Measurement Of Electrostatic Charge Research Articles

A detailed investigation of N95 respirator sterilization with dry heat, hydrogen peroxide, and ionizing radiation

In the present ongoing pandemic, the N95 respirator is an essential protective barrier to suppress the spread of the SARS-Cov-2 virus and protect the frontline worker from exposure. The N95 respirators are meant for single usage; however, they can be used after sterilization, considering the economy and shortfall in availability. At this juncture, the performance of the respirator after various types of sterilization and usage condition is required to be analyzed in detail. With this motto, this work has proceeded. The respirator’s filtration efficiency (FE), breathing resistance, and quality factor are evaluated for two face velocities (5.8 ± 0.2 and 26.4 ± 0.9 cm/s). Sterilization techniques used here are dry air oven heating at 70–80 ± 3°C for 30 and 60 min, gamma irradiation for cumulative dose 15 and 25 kGy, and soaking in liquid hydrogen peroxide for 30 min. The filtration performance and electrostatic surface charge density are used to determine the facemask’s efficacy after sterilization. The respirator’s physical, chemical, and morphological degradation were investigated using materials area density, microscopic analyses, FTIR, Raman spectroscopy, EPR, and TGA analyses. The highest reduction in filtration efficiency is 29.36 ± 0.49–36.08 ± 1.78% after irradiation due to a reduction in the charge density (71–133%) of the respirator layers. However, the FE does not reduce significantly (0.39 ± 0.52 to −2.46 ± 0.60) for dry air heat and H2O2 sterilization despite a change in charge density (0.4–53%), but there is no direct correlation with FE. Electrostatic charge measurement of the filtration layer is a crucial indicator of FE degradation. Hence, dry air heat and H2O2 soaking are found to be the most suitable sterilization methods. No significant degradation was observed on the physical, chemical, and morphological properties of respirators layers after sterilization.

Separation of Composites for Recycling: Measurement of Electrostatic Charge of Carbon and Glass Fiber Particles

Separation of Composites for Recycling: Measurement of Electrostatic Charge of Carbon and Glass Fiber Particles

Electroosmosis as a probe for electrostatic correlations.

We study the role of ionic correlations on the electroosmotic flow in planar double-slit channels, without salt. We propose an analytical theory, based on recent advances in the understanding of correlated systems. We compare the theory with mean-field results and validate it by means of dissipative particle dynamics simulations. Interestingly, for some surface separations, correlated systems exhibit a larger flow than predicted by mean-field. We conclude that the electroosmotic properties of a charged system can be used, in general, to infer and weight the importance of electrostatic correlations therein.

Effect of Cutting Parameters on Tribo-Electric Charging in the Ultra-High Precision Diamond Turning of an RGP Contact Lens Polymer

This study present measurements of electrostatic charge that were performed in order to obtain the factors that influence the charging behaviour in the diamond turning process of advanced contact lens polymers. This can be used to decrease tool wear provided that tribo-electric tool wear is dominant in cutting contact lens polymers.The effective medical application of contact lenses is heavily dependent on their form accuracy and surface integrity. Tribo-electric charge which occurs when cutting polymeric contact lenses play a key role, having direct influence on the targeted form accuracy and surface quality of contact lenses. The research goal is to find out what parameter determine the amount of tribo-electric tool wear. The analysis of variance (ANOVA) was used to establish the statistical significance of the cutting parameters on Tribo-electric charge. The results revealed that depth of cut of cut strongly affects the Tribo-electric charge followed by cutting speed, feed rate and interaction between depth and speed.

