The research carried out in this thesis describes the processing of liquids and ceramic suspensions, having a viscosity >100mPa s, using electrostatic atomization, mainly in the stable cone-jet mode. Electrostatic atomization, also called electrospraying, refers to a process where a liquid or a suspension is made to flow through a needle. The liquid or suspension is subjected to a high voltage maintained between the needle and a ground electrode. Two major physical properties, namely electrical conductivity and viscosity, affect electrostatic atornization in the stable cone-jet mode and the investigations described in this thesis focussed on the latter. Firstly, a set of liquid mixtures were prepared using distilled water and glycerol. The dc electrical conductivity of these mixtures were kept constant and the viscosity was varied. The mixtures were subjected to electrostatic atornization and in each case the mode of atornization, the cone/jet characteristics and relic sizes were studied as a function of viscosity. The effect of applied voltage on the conejet mode electrostatic atornization of glycerol having a viscosity of 1338mPa s was also investigated. Secondly, the possibilities of electrostatically atomizing ceramic suspensions were studied in detail. Several alumina suspensions were used including one containing a high volume fraction of solids (20 vol. % - the highest filler loading attempted to date using any jet-based processing route). Applied voltage - flow rate - atornization mode maps were constructed for this suspension incorporating even pico-flow rate regimes. This is a new input into the aerosol science and engineering literature. This section also highlights the importance of controlling the applied voltage and flow rate as these parameters affect the jet diameter and relic/droplet size generated. The effect of the geometry of the ground electrode used for electrostatic atornization was also investigated. In particular, the use of a point-like ground electrode was studied for the very first time. The third and most innovative facet of this research was the discovery of ceramic electrostatic atornization printing (CEAP) and the use of electrostatic atornization to produce ceramic foams. In CEAP a point-like ground electrode is used to focus the spray which was printed as characters, collection of characters and single tracks. This investigation was extended to explore the printing of multiple tracks produced with the aid of several needles and ground electrodes which worked simultaneously. A ring shaped ground electrode was used to electrospray ceramic droplets onto a polyurethane template and this paved the way for the development of a new method to prepare open-cell ceramic foams with a very high porosity. This method was extended to prepare ceramic structures and complex components.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 239-242. / Ph.D.

Microfluidic device construction uses certain critical structures throughout many different applications. The valve structure remains one of the primary structures that present a barrier to miniaturization and portability. The extensive support devices required to power common microfluidic valves remove a significant amount of freedom from microfluidic device design. Moving to electrostatic methods of actuation could reduce the overall footprint of the microfluidic valve. This thesis covers three concept prototypes. Concept I presents an attempt at inlaying gold electrodes into polydimethylsiloxane substrates. Concept II attempts to use liquid silver injected into channels as electrode materials. Concept III uses aluminum sputtering to fabricate valve electrodes. Each device encountered complications during fabrication which led to improved fabrication guidelines for future devices. Designing and fabricating these concept devices required the development of several new processes in the clean room, including RIE Plasma bonding, PDMS sputtering techniques, and multilayer PDMS thin film fabrication. The PDMS sputtering technique in particular allows profilometry measurement of PDMS surfaces without risk of damaging the profilometer tip, a development that could allow for much more control over PDMS film thicknesses in future projects.

Electrical insulation under high voltage can eventually fail, causing critical damage to electronics. Such electrostatic discharge (ESD) is the primary source of anomalies or failures on spacecraft due to charged particles from the Sun or planetary radiation belts accumulating in spacecraft insulators. Highvoltage direct current power distribution is another example of a growing industry that needs to estimate the operational lifetime of electrical insulation. My research compares laboratory tests of ESD events in common insulating materials to a physics-based model of breakdown. This model of breakdown is based on the approximation that there are two primary types of defects in structurally amorphous insulators. One of the two defect modes can switch on and off depending on the material temperature. This dual-defect model can be used to explain both ESD and less-destructive transient partial discharges. I show that the results of ESD tests agree reasonably well with the dual defect model. I also show that transient partial discharges, which are usually ignored during ESD tests, are closely related to the probability of catastrophic ESD occurring. Since many partial discharges are typically seen during one ESD test, this relationship suggests that the measurements of partial discharges could accelerate the testing needed to characterize the likelihood of ESD in insulating materials.

