The accuracy obtainable by this method is limited by the uncertainty principle. To do better requires a measurement of the type which Braginsky has called "quantum nondemolition." A well-known quantum nondemolition technique is "quantum counting," which can detect an arbitrarily weak force, but which cannot provide good accuracy in determining its precise time-dependence. Chapter 3 considers extensively a new type of quantum nondemolition measurement - a "back-action-evading" measurement of the real part X₁ (or the imaginary part X₂) of the oscillator's complex amplitude. In principle X₁ can be measured arbitrarily quickly and arbitrarily accurately, and a sequence of such measurements can lead to an arbitrarily accurate monitoring of the classical force.

Chapter 3 describes explicit gedanken experiments which demonstrate that X₁ can be measured arbitrarily quickly and arbitrarily accurately, it considers approximate back-action-evading measurements, and it develops a theory of quantum nondemolition measurement for arbitrary quantum mechanical systems.

In Rosen's "bimetric" theory of gravity the (local) speed of gravitational radiation v_g is determined by the combined effects of cosmological boundary values and nearby concentrations of matter. It is possible for v_g to be less than the speed of light. Chapter 4 shows that emission of gravitational radiation prevents particles of nonzero rest mass from exceeding the speed of gravitational radiation. Observations of relativistic particles place limits on v_g and the cosmological boundary values today, and observations of synchrotron radiation from compact radio sources place limits on the cosmological boundary values in the past.

Modelagem da Dinâmica do Sistema de Controle de Lastro de uma Plataforma Semisubmersível.

É descrita a modelagem, para controle, da dinâmica de uma plataforma semisubmersível com seis graus de liberdade. O modelo inclui os efeitos dos tanques de lastro como forças e momentos, assim como a dinâmica da plataforma. Os parâmetros do sistema foram obtidos das características da plataforma e de resultados experimentais obtidos com uma plataforma semisubmersível de dimensões reduzidas. O desenvolvimento de uma metodologia e de um software capazes de determinar o volume submerso e o centro de empuxo de uma estrutura com geometria complexa foram pontos determinantes nessa Dissertação, tendo em vista a complexidade do processo e as importâncias desses parâmetros para o desenvolvimento do modelo. A linearização do modelo permitiu a elaboração de uma estratégia de controle capaz de estabilizar a plataforma mesmo em condições iniciais distantes do equilíbrio. As equações que descrevem o movimento da plataforma nos graus de liberdade vertical, jogo e arfagem foram desenvolvidas. A realocação dos polos e um observador de estado foram utilizados com o objetivo de melhorar o controle do sistema.

Superconducting micro-bearings

This paper presents research into superconducting Micro-Bearings for MEMS systems. Advanced silicon processing techniques developed for the Very Large Scale Integration (VLSI) industry have been exploited in recent years to enable the production of micro-engineered moving mechanical systems. These devices commonly known as Micro-ElectroMechanical Systems (MEMS) have many potential advantages. In many respects the effect of scaling a machine from macro-sized to micro-sized are either neutral or beneficial. However in one important respect the scaling produces a severely detrimental effect. That respect is in the tribology and the subsequent wear on the high speed rotating machines. This leads to very short device lifetimes. This paper presents results obtained from a MEMS motor supported on superconducting bearings. The bearings are self-positioning, relying on, the Meissner effect to provide a levitation force which moves the rotor into position and flux pinning to provide stability thereafter. The rotor is driven by a simple electrostatic type motor in which photo resist is used to pattern the motor poles directly onto the rotor. © 2005 IEEE.

Tribological properties of mems materials measured on a small-scale device

Micro-electro-mechanical systems, MEMS, is a rapidly growing interdisciplinary technology within the general field of Micro-Systems Technology which deals with the design and manufacture of miniaturised machines with major dimensions at the scale of tens, to perhaps hundreds, of microns. Because they depend on the cube of a representative dimension, component masses and inertias rapidly become small as size decreases whereas surface and tribological effects, which often depend on area, become increasingly important. Although MEMS components and their areas of contact are small, tribological conditions, measured by contact pressures or acceptable wear rates, are demanding and technical and commercial success will require careful measurement and precise control of surface topography and properties. Fabrication of small numbers of MEMS devices designed to test potential material combinations can be prohibitively expensive and thus there is a need for small scale test facilities which mimic the contact conditions within a micro-machine without themselves requiring processing within a full semiconductor foundry. The talk will illustrate some initial experimental results from a small-scale experimental device which meets these requirements, examining in particular the performance of Diamond-Like-Carbon coatings on a silicon substrate. Copyright © 2005 by ASME.

Prognosis of underground structures deterioration based on in-situ measurements

The stability of the underground structure is very important not only from the point of view of the structure itself, but also from the point of view of other structures. Therefore, the evaluation of the process of deterioration can help us very much. In the first part of the paper the ageing of the structures in the scope of their life cycle will be described. The whole process of deterioration is important but limited to certain time intervals and is able to give signals about changes in macro-scale. The second part of the paper is focused on the adaptation of new methods: micro technology of monitoring - such as MEMS (Micro Electrical Mechanical Systems) and wireless technologies for data transfer. It is obvious that such new technologies have to be assessed for the ability to deliver data continuously and for their safety and solidity. At the end of the paper the application of the measurements on the Prague metro's lining is mentioned. © 2007 Taylor & Francis Group.

Improved infrared thermal imaging of a CMOS MEMS device

We report a technique which can be used to improve the accuracy of infrared (IR) surface temperature measurements made on MEMS (Micro-Electro-Mechanical- Systems) devices. The technique was used to thermally characterize a SOI (Silicon-On-Insulator) CMOS (Complementary Metal Oxide Semiconductor) MEMS thermal flow sensor. Conventional IR temperature measurements made on the sensor were shown to give significant surface temperature errors, due to the optical transparency of the SiO 2 membrane layers and low emissivity/high reflectivity of the metal. By making IR measurements on radiative carbon micro-particles placed in isothermal contact with the device, the accuracy of the surface temperature measurement was significantly improved. © 2010 EDA Publishing/THERMINIC.

Experimental evidence of flutter and divergence instabilities induced by dry friction

Flutter and divergence instabilities have been advocated to be possible in elastic structures with Coulomb friction, but no direct experimental evidence has ever been provided. Moreover, the same types of instability can be induced by tangential follower forces, but these are commonly thought to be of extremely difficult, if not impossible, practical realization. Therefore, a clear experimental basis for flutter and divergence induced by friction or follower-loading is still lacking. This is provided for the first time in the present article, showing how a follower force of tangential type can be realized via Coulomb friction and how this, in full agreement with the theory, can induce a blowing-up vibrational motion of increasing amplitude (flutter) or an exponentially growing motion (divergence). In addition, our results show the limits of a treatment based on the linearized equations, so that nonlinearities yield the initial blowing-up vibration of flutter to reach eventually a steady state. The presented results give full evidence to potential problems in the design of mechanical systems subject to friction, open a new perspective in the realization of follower-loading systems and of innovative structures exhibiting 'unusual' dynamical behaviors. © 2011 Elsevier Ltd.