Measurement Of Charge Distribution Research Articles

A Review of Electrostatic Measurement Techniques for Aerosol Drug Delivery to the Lung: Implications in Aerosol Particle Deposition

Electrostatic properties of formulation components play an important role in inhalation products. Suitable measurement of charge distribution will, therefore, lead to better control of inhalation formulation manufacture. Advances in this field have been made in the past few years but, real time, direct techniques still need to be developed further to obtain a precise, accurate and easy to use measurement of electrically charged aerosolised powders. This short review presents an overview of the various techniques present in literature for measurement of charge applicable to inhalation dosage forms.

Measurements of Aerosol Charge and Size Distribution for Graphite, Gold, Palladium, and Silver Nanoparticles

Measurements of Aerosol Charge and Size Distribution for Graphite, Gold, Palladium, and Silver Nanoparticles

Investigation of Electrostatic Properties of Pharmaceutical Powders Using Phase Doppler Anemometry

Electrostatic properties of formulation component materials and blends play an important role in dry powder inhalation (DPI) products. Valid measurement of charge distribution will therefore lead to better control of powder behavior in DPI manufacturing processes. Ultrafine powders are known to have bipolar charge, have nonspherical shapes, and tend to be highly cohesive. Real-time noninvasive techniques need to be developed to obtain a precise and accurate measurement of electrically charged powders, as they aerosolize from a DPI product. How this measure relates to materials behavior throughout the various steps of a manufacturing process, e.g., from drug micronization and blending with lactose to filling dose units, also needs to be addressed. A novel noninvasive technique, which employs the phase Doppler anemometry (PDA) system for simultaneous measurement of size and charge of pharmaceutical powders, is currently being considered. Previous research demonstrated the advantages of this technique in measuring the bipolar charge distribution on a population of liquid aerosols. These findings led to significant improvements in understanding the performance of inhaler formulations, manufacturing processes, and development of new devices for inhaled drug delivery. This paper presents an investigation of electrostatic properties of lactose materials (typically used as a DPI excipient) using the PDA system. PDA calibration was checked using dry polystyrene microspheres, followed by an investigation of different grades of lactose. The PDA technique was used to track the motion of charged particles in the presence of an electric field. The magnitude, as well as the polarity of the particle charge, can be obtained by solving the equation of particle motion combined with the simultaneous measurement of its size and velocity. Results show the capability of the technique to allow real-time charge distribution and size measurement in the control of dry powder attributes that are critical to a better understanding of the manufacturing design space.

Imaging of Surface Charge and the Mechanism of Desorption Electrospray Ionization Mass Spectrometry

Distributions of charge deposited on surfaces in desorption electrospray ionization mass spectrometry (DESI-MS) were investigated using a static charge measurement apparatus, which gives an output voltage proportional to the local surface charge density. By scanning the probe along the surface and taking measurements at fixed intervals, a contour image of relative charge density reflecting the charge distribution on the surface can be plotted. Through the measured charge distribution and the derived charge density gradient, the motion of charged droplets in the DESI experiment can be inferred. Measurements taken under various DESI operating conditions, including spray pressure, angle, flow rate, and sprayer tip-to-surface distance, show that charge is spread over an area of a few square centimeters under typical conditions; effective desorption occurs from a much smaller area (∼1 mm2) of highest charge density. Higher sheath gas pressures and smaller sprayer tip-to-surface distances lead to concentration of charge distribution into a smaller area, whereas smaller spray angles favor charge distribution over a larger area. The appearance of the highest charge density in front of the DESI sprayer tip and near the MS inlet suggests that charged droplets are moved toward the MS inlet by pneumatic forces and by the vacuum suction, in agreement with results of earlier simulations. The present observations are consistent with previous studies using other techniques and support the accepted droplet splashing DESI mechanism.

Imaging of charge spatial density on insulating materials

We describe the measurement of spatial charge distribution, using a new non-invasive technique. This measurement, based on a 16-element array of ultra-high impedance electric field sensors, is capable of producing both quantitative results for the total amount of surface charge present, as well as imaging the charge to produce plots representing spatial charge distribution. We calibrate the measurement against a conventional induction field meter charge measurement which discharges the sample. Further to this, we show that our technique has no discharging effect on the sample and that therefore it is possible to observe the discharging of insulating materials over periods of several days.