Investigation of Electrostatic Behavior of Dry Powder-Inhaled Model Formulations

The accumulation of electrostatic charge on drug particles and excipient powders arising from interparticulate collisions or contacts with other surfaces can lead to agglomeration and adhesion problems during the manufacturing process, filling, and delivery of dry powder inhaler (DPI) formulations. The objective of the study was to investigate the role of triboelectrification to better understand the influence of electrostatic charge on the performance of DPIs with 2 capsule-based dimensionally similar devices constructed with different materials. In addition, strategies to reduce electrostatic charge build up during the manufacturing process, and the processes involved in this phenomenon were investigated. Electrostatic charge measurements showed that there was a significant difference in electrostatic charge generated between tested formulations and devices. This affects particle detachment from carrier and thus significantly impacts aerosol performance. Conditioning fluticasone DPI capsules at defined temperature and humidity conditions reduced electrostatic charges acquired during manufacturing. Conditioning salmeterol DPI capsules at same conditions seemed disadvantageous for their aerosol performance because of increasing capillary forces and solid bridge formation caused by water absorption. Knowledge and understanding of the role of electrostatic forces in influencing DPI formulation performance was increased by these studies.

Wpływ metody pomiaru na wielkość ładunków elektrostatycznych w czasie szlifowania drewna sosnowego

In the paper is presented a station to measurement of electrostatic charge generated during grinding operation of pinewood. Size of the charge was determined in course of measurement of voltage in function of time. It has been investigated an effect of two types of abrasive papers: general-purpose paper of PS 18E brand and antistatic one of PS 15F brand on value of the voltage during grinding operation, and weight efficiency of a specimens made from the pinewood, at constant pressure equal to p = 4,54 kPa and variable grinding speed vc in range from 12,1 to 24,2 m/s. It was found that the method of measuring electrostatic charges by recording voltage in the time function U = f(t) has a significant effect primarily on the sign of arising charges and the repeatability of the obtained voltage waveforms during grinding.

Simultaneous measurement of electrostatic charge and its effect on particle motions by electrostatic sensors array in gas-solid fluidized beds

Repeated particle-particle and particle-wall collisions and frictions lead to the generation and accumulation of electrostatic charges in the gas-solid fluidized beds. Variations of electrostatic signals are a rich source of information on particle motions and charging, which have rarely been explored and interpreted. To gain a more comprehensive understanding of the induced electrostatic signals in the fluidized beds, an array of arc-shaped induced electrostatic sensors were attached to the outer wall of a fluidized bed. Combined with cross-correlation method, induced electrostatic voltage signals and correlation velocity of particles were measured simultaneously. It was found that electrostatic charges accumulation restrained the particle motions while the average correlation velocity of particles increased with the amount of injecting liquid antistatic agent. Based on the analyses of induced electrostatic signals, the particle correlation velocity, and the particles charge-to-mass ratio under different charging levels, a predictive model of the average particles charge-to-mass ratio was established. Compared with the results obtained from Faraday cup, the estimated results showed a relative error no more than 40%. Simultaneous measurement of particle correlation velocity and particles charge-to-mass ratio were complemented by arc-shaped induced electrostatic sensors array combined with cross-correlation method.

Implementation of Faraday cup electrostatic charge measurement technique in high-pressure gas–solid fluidized beds at pilot-scale

Elevation of operating pressure in gas–solid fluidized beds affects the bed hydrodynamics, which in turn could affect the extent of bed electrification and reactor wall coating due to electrostatic charge generation. In this work, a pilot plant high-pressure gas–solid fluidization system housing the Faraday cup electrostatic charge measurement technique is introduced in order to study the underlying mechanism of electrostatic charge generation causing fluidized bed wall fouling at pressures up to 25barg. A previously developed on-line electrostatic charge measurement technique containing two Faraday cups was successfully implemented in the high-pressure system. The effect of operating pressure on gas–solid fluidized bed electrification was examined under operating pressures of 0 and 25bar (gauge) by fluidizing polyethylene resin directly received from a commercial reactor. Experimental results showed that the magnitude of reactor wall coating increased with the increase of operating pressure. The wall coating contained positively as well as negatively charged particles indicating the occurrence of bipolar charging within the fluidized bed. Finally, based on the experimental results obtained in this work the mechanism of fluidized bed column wall coating formation was discussed.

