Electrical Impedance Technique Research Articles

Hydrodynamic Study of a Hybrid Electro-Flotation Column

Bubble columns are used in the mining industry for mineral recovery but are also widely utilized in the chemical and petrochemical industry. The hydrodynamic characteristics of their performance is a field of interest with a number of points, which are nonetheless poorly understood, and a considerable amount of methods have aimed to shed light on the flow regimes that prevail in the columns. The study of the hydrodynamic part of a flotation process should consider characteristics such as air flow, volumetric gas fraction, flow field, and bubble size, along with the mechanical and design factors and pulp properties. The present work aims to elucidate the characteristics of the gas phase of a hybrid flotation system. For this purpose, a hybrid flotation column was designed and constructed and the bubbles size distributions at different radial positions in the flotation column were computed by analyzing high resolution digital images. A patented electrical impedance technique was employed to instantaneously measure the local volumetric gas fraction. Flow dispersion in the column was studied by residence time distributions using conductivity tracers. The experimental results are discussed to comprehend the variation in the gas fraction in the column. In particular, the study showed that the size of the bubbles changed from the center to the walls of the column, and this was observed both radically and vertically. Moreover, the size of the bubbles affected the volume fractions, and no coalescence of the bubbles was observed. Finally, the dispersion of the tracer in the working solution was distributed uniformly in the volume of the column, with a time difference for the four positions of the column.

Validation of Electrical Impedance Technique in Real-Time Using the xCELLigence as an Interference-Free Method for Assessing Cytotoxicity of Silver and Hydroxyapatite Nanoparticles

This study demonstrated the utility of real-time electrical impedance, utilizing the xCELLigence system to assess the cytotoxic effects of silver nanoparticles (AgNPs) and hydroxyapatite nanoparticles (HANPs) on A549 cells. Method validation confirmed the accuracy and reliability of cell index (CI) measurements. The NPs were thoroughly characterized to confirm their elemental composition, size, and morphology through energy dispersive spectroscopy, transmission electron microscopy, and dynamic light scattering. Cytotoxicity assays revealed a concentration-dependent response. Exposure to AgNPs resulted in a significant change in CI, with a pronounced increase followed by a sharp decrease in the first few hours after treatment at the highest concentration of 50 μg mL–1. This pattern suggested an initial cell response to AgNPs exposure, possibly indicating mechanisms such as apoptosis or necrosis, followed by a decrease in cell adhesion. Conversely, HANPs demonstrated a tendency to restore CI at higher concentrations (1-100 μg mL–1) before 48 h, suggesting a potential recovery in cell proliferation capacity. This underscores the diverse cell responses to NPs, emphasizing the sensitivity of the method in detecting subtle cytotoxic effects. These findings highlight the efficacy of real-time electrical impedance in dynamic nanoparticle cytotoxicity assessments, surpassing traditional assays. Adapting to high-throughput screening enhances nanomaterial safety evaluations.

Patterns of Neonatal Thrombocytopenia with A Note on Platelet Indices and Optical Technology – A Cross-Sectional Study

Introduction: Neonatal thrombocytopenia is defined as a platelet count <150×10^9/L regardless of gestational-age. It results from hypo-proliferation in marrow or peripheral destruction of platelets. Platelet count can be rapidly measured using automated hematology analyzers, but peripheral smear remains best method. The causes of neonatal thrombocytopenia are defined by time of presentation into foetal (mainly TORCH infections), early (< 3 days), and late. The present study highlights pattern and severity of neonatal thrombocytopenia in study hospital, adding importance of platelet indices and optical technology.
 Aim: To study patterns and severity of neonatal thrombocytopenia, platelet indices and to measure accuracy of platelet count by optical technology methods against peripheral smear.
 Materials and methods: A cross-sectional study done for a period of 8 months from December 2018 to July 2019, at ASRAM medical college, Eluru. During this period blood samples of 113 critical cases of newborns, admitted with thrombocytopenia, were collected in Ethylenediamine tetra acetic acid (EDTA) vials. The platelet count was analyzed by two automated analyzers, Sysmex XN1000 and Horiba ABX Pentra XL 80. The Leishman-stained films were examined under a light microscope. ANOVA test was used to find mean difference between platelet counts, sensitivity, and specificity, and accuracy was calculated by MEDCALC CALCULATOR.
 Results: Out of total of 113 critical cases of new-borns admitted to Neonatal intensive care unit (NICU) at institute, 85 presented with thrombocytopenia. The variation of platelet indices was noted in 40 cases, blood cultures were collected in 77 cases. Thrombocytopenia showing platelet count less than 20,000/ mm3 is considered very severe, with 30.5% (26 cases) of total number. Elevated platelet indices were noted at 47.5%. The common clinical diagnosis was neonatal sepsis (42.3%), followed by neonatal jaundice (18.8%). The light scatterer principle of platelet evaluation proved to have better accuracy than electrical impedance, in comparison to peripheral smear findings.
 Conclusion: The study concludes that neonatal septicemia is major cause of neonatal thrombocytopenia as proved by correlating platelet count with platelet indices. And also, usage of automated hemogram reports with platelet indices, is a source of information to suspect etiology of thrombocytopenia thereby preventing adverse outcomes. The principle of Optical Light scatterer technique in an automated analyzer gives better results than the electrical impedance technique for detecting platelet count value, though peripheral smear examination is mandatory for confirmation.