Measurement of charge distribution in actin bundles by surface potential microscopy

Bundles of filamentous actin (F-actin) deposited on a gold-plated surface were concurrently imaged using atomic force microscopy (AFM) and surface potential microscopy (SPM). The surface potential was mapped as a function of tip distance to surface using a constant bias potential. There was an uneven spatial distribution of charges detected by SPM, consistent with the segmented topological features shown by AFM of the actin bundles. SPM analysis showed localized changes in surface potential between the axial and transversal sections of the bundles, which are consistent with nonuniform charge distributions of adsorbed salt ions on F-actin.

Suppression effect of surface fluorination on charge injection into linear low density polyethylene

To suppress charge injection from electrodes, direct fluorination using fluorine gas was used for linear low density polyethylene (LLDPE) since it is one of the most effective methods of the polymer surface modification. Surface fluorination of the LLDPE plates was obtained as indicated by attenuated total reflection infrared spectroscopy. Remarkable suppression of charge injection by the surface fluorination was observed by space charge distribution measurements using the pressure wave propagation method. Comparing with the remarkable bipolar charge distribution in bulk of the original LLDPE, there is less space charge in bulk and it mostly exists in the fluorinated surface layers. The possible mechanisms of the charge injection suppression are discussed, one of which, the effect of fluorination on the charge traps in surface layer was investigated by the thermally stimulated discharge technique. The results indicate that fluorination has charge traps in the surface layer remarkably deepened and charges captured in the deep traps can block or shield the further charge injection.

Introduction of the Electrical Next Generation Impactor (eNGI) and Investigation of its Capabilities for the Study of Pressurized Metered Dose Inhalers

To introduce the design of the electrical next generation impactor (eNGI), and validate its proposed function as a method of electrostatic characterization for pressurized metered dose inhaler (pMDI) formulations. Flixotide (fluticasone propionate), ventolin (salbutamol sulphate), and qvar (beclomethasone dipropionate) were used as model pMDIs in this study. At an airflow rate of 30 l/min, five individual actuations of each pMDI were introduced into the electrical low-pressure impactor (ELPI), Next Generation Impactor (NGI), and the eNGI. Charge profiles for each actuation were measured by the ELPI and eNGI, while mass profiles were recorded by the all three impactors. The difference in estimated mass median aerodynamic diameters and geometric standard deviations for all pMDIs using the NGI and eNGI were not found to be statistically significant (p<0.05). The mean charge profiles from the ELPI and eNGI overlap well between 0.54 and 6.61 microm (flixotide and ventolin), and between 0.615 and 11.72 microm (qvar), where the majority of the impacted doses were collected. For the analysis of pMDIs, the eNGI is comparable to the NGI in measuring particle size distribution, while still being comparable to the ELPI in measuring charge distribution.

The role of weathering on fly ash charge distribution during triboelectrostatic beneficiation

Triboelectrostatic beneficiation of coal combustion fly ashes with high-unburned carbon contents can produce low-carbon ash products having value as mineral admixtures and meeting technical requirements for replacing cement in concrete. This capability is a result of establishing bipolar charge on mineral ash versus carbon particles where, typically, unburned carbon attains positive surface charge and ash attains negative surface charge under the tribocharging conditions employed in triboelectrostatic technologies. However, long-term exposure of fly ash to weathering conditions, such as moisture or high humidity, before beneficiation is known to dramatically diminish carbon–ash separation efficiencies. Although experimentation has shown that water soluble surface species can be redistributed on fly ash particles after exposure to moisture, which could affect the extent of charging and polarities, measurement of the actual amount of charge and polarity on particles after weathering exposure versus after removal of surface moisture has not been accomplished. Hence, a new experimental methodology was developed and applied to measure charge distributions on tribocharged ash and carbon particles in a fly ash that had been exposed to weathering conditions for 6 months before and after removal of the surface moisture. Weathered ash particles were found to have an average zero charge, whereas carbon particles attained an average negative charge, opposite of the normal polarity for carbon. Although the extent of uncharged particles decreased and ash particles attained an average negative charge after drying, carbon particles attained only an average zero charge. These changes were reflected in very small increases in carbon–ash separation efficiency, in contrast to previous beneficiation tests in which fly ash drying led to significant increases in carbon–ash separation efficiency. It is suggested that removal of surface moisture in the absence of other processes like surface ion redistribution would beneficially impact carbon–ash triboelectrostatic beneficiation.