Electrostatic Charge Measurements of Droplets of Various Liquids Falling over a Large Distance

AbstractIn order to contribute to a better understanding of the electrostatic phenomena appearing during splash filling of liquids and to clarify the reasons why this process is suspected to increase static electrification especially due to atomization, accurate experiments of charge measurements were made on droplets of various liquids falling over a large distance (5 m). Eleven liquids of different conductivity and surface tension were tested. The results confirm that no charge evolution appears even over a long falling distance. A possible explanation of the static charge increase in splash filling is presented.

Impact of Addition of a Catalyst or Its Support on Reactor Wall Coating Due to Electrostatic Charging during Fluidization of Polyethylene

In this work the degree of fluidized bed electrification and reactor wall coating were investigated where a metallocene catalyst and its silica support were added to a bed of polyethylene resin and fluidized in a carbon steel reactor, 0.1 m in diameter and operating under ambient conditions. Tests were conducted to simulate industrial polyethylene reactors where both polyethylene and catalyst particles are present during the fluidization process. Since majority of the catalyst surface area is occupied by its support, the influence of the support was also examined. The electrostatic charge measurement technique used was similar to that described by Sowinski et al.1 Results demonstrated that both the catalyst and the silica support augmented the fluidized bed reactor wall coating due to their inherent large specific charge, which was partly gained during their passage through the injection tube. This finding demonstrates the possibility that in commercial gas-phase polyethylene fluidized bed reactors the ca...

Semicircular Lipoatrophy: An Electrostatic Hypothesis

Background: Semicircular lipoatrophy (SL) is a benign pathology characterized by subcutaneous adipose tissue atrophy. Objective: To determine causes of SL. Methods: We performed research on 42 cases of SL who had developed symptoms of lipoatrophy with a technical study of the building and clinical study of the affected patients. Results: Electromagnetic field and electrostatic charge measurements were performed. No signals different from typical radio, TV and other wireless communication devices were recorded. Electrostatic charges were recorded in floors, environments and on different furniture; they were positive, and all charges disappeared on contact with the worker's skin. Data about the workplace were collected, and clinical examinations were performed, including blood and biochemistry tests and 18 ultrasound skin tests. Conclusions: As no abnormal electromagnetic measurements were found and electrostatic changes and occupational behaviors showed some relevant data and as after changes in order to control the electrostatic environment all of them improved, we can conclude that electrostatic charges but not electromagnetic ones are the main cause of SL.

Influence of process parameters on content uniformity of a low dose active pharmaceutical ingredient in a tablet formulation according to GMP.

The article describes the development and production of tablets using direct compression of powder mixtures. The aim was to describe the impact of filler particle size and the time of lubricant addition during mixing on content uniformity according to the Good Manufacturing Practice (GMP) process validation requirements. Processes are regulated by complex directives, forcing the producers to validate, using sophisticated methods, the content uniformity of intermediates as well as final products. Cutting down of production time and material, shortening of analyses, and fast and reliable statistic evaluation of results can reduce the final price without affecting product quality. The manufacturing process of directly compressed tablets containing the low dose active pharmaceutical ingredient (API) warfarin, with content uniformity passing validation criteria, is used as a model example. Statistic methods have proved that the manufacturing process is reproducible. Methods suitable for elucidation of various properties of the final blend, e.g., measurement of electrostatic charge by Faraday pail and evaluation of mutual influences of researched variables by partial least square (PLS) regression, were used. Using these methods, it was proved that the filler with higher particle size increased the content uniformity of both blends and the ensuing tablets. Addition of the lubricant, magnesium stearate, during the blending process improved the content uniformity of blends containing the filler with larger particles. This seems to be caused by reduced sampling error due to the suppression of electrostatic charge.

