摘要： A fluid control system is analysed while operating in a vibrating environment. The introduction and transmission of noise signals in the way of unwanted pressures are examined for passive transmission line elements and an active f lapppr-nozzle control valve when subjected to environmental random or periodic translational vibrations. Methods are presented for predicting the levels and frequencies of induced pressures using distributed and lumped parameter techniques, including some damping effects. Analytic results evalu- ated with the help of a digital and analog computer are presented along with experimental data obtained for vibrating pneumatic trans- mission lines and for a small pneumatic control valve. Also included is a procedure for testing a given system's susceptibility to vibra- tion induced noise sources. It is found that pressure peaks proportional to the fluid density, speed of sound in the fluid, and degree of excitation are generated in transmission lines over a wide band of frequencies. The peaks occur at the system resonant frequencies, and are due to induced fluid flow caused by pipe boundary nonunif ormities (bends and area changes) moving relative to the fluid. The noise signals are excited by either longitudinal or transverse piping vibrations making the system susceptible to noise introduction regardless of its orienta- tion with respect to the vibrating field. Noise is introduced into the control valve by means of the vibrating supply line, inertial forcing of the valve flapper, and for high pressure systems, by vibrations of the transmission line to the load. The greatest noise transmission takes place at low frequencies and near the flapper resonance. Force feedback by means of a bellows arrangement decreases the amplitudes at the lower frequencies, but reinforces those near the flapper resonance and can cause noise power amplification.

摘要： As manufacturing equipment evolve to higher speed and require high precision operations, the impact of environmental changes on machine accuracy becomes critical. Due to thermal expansion, the structure of the machine can change when ambient temperature varies. When the airflow in the laboratory changes, this also alters the operator's thermal comfort. Either the change in machine structure or operator comfort can ultimately affect machine accuracy. The manufacturing industry is currently using heating, ventilation, and air-conditioning (HVAC) systems to regulate the temperature of the working environment. However, since conventional HVAC systems determine whether to activate the HVAC system by collecting the temperature difference around the thermostats, this situation delays air activation time and misses the optimal time to change the factory workshop's internal temperature. This not only fails to ensure the accuracy of high-precision equipment, but also causes energy waste, so an accurate method of monitoring the indoor environment is beneficial to the development of green manufacturing and smart manufacturing. This research uses computational fluid dynamics (CFD) techniques to simulate thermal and airflow distribution in three controlled experiments in the S3 laboratory at the University of South Florida. The experiments were conducted to investigate the changes in temperature and airflow throughout the laboratory influenced by the access of machine operators, computer numerical control (CNC) machine start-up and shutdown, seasonal changes, and the opening and closing of the laboratory door. This experiment is conducted to verify the accuracy of the simulation results and investigate the effects of temperature changes and airflow changes on the thermal deformation of the CNC machine. The average percentage error of the temperature for the three control experiments varied from 0.08% to 0.15%. The error range of the airflow velocity varied from 0 m/s to 0.65 m/s.

摘要： Particle-laden flow in a microchannel resulting in aggregation of microparticles was investigated to determine the dependence of the cluster growth rate on the following parameters: suspension void fraction, shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster was found to increase linearly with suspension void fraction, and to obey a power-law relationships with shear strain rate as S^0.9 and channel-height to particle-diameter ratio as (h/d)^-3.5. Ceramic liposomal nanoparticles and silica microparticles were functionalized with antibodies that act as targeting ligands. The bio-functionality and physical integrity of the cerasomes were characterized. Surface functionalization allows cerasomes to deliver drugs with selectivity and specificity that is not possible using standard liposomes. The functionalized particle-target cell binding process was characterized using BT-20 breast cancer cells. Two microfluidic systems were used; one with both species in suspension, the other with cells immobilized inside a microchannel and particle suspension as the mobile phase. Effects of incubation time, particle concentration, and shear strain rate on particle-cell binding were investigated. With both species in suspension, the particle-cell binding process was found to be reasonably well-described by a first-order model. Particle desorption and cellular loss of binding affinity in time were found to be negligible; cell-particle-cell interaction was identified as the limiting mechanism in particle-cell binding. Findings suggest that separation of a bound particle from a cell may be detrimental to cellular binding affinity. Cell-particle-cell interactions were prevented by immobilizing cells inside a microchannel. The initial stage of particle-cell binding was investigated and was again found to be reasonably well-described by a first-order model. For both systems, the time constant was found to be inversely proportional to part