Dust control is a very significant issue in underground coal mining. The benefits of reducing dust levels will be a lesser risk of lung disease to coal miners, improved working conditions and a reduced risk of dust explosions. Coal dust is commonly suppressed by water sprays but suppression efficiency is not high because dust tends to travel in the air flow round the water droplets rather than being captured by them. If water sprays are electrostatically charged, then a significant improvement in dust suppression efficiency may be achieved. Of the three principal droplet charging mechanisms, i.e. corona charging, induction charging and contact charging, corona charging is the most widely used in many industrial fields including dust suppression, However, it requires a high applied voltage, ranging from thousands to more than a hundred thousand volts, depending on the geometry of the charging equipment. Induction charging has been used in agricultural spraying since Law (1978) developed an embedded-electrode induction charging spraying nozzle. This nozzle provides a compact, inexpensively fabricated droplet charger and, reduces design requirements on size and output voltage (of the order of 1000 volts). It also reduces the potential for mechanical damage, misalignment and personnel hazard. In order to evaluate the effectiveness of dust suppression, either the charge on individual droplets or the charge-to-mass ratio of water sprays needs to be known. However, the parameters which control the charge applied to water and the charging rate have been unsolved theoretically for any charging mechanism. The existing theories for the induction-charged and air-atomising a liquid jet have been found to be inadequate. And there is no theory available for corona charging of the droplets produced with a pneumatic nozzle in order to predict the spray charge level or the spray charge-to-mass ratio. In view of this situation, mathematical models have been developed in this thesis for both the corona and induction charging mechanisms. During the development of the theories, it has been assumed that for corona charging, that the jet is disintegrated into droplets and the droplets are then charged; for induction charging, that the jet is first charged and the charged jet is then disintegrated into charged droplets. The Sauter mean diameter of the sprays, D32 , plays an important role in linking the individual droplet charge to the spray charge-to-mass ratio for both charging mechanisms. The developed theories are general models suitable for any liquid with both corona and induction charging. Theoretical calculations for the spray charge-to-mass ratio, individual droplet charge and the ratio of droplet charge to the Rayleigh charge limit have been presented for almost all of the influencing electrical and mechanical parameters such as applied voltage, air flowrate, liquid flowrate, liquid conductivity, liquid dielectric constant, nozzle dimensions, cylindrical electrode dimensions, and fluid parameters, for example, density, viscosity and surface tension. In the calculation for corona charging of droplets, the effect of the droplets on corona current and corona-onset voltage has been assessed for first time. The introduction of the Sauter mean diameter of the sprays, D32 , makes the assessment possible. Theoretical calculations for induction charging of liquid jets have shown that provided liquids have a conductivity value higher than the critical value, s = - 10 4 S/m, then they can be charged satisfactorily by the induction charging method. Among all of the influencing parameters, the electrical and mechanical parameters determine the charging rate and the water spray charge level. The suitability of employing these two charging mechanisms to dust suppression in coal mine has been evaluated based on the spray charge level, safety issues and the simplicity or otherwise of the equipment. The induction charging method was considered to have advantages over its corona charging counterpart, and has been chosen for charging the water sprays in the experiment program. Water has a conductivity of s = - 10 2 S/m, higher than the critical value, s = - 10 4 S/m. Based upon theoretical considerations, it is concluded that water is an appropriate liquid for corona charging, based on its dielectric constant, and for induction charging, based on its conductivity. In order to facilitate the testing of electrostatically charged water spray cloud parameters, a spray charger/collector was designed and constructed by others and a computerised data acquisition system has been employed. According to the theory developed for induction charging, the optimum length of the charging electrode has been analysed based upon the assumption that water jet is first charged and then the charged jet is disintegrated into charged droplets by the high pressure air. An experimental program examined the dependence of spray current upon four parameters: air flowrate, water flowrate, applied voltage and jet diameter. The experiments have shown that the induction-charged air-atomising nozzle used in the experiment is able to impart a significant charge into the water sprays. The spray charge-to-mass ratio calculated based upon the measured spray current demonstrates the same characteristics as predicted by theory: increasing with air flowrate, decreasing with water flowrate, increasing with applied voltage to a peak value then decreasing with further increase in the voltage, and increasing with jet diameter. A successful interpretation of an important phenomenon in the inductioncharged air-atomising a water jet, that spray charge-to-mass ratio and spray current increase with air pressure (or air flowrate) and decrease with increasing water flowrate, has been achieved based on the theories developed in this thesis. This phenomenon occurs because increasing air flowrate and/or decreasing water flowrate leads to a higher velocity of jet flowing through the induction electrode. However, when water flowrate becomes very small, a decrease in spray current with increasing air pressure (or flowrate) may be caused both by jet breakup inside the electrode and by contraction of the jet. In order to verify the theory, a preliminary comparison of experimental data with theoretical predictions employing a constant kic in the air-jet interaction coefficient a which was assumed to be 0.7 has shown a general agreement. However, the value of kic appears to be related to jet diameter, air/water mass ratio and applied voltage. An empirical equation for kic has then been formulated based on the experimental data for the spray charge-to-mass ratio. Finally a comparison of experimental results with theoretical predictions using the formulated kic shows an improved agreement. It is concluded that the induction-charged air-atomising nozzle has a potential application in dust suppression in coal mines, as the voltage required to charge water sprays is only 1000 ~ 1200 volts, and that the theory developed for induction charging of water sprays can be used to guide laboratory investigations and design processes for dust suppression and other industrial applications which might employ the electrostatic charging of liquid sprays.