MEMS Electrometer With Femtoampere Resolution for Aerosol Particulate Measurements

Electrostatic charge measurements are at the base of chemical, physical and biological experiments. In this paper, we present an electrometer based on the vibrating capacitance of a microelectromechanical systems (MEMS) resonator for the detection of small currents from ionized particles in an aerosol particle detection system. We use a porous sensing-electrode coupled to a MEMS resonating electrometer. Operating at resonance, charge is collected on the MEMS electrometer and modulated at the resonant frequency and its harmonics. Induced voltage is read with a low-leakage very high-input impedance feedback amplifier. Because of the specific readout technique, a switched-reset is used to prevent charge saturation. Sensitivity improvements are achieved by modifying the low noise-readout amplifier by reducing input-referred noise and parasitic capacitance. The electrometer achieves a noise floor <;1 fA produced by 10 nm diameter particles within an airflow of 1.0 L/min. At this flow rate, the minimum detectable current (1 fA) corresponds to a minimum measureable particle density of 400 cm-3. The MEMS electrometer is compared with and calibrated against commercial electrometer and a particle counter, respectively.

Probing pharmaceutical powder blending uniformity with electrostatic charge measurements

Abstract The tribo-electrification of the powder particles is ubiquitous in pharmaceutical powder blending processes. It usually carries a negative connotation as particles may jam and stick inside equipments. Though it is practically important, the tribo-electrification is rarely characterized quantitatively in pharmaceutical areas. The purpose of this research was to examine the relationship between the electrostatic properties of pharmaceutical powders and blend homogeneity. We hypothesized that once the powder mixtures reached the homogeneity, the bulk electrostatic charges of the randomly collected samples at different spatial locations of the powder mixture would converge. Otherwise, the charges would scatter over a wide range due to non-uniformity of the powder mixture. Three prototypic pharmaceutical mixtures with (or without) caffeine as a model active pharmaceutical ingredient, microcrystalline cellulose as a filler/binder (Avicels), Cab-o-sil as a glidant, and Magnesium Stearate as a lubricant, were formulated and mixed in a V-blender. The resulted electrostatic charges were measured with a Faraday Cup connected to an electrometer and a strong correlation between electrostatic charges and blend homogeneity was found. The electrostatic charge monitoring method could be potentially used for assessing the blend uniformity. We also discovered the cyclical blending/deblending phenomena occurred with certain periodicity patterns upon continuous powder blending process, which may help design proper pharmaceutical blending procedures.

Measurement of electrostatic dipoles and net charge on particles suspended in air

Explanations of electrostatic behaviour of individual particulates have always invoked net electrostatic charge and neglected any fixed dipoles arising from nonuniform distribution of charge on their surface. Here for the first time, techniques are described to measure both net charge of each particle and its dipole moment by sampling, photography, and movement analysis of particles suspended in air. In this study, spherical dielectric particles were subjected to a non-uniform electric field (around a probe) and their trajectory was followed with a multi-flash high-speed video camera. These first results support the existence of fixed or “permanent” dipoles, on tribocharged particles.

An electrodynamic sensor for electrostatic charge measurement

Abstract Electrodynamic sensors are used in the process industry because they are low cost and robust. Though frequently used very little fundamental work on them has been reported. This paper describes an investigation into characteristics of hemispherically and rectangularly shaped sensors. Two parameters are investigated, the effect of sensor area on sensitivity and the spatial filtering effect of the sensor due to its finite size. Models are proposed and results obtained using them compared with experimental values.

New technique for electrostatic charge measurement in gas–solid fluidized beds

Electrostatic charge generation within gas–solid fluidized bed reactors has been a concern to industry for many years. Over the years, numerous methods for measuring this phenomenon within a fluidization column have been proposed. This paper focuses on the design of a new method that minimizes effects such as extra charging due to particle handling and bed hydrodynamic disruption due to the location of the measurement device. In addition, the new method provides the bulk charge of the bed particles rather than a local measurement. The device is flexible and can be adapted to a range of fluidization columns. The new method developed consisted of a Faraday cup placed within the windbox of a fluidization column. The distributor plate was designed in such a way that it can be automatically opened to drop the charged fluidizing particles into the Faraday cup below. The new measurement technique was validated by conducting fluidization experiments in a system consisting of a 0.10 m in diameter carbon steel column with glass beads as the fluidizing particles. The technique was proven to be suitable for measuring the total net electrostatic charges in gas–solid fluidized beds.