Measurement of internal charge distribution in dielectrics using the pulsed electro-acoustic method in non contact mode

We introduce a pulsed electro acoustic (PEA) device enabling space charge measurement inside dielectric films without the need of sample to excitation unit contact. The new device -called open PEA because one face of the film is at a floating potential- has been used to investigate the internal charge of electron beam irradiated dielectrics. Details are given on the system and its calibration for performing quantitative charge measurements. Charge distributions in electron beam irradiated polytetrafluoroethylene (PTFE) films are compared using the classical and the open PEA. Due to the short-circuit condition in the classical PEA, the implanted charges measured using the two systems are drastically different. Surface potential and current measurements performed during irradiation have been used to validate the measurement in the open configuration which is well suited to investigate the behaviour of dielectrics in space environment.

Resolution of direct space charge distribution measurement methods

Spatial resolution is a key parameter for the measurement of any distribution. In the case of space charge distribution measurements, it is difficult to compare technique performances since each technique has its own resolution definition most of the time. In this paper the resolution, in terms of position accuracy and charge discernment, is determined on the basis of a unique definition for the thermal, the pressure-wave- propagation and the electro-acoustic methods and their derived techniques. It is shown that spatial resolution is similar throughout the sample in the case of the pressure- wave-propagation or the electro-acoustic methods, except if attenuation and dispersion of elastic waves are important, but decreases as the charge position inside the sample in the case of thermal method. Elastic wave methods are therefore preferable for a given signal to noise ratio as soon as the sample thickness is larger than twice the sound velocity times the excitation rise time.

Charge-State distributions of heavy ions and nuclear reaction products at the exit from solid targets

Using a stepped-pole broad-range magnetic analyzer, the charge-state distributions of heavy ions have been measured upon their passing through thin carbon and gold foils. A review is presented of works on the charge distribution of heavy ions passing through solid targets and reaction products at the exits from these targets. The measured charge distributions of accelerated ions and ion-induced reaction products at the exit from the targets are compared to the theoretical values. It is shown that the calculated mean charges of heavy ions and reaction products can be used only as estimates.

帯電量分布測定装置を利用したトナー帯電分析

Many types of toner charge spectrometers have been designed because the measurement of toner charge distribution in an electrophotographic development system would be useful in evaluating and optimizing the system. However, some charge spectrometers cannot accurately measure the charge distribution; moreover, it is difficult to collect the toner particles classified by charge. We designed and manufactured a charge spectrometer using electrostatic field and gravity without air flow, which can classify the toner particles into different specific charge groups. The toner particles were analyzed by the particle analyzer measuring the composition and size of toner and additives. The analysis of a single-component toner showed that smaller sized toners with a large amount of additives resulted in a highly charged toner. The analysis method using the charge spectrometer and the particle analyzer together is very useful for studying the mechanism of toner charging and for producing a high-quality toner.

Characteristic of charge accumulation in glass materials under electron beam irradiation

Space charge formation in various glass materials under electron beam irradiation was investigated. The charging of spacecrafts occurs in plasma and radiation environments. In particular, we focused on an accident caused by internal charging in a glass material that was used as the cover plate of a solar panel array, and tried to measure the charge distribution in glass materials under electron beam irradiation using a pulsed electroacoustic (PEA) method. In the case of quartz glass (pure SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), no charge accumulation was observed either during or after the electron beam irradiation. On the contrary, charge accumulation was observed in glass samples containing metal oxide impurities. It is found that the polarity of the observed charges depends on the contents of the impurities. To identify which impurity dominates the polarity of the accumulated charge, we measured charge distributions in several glass materials containing various metal oxide impurities. Furthermore, the dependence of the polarity of accumulated charges on the composition of glass materials is discussed using energy band models

Analysis of the X-ray and time-resolved XUV emission of laser produced Xe and Kr plasmas

A frequency-doubled laser beam of the Nd:glass kilojoule nanosecond LULI2000 facility (1.5 ns duration, 200–400 J energy, 0.53 μm wavelength) was focused on a Xe or Kr gas jet. The plasma was simultaneously diagnosed with X-ray (in the wavelength range of 6–8 Å for Kr and of 12–15 Å for Xe) and time-resolved XUV (20–200 Å) emission spectroscopy. Electron density and temperature as well as the ionization charge were measured by time-resolved Thomson scattering of the heating laser pulse. The spectra are compared with the calculations performed with the NLTE collisional-radiative code AVERROES/TRANSPEC. Best fits of the X-ray and XUV spectra obtained are presented. The measured charge distribution and dynamics is analyzed using the simultaneous Thomson scattering diagnostic.