摘要： Electrokinetics involves the study of liquid or particle motion under the action of an electric field; it includes electroosmosis, electrophoresis, dielectrophoresis, and electrowetting, etc. The applications of electrokinetics in the development of microfluidic devices have been widely attractive in the past decade. Electrokinetic devices generally require no external mechanical moving parts and can be made portable by replacing the power supply by small battery. Therefore, electrokinetic based microfluidic systems can serve as a viable tool in creating a lab-on-a-chip (LOC) for use in biological and chemical assays. Here we present our works of electrokenitic based mixing and separation in microfluidics systems. Firstly, we present a novel fast micromixer of quasi T-channel with electrically conductive sidewalls and some newly observed phenomena on mixing process. The sidewalls of the microchannel can be either parallel or non-parallel with an angle. The mixing behaviors in the micromixer with different angles between the two electrodes located at the sidewalls are studied in terms of velocity and scalar concentration distributions. It is found that mixing can be enhanced rapidly at a small angle about 5 between the two electrode sidewalls even at low AC voltage, compared with that in parallel sidewalls. The effectiveness of several parameters were explored for the further enhancement of the fluid mixing, including conductivity gradient, AC electric flied frequency, applied voltage, AC signal phase shift between the electrodes, etc. The results reveal that the mixing is the stronger under high conductivity gradient, low frequency, high voltage and 180 signal phase shift between the two electrodes. Fast mixing under high AC frequency can be achieved in this quasi T-channel micromixer as well. The most important observation is that for the first time turbulence can be achieved under AC electrokinetic forcing at low Reynolds number in the order of 1 in this novel des

摘要： The objective of this research was to examine the effects of small-scale fluid motion on the kinetic behavior and some key physiological aspects of Dunaliella primolecta Butcher (D. primolecta / Dunaliella). D. primolecta, a fast growing microalga, is a promising organism for alternative energy production because of its capability to accumulate significant amount of "lipids", a major prerequisite for commercial production of microalgal oil-derived biofuel. For kinetic response studies of Dunaliella, flow visualization and quantification techniques such as Particle Image Velocimetry (PIV) and Digital Holographic microscopy were employed. The two-dimensional PIV results showed that Dunaliella were influenced by the fluid flow as soon as the local (or ambient) flow velocities surrounding the cells exceeded the individual (flow subtracted) swimming velocity of Dunaliella. Further inspection of the swimming characteristics of Dunaliella under shear flow in a three-dimensional holography revealed that Dunaliella preferred to swim cross-stream (i.e. also the direction of local vorticity) when the shear flow exceeded a critical value, and this resulted in Dunaliella dispersing in a thin two-dimensional horizontal layer. The cell body rotation was absent during this display in shear flow, although the cell body rotation was evident while swimming in stagnant fluid. A physical model was developed that provided a possible explanation for the cell orienting and swimming in the cross-stream direction in a shear flow while cell body remained irrotational. The experimental swimming data also showed good agreement with the computational results. In order to investigate the biochemical composition and some physiological aspects in Dunaliella under different flow conditions, a laboratory bioreactor equipped with speakers was utilized. The fluid flow velocities in the proximity of the cells generated by the speaker bioreactor are observable in natural water ecosystems. The results sho

摘要： Electrowetting-on-dielectric (EWD) digital microfluidics is a droplet-based fluid han- dling technology capable of radically accelerating the pace of genome engineering re- search. EWD-based laboratory-on-chip (LoC) platforms demonstrate excellent per- formance in automating labor-intensive laboratory protocols at ever smaller scales. Until now, there has not been an effective means of gene transfer demonstrated in EWD microfluidics platforms. This thesis describes the theoretical and experimen- tal approaches developed in the demonstration of an EWD-enabled electrotrans- fer device. Standard microfabrication methods were employed in the integration of electroporation (EP) and EWD device architectures. These devices enabled the droplet-based bulk transformation of E. coli with plasmid and oligo DNA. Peak on- chip transformation efficiencies for the EP/EWD device rivaled that of comparable benchtop transformation protocols. Additionally, ultrasound induced in-droplet mi- crostreaming was developed as a means of improving on-chip electroporation. The advent of electroporation in an EWD platform offers synthetic biologists a reconfig- urable, programmable, and scalable fluid handling platform capable of automating next-generation genome engineering methods. This capability will drive the discov- ery and production of exotic biomaterials by providing the instrumentation necessary for rapidly generating ultra-rich genomic diversity at arbitrary volumetric scales.