Doxorubicin (DOX) and Pluronic-PAA interaction was investigated using isothermal titration calorimetry (ITC). DOX/polymer interaction is governed primarily by electrostatic interaction. The uptake of DOX results in the formation of insoluble polymer/DOX complex. Addition of salt weakens the interaction of drug and polymer by charge shielding effect between positive ionized amino group on DOX and oppositely charged polymer chains. However high drug-loading capacity in high salt condition implied that self-association property of DOX also play a role in the drug loading process. / Singapore-MIT Alliance (SMA)

Thesis (M.S.)--Ohio University, June, 2005. / Title from PDF t.p. Includes bibliographical references (p. 75-76)

This thesis focuses on pioneering a scalable route to fabricate quantum information devices based upon single InAs/InP quantum dots emitting in the telecommunications wavelength band around 1550 nm. Using metallic gates in combination with nanotemplate, site-selective epitaxy techniques, arrays of single quantum dots are produced and electrostatically tuned with a high degree of control over the electrical and optical properties of each individual quantum dot. Using metallic gates to apply local electric fields, the number of electrons within each quantum dot can be tuned and the nature of the optical recombination process controlled. Four electrostatic gates mounted along the sides of a square-based, pyramidal nanotemplate in combination with a flat metallic gate on the back of the InP substrate allow the application of electric fields in any direction across a single quantum dot. Using lateral fields provided by the metallic gates on the sidewalls of the pyramid and a vertical electric field able to control the charge state of the quantum dot, the exchange splitting of the exciton, trion and biexciton are measured as a function of gate voltage. A quadrupole electric field configuration is predicted to symmetrize the product of electron and hole wavefunctions within the dot, producing two degenerate exciton states from the two possible optical decay pathways of the biexciton. Building upon these capabilities, the anisotropic exchange splitting between the exciton states within the biexciton cascade is shown to be reversibly tuned through zero for the first time. We show direct control over the electron and hole wavefunction symmetry, thus enabling the entanglement of emitted photon pairs in asymmetric quantum dots. Optical spectroscopy of single InAs/InP quantum dots atop pyramidal nanotemplates in magnetic fields up to 28T is used to examine the dispersion of the s, p and d shell states. The g-factor and diamagnetic shift of the exciton and charged exciton states from over thirty single quantum dots are calculated from the spectra. The g-factor shows a generally linear dependence on dot emission energy, in agreement with previous work on this subject. A positive linear correlation between diamagnetic coefficient and g-factor is observed.

No description available.

The contious reduction in size and work voltage of the new generation integrated circuits (ICs) requires the reducction of the thickness of the different layers that make up (especially the gate oxides and levels of isolation between conductors), in order to increase its density and speed of integration, reducing its energy consumption. However, these improvements involve an increase in their sensitivity to external perturbations such as fluctuations in the electricity network, capacitive coupling or electrostatic discharge (ESD). Although there is a wide range of electronic devices designed to protect ICs from such disturbances avoiding destruction (Zener diodes, thyristors, etc.), The continuous reduction of voltage operation and increasing the frequency of work has required a major research effort to adapt the protective devices to the new conditions of operation. The main features that should satisfy any device designed to protect an electronic system are: fast response, low parasitic capacity, driving in low resistance, high absorption capacity of current, low leakage current in reverse, minimum size, low cost, should not interfere in the normal mode of operation of the system that protects and must maintain unchanged its electrical characteristics over time. In high voltage applications, Zener diodes and thyristors are the most used, both in format as a discreet way to the monolithic IC, for protection against ESD phenomena. However, new generations of ICs for mobile applications (portable computers, telecommunications, remote control systems, etc.) Require devices capable of working at low voltage and low energy consumption (in order to maximize the life of batteries ). Under these conditions, the protection of traditional elements are not optimal, so that further protection devices with low voltage and low shooting leakage current in his block state. In this situation, the use of new protective structures based on a process of rupture by emptying (punch-through) improves the characteristics of those based on a break by avalanche (base of the traditional components). Thus, this study aims to analyze, optimize, design and produce new elements of protection by breaking with punch-through, known as Transient Voltage Suppressors (TVS), which improve the performance of Zener diodes in applications from low tension (less than 3 V). Thus, Chapter 1 describes the main electric perturbation and sources that originated, along with a description of its effect on the CIs. It also provides a description of the different existing devices suppressors, with special emphasis on TVS, the main topic for this work. In Chapter 2 presents a study of the vertical TVS based in the punch-through effect, which analyzes the electrical characteristics of its two configurations (TVS 3 layers, TVS 4 layers). It also presents the theoretical model of rupture developed for this type of structures as well as the verification of it through numerical simulations and experimental data. Chapter 3 deals with the design, fabrication and characterization of vertical TVS. We show the technological processes done and the improvements are detailed, demonstrating the superiority of TVS 4 layers respect to the TVS 3 layers and Zener diodes. Chapter 4 presents the first study published on lateral punch-through TVS devices intended to be integrated with the circuitry to protect. The study was conducted for different configurations proposed in technology Bulk Silicon, compared among themselves and choose the configuration that shows better characteristics. This chapter also presents a novel way of using the field plate to reduce the breakdown voltage into the lateral TVS. Finally, and as a line of the future, assessing the feasibility of integrating lateral TVS devices in SOI (Silicon-On-Insulator) substrates. Finally, Chapter 5 shows the manufacturing of lateral TVS. Details the technological process, the design of masks, clean room manufacturing in the characterization and finally, whether technological, using techniques of Reverse Engineering, as electric.