Local and Holistic Electromagnetic Therapies

Based on decades of experimental evidence an excellent argument can be made for the existence of a fundamental functional relationship between living systems and electromagnetic fields. We have previously hypothesized that this relationship can be expressed in terms of a field vector whose source is the distribution of electric polarization within the system and which has both a phylogenetic and ontogenetic time dependence. Ion cyclotron resonance (ICR)-like magnetic signals have resulted in physiologic changes in many in vitro and in vivo model systems and have been applied medically with success to bone repair and spinal fusion. This type of local ICR-like therapy has recently been broadened into a holistic application following the remarkable discovery that the whole-body bioimpedance is sharply dependent on ICR signals. We relate this observation to the integrated electric polarization vector, in turn a measure of the double layer charge distribution at the cell membrane. This discovery, already being applied to a number of clinical problems, lends strong support to the concept of an overarching electromagnetic framework for living systems.

Pulse Acoustic Technology for Measurement of Charge Distribution in Dielectric Materials for Spacecraft

Recently, some accidents in spacecraft due to charging up by irradiation of charged particles have been reported. Some of them are caused by a surface discharge, which normally takes place in a plasma environment in space. Some others seem to be caused by a discharge due to an accumulation of charge in the bulk of materials in a relatively high-altitude environment. To investigate the charge accumulation in the bulk of materials, the authors have been developing an internal charge measurement system. The internal charge accumulation in dielectric materials under irradiation of artificial radioactive rays is observed using the developed system, which employs the so-called pulsed electroacoustic method and pressure wave propagation method based on pulse acoustic measurement techniques. The developed system is applicable to the measurement of the charge distribution in dielectrics in air atmosphere or vacuum environments under electron beam, proton beam, and gamma ray irradiations. Using the system, we measured bulk charge distributions in polymeric films and glass materials. In this paper, summaries of some typical measurement results are presented following a brief explanation of measurement principles

A preliminary study of space charge distribution measurements at nanometer spatial resolution

The continuous reduction in size of devices, such as integrated circuits or micro-electro-mechanical systems (MEMS), results in the need to control with better and better resolution the materials involved, and in particular the electrical properties of the insulating and semiconducting parts. In this paper we propose an approach applicable to space charge measurement methods for improving the resolution to the nanometer range by using femtosecond laser pulses. It is shown that a resolution of about 60 nm in SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> can be achieved with thermal and pressure wave propagation methods. Concerning the pulsed electro-acoustic method, the interfacial displacement as small as 100 fm can be measured at THz rate

A preliminary study of space charge distribution measurements at nanometer spatial resolution

A preliminary study of space charge distribution measurements at nanometer spatial resolution

Effects of probe numbers and arrangement on the measurement of charge distributions around a rising bubble in a two-dimensional fluidized bed

The charge density distribution around a rising bubble in a two-dimensional fluidized bed was measured using eight induction probes flush with the outside wall of the column and connected to charge amplifiers for recording induced charge signals as bubbles passed by. The charge distribution surrounding the bubble was reconstructed using an iterative linear back projection (LBP) algorithm by assuming that the bubble is symmetrical and the charge around the bubble remains constant as the bubble rises. The results showed that the emulsion phase far from the bubble in a two-dimensional fluidized bed of glass beads was charged negatively, and the charge density decreased gradually toward the bubble-dense phase interface, with a nearly zero charge density inside the bubble. The effects of the number of probes are also investigated. The reconstructed results using both simulated charge distribution and experimental data for different numbers of probes of the same probe diameter of 3 mm showed that increasing the number of probes can improve the reconstruction resolution. The addition of one or two more probes outside the bubble path also increased the reconstruction resolution in the region outside the bubble.