Design of a Device for Simultaneous Particle Size and Electrostatic Charge Measurement of Inhalation Drugs

To develop a device for simultaneous measurement of particle aerodynamic diameter and electrostatic charge of inhalation aerosols. An integrated system consisting of an add-on charge measurement device and a liquid impinger was developed to simultaneously determine particle aerodynamic diameter and electrostatic charge. The accuracy in charge measurement and fine particle fraction characterization of the new system was evaluated. The integrated system was then applied to analyze the electrostatic charges of a DPI formulation composed of salbutamol sulphate-Inhalac 230 dispersed using a Rotahaler. The charge measurement accuracy was comparable with the Faraday cage method, and incorporation of the charge measurement module had no effect on the performance of the liquid impinger. Salbutamol sulphate carried negative charges while the net charge of Inhalac 230 and un-dispersed salbutamol sulphate was found to be positive after being aerosolized from the inhaler. The instantaneous current signal was strong with small noise to signal ratio, and good reproducibility of charge to mass ratio was obtained for the DPI system investigated. A system for simultaneously measuring particle aerodynamic diameter and aerosol electrostatic charges has been developed, and the system provides a non-intrusive and reliable electrostatic charge characterization method for inhalation dosage forms.

Investigation of Electrostatic Behavior of a Lactose Carrier for Dry Powder Inhalers

This study aims to elucidate the electrostatic behavior of a model lactose carrier used in dry powder inhaler formulations by examining the effects of ambient relative humidity (RH), aerosolization air flow rate, repeated inhaler use, gelatin capsule and tapping on the specific charge (nC/g) of bulk and aerosolized lactose. Static and dynamic electrostatic charge measurements were performed using a Faraday cage connected to an electrometer. Experiments were conducted inside a walk-in environmental chamber at 25 degrees C and RHs of 20% to 80%. Aerosolization was achieved using air flow rates of 30, 45, 60 and 75 L/min. The initial charges of the bulk and capsulated lactose were a magnitude lower than the charges of tapped or aerosolized lactose. Dynamic charge increased linearly with aerosolization air flow rate and RH. Greater frictional forces at higher air flow rate induced higher electrostatic charges. Increased RH enhanced charge generation. Repeated inhaler use significantly influenced electrostatic charge due to repeated usage. This study demonstrated the significance of interacting influences by variables commonly encountered in the use DPI such as variation in patient's inspiratory flow rate, ambient RH and repeated inhaler use on the electrostatic behavior of a lactose DPI carrier.

Chargeability measurements of selected pharmaceutical dry powders to assess their electrostatic charge control capabilities

The purpose of this study was to develop an instrument (the Purdue instrument) and the corresponding methodologies to measure the electrostatic charge development (chargeability) of dry powders when they are in dynamic contact with stainless steel surfaces. The system used an inductive noncontact sensor located inside an aluminum Faraday cage and was optimized to measure the charging capabilities of a fixed volume of powder (0.5 cc). The chargeability of 5,5-diphenyl-hydantoin, calcium sulfate dihydrate, cimetidine, 3 grades of colloidal silicon dioxide, magnesium stearate, 4 grades of microcrystalline cellulose, salicylic acid, sodium carbonate, sodium salicylate, spray-dried lactose, and sulfinpyrazone were tested at 4 linear velocities, and the particle size distribution effect was assessed for 3 different grades of colloidal silicon dioxide and 4 different grades of microcrystalline cellulose. The chargeability values exhibited a linear relationship for the range of velocities studied, with colloidal silicon dioxide exhibiting the maximum negative chargeability and with spray-dried lactose being the only compound to exhibit positive chargeability. The instrument sensitivity was improved by a factor of 2 over the first generation version, and the electrostatic charge measurements were reproducible with relative standard deviations ranging from nondetectable to 33.7% (minimum of 3 replicates). These results demonstrate the feasibility of using the Purdue instrument to measure the electrostatic charge control capabilities of pharmaceutical dry powders with a reasonable level of precision.