摘要： Alternating current (AC) electric signal has been widely applied in microfluidic systems to induce AC electrokinetic behavior. AC electrokinetic phenomena including AC electrophoresis, AC dielectrophoresis, AC electroosmosis flow and AC electrothermal flow are widely applied in (bio)particle sorting, separation and concentration and micropumps. However, numbers of non-ideal AC electrokinetic behaviors have been reported: human erythrocyte deformation in AC dielectrophoresis system has been observed; flow reversal in AC electroosmosis flow pumps has also been reported. In this dissertation, a systematic study on human erythrocyte crenation in AC dielectrophoresis system was firstly conducted. Multiple possible physical mechanisms inducing cell crenation including temperature, temperature jump, pH, shear force and osmotic pressure was examined. pH change and osmotic pressure change induced by ionic concentration change was attributed as mechanisms induced cell crenation. Such pH change and ionic concentration gradient in AC non-uniform electric fields were then further studied. pH change was detected using Fluorescein sodium salt in sodium chloride solution at relative frequency ~5 to 25 times to electrode charging frequency. Time, spatial, frequency and peak-to-peak potential dependencies have been examined on such pH change and pH gradient. Ion concentration behavior was detected by using ionized FITC molecule as fluorescing ion dissolved in inert solvent methanol. Electrode surface is also coated with HfO 2 dielectric layer to minimize effect from electrochemical reaction on FITC emission intensity. Time, spatial, frequency and peak-to-peak potential dependencies have also been examined on ion concentration change and ion concentration gradient. Both pH change and ion concentration change have been observed under high relative AC frequency.

摘要： Implosion is the sudden inward collapse of a submerged structure caused by hydrostatic loading. Confined implosion is characterized by a surrounding structure that significantly effects the flow of fluid around the collapsing volume. The goal of this work is to further understand the physics of collapsing volumes in confined environments. To do so, multiple studies are conducted, each exploring a portion of the parameter space. The first chapter of this work utilizes a unique facility to perform a comprehensive experimental study investigating the implosion of thin, aluminum cylinders with the addition of flow restriction. These experiments take place inside a large pressure vessel and utilize high speed photography, dynamic pressure sensors, and Digital Image Correlation. The results of this work show that by changing the size of the open end, referred to as the flow area ratio, there can be a significant effect on the structural deformations and implosion severity. The other chapters explore parameters including flow restriction, failure mode, and air bubble parameters. In these chapters, additional information is in gained in developing an understanding how these parameters effect the resulting pressure pulses and fluid motion.

关键词： 微流体系统   微流量传感器   Lamb波   microfluidic system   microflow sensor   Lamb wave  

摘要： 为提高微流体系统中的流量检测灵敏度,增大动态检测范围,实现温度补偿,提出了一种基于Lamb波的压差式微流量传感系统。该传感系统主要由两个Lamb波压力传感器和微通道组成,它利用Lamb波薄膜内应力的敏感特性,以频率计量的方式间接测量微通道两端的压力差;并采用双Lamb波压力传感器构成差动式测量结构进行温度补偿。对长20 mm,宽1 mm,高50 μm的微通道进行了流量测试实验,结果表明:在流量测试范围内,微通道两端的频率差与流量基本呈线性变化,其线性相关系数为0.999 9;在微流量传感器未进行优化的前提下,最小检测量为0.627 μL/s。关键词

摘要： The goal of this work was to construct a comprehensive, efficient and accurate three- dimensional (3-D) computational tool that could be used to improve our understanding of the physical processes of water circulation, transport and mixing in lakes. The availability of a relatively large number of three-dimensional flow solvers suggested at the outset that there was a more pressing need for formulating a methodology by which such codes could be tested and evaluated, rather than the development of a new code. That methodology, once developed, was applied to compare a finite difference and a finite element flow solver for their suitability for applications in lakes. The 3-D semi-implicit leapfrog-trapezoidal finite difference solver was selected as the more suitable on the basis of the results of the test methodology. The model was extensively modified to incorporate features needed for the accurate simulation of lake hydrodynamic phenomena. The extended model uses spatially and temporally variable wind fields and calculates mixing coefficients with a high-order turbulence closure model. A transport model for temperature was implemented, which uses flux limiters and directional splitting methods to discretize the 3-D advection operator and calculates heat fluxes at the free surface based on meteorological information and prognostic variables. A stand-alone Lagrangian particle-tracking model was also developed to visualize circulation patterns and simulate the transport of particulate matter. The model was applied to two lakes of very contrasting internal dynamics. The first, Clear Lake, is a multi-basin, shallow, polymictic and eutrophic lake in northern California. The second, Lake Tahoe, is a deep monomictic and oligotrophic lake straddling the border between California and Nevada. The internal dynamics of Clear Lake is characterized by a cycle of setup and relaxation of horizontal density gradients controlled by strong, periodic wind events. The model was used in C