Development of piezoelectric-based technology for application in civil structural health monitoring

Piezoelectric material, as one of the great potential materials, had attracted lots of attention all over the world due to its distinguish advantages. In this paper, the development of piezoelectric-based technology for application in the field of civil structural health monitoring (CSHM), was summarized and discussed. Based on the different identification mechanisms, the piezoelectric transducer-based technology can be divided into two main approaches as the active or passive sensing and detection methods. This paper summarized the development of these two approaches and discussed their applications in the area of civil structural health monitoring, such as structural and concrete engineering, bridge engineering, pipeline engineering, protection engineering for geological hazards and earthquake disasters, and so on. In addition, the electrical mechanical impedance (EMI) technique, as one of the active identification methods, was also detailly presented. Finally, its great potential for the piezoelectric-based technique was presented based on the detail discussion, especially in the areas of civil structural health monitoring.

Electrical and mechanical analysis to evaluate the cultivar difference in strawberries with respect to their bruising sensitivities and mass loss acceleration

This study investigated the differences in the bruising characteristics of three strawberry cultivars that were subjected to mechanical compression, while elucidating the effect of bruising on the acceleration of mass loss during storage; these investigations were aimed at achieving long-term transportation. The length of the coordinate at the top of the circular arc of Cole-Cole plots from the origin (LTO) was obtained using electrical impedance techniques and was employed as an indicator of the degree of bruising. The LTO values of the control samples were approximately 30,000 Ω; however, they decreased with the increasing compression strain, so the strain was evaluated to be the primary factor for their bruising. Further, a disparity was observed in different cultivars with regard to their fragilities to compression. Mass loss of samples during storage was approximately 0.01 – 0.03 (-); however, owing to an increase in the degree of bruising, the mass loss for each cultivar was accelerated during storage; moreover, there are significant differences among the cultivars. These findings demonstrate that selecting an appropriate cultivar alleviates bruising and deterioration during transportation. Moreover, the combination analysis using electrical analysis and measurement of quality decline rate may be advantageous for the selection of good cultivars.

Development in Tear Film Osmolarity Assessments: A Review.

The aim of this article is to review the development in the assessment of tear film with tear osmolarity techniques. Also, to find out the average score for tear osmolarity in normal and keratoconjunctivitis sicca (KCS) patients based on the published work. The use of tear osmolarity techniques has been started about 50 years ago. Over the last years a number of researchers have investigated the human tear osmolarity. The tear osmolarity assessment techniques have two procedures. The first procedure which is old, that involves the detection of freezing point depression and vapour pressure. The second one which is more advance and known as the electronic method, that involves the use of electrical impedance technique. All techniques used to assess tear osmolarity are good, accurate, reliable and provide comparable data. Based on the published work reviewed in this article, the average tear osmolarity for normal subjects is 303.2 ± 7.0 compared to 322.7 ± 15.9 in subjects with KCS.

Skin hydration dynamics investigated by electrical impedance techniques in vivo and in vitro

Skin is easily accessible for transdermal drug delivery and also attractive for biomarker sampling. These applications are strongly influenced by hydration where elevated hydration generally leads to increased skin permeability. Thus, favorable transdermal delivery and extraction conditions can be easily obtained by exploiting elevated skin hydration. Here, we provide a detailed in vivo and in vitro investigation of the skin hydration dynamics using three techniques based on electrical impedance spectroscopy. Good correlation between in vivo and in vitro results is demonstrated, which implies that simple but realistic in vitro models can be used for further studies related to skin hydration (e.g., cosmetic testing). Importantly, the results show that hydration proceeds in two stages. Firstly, hydration between 5 and 10 min results in a drastic skin impedance change, which is interpreted as filling of superficial voids in skin with conducting electrolyte solution. Secondly, a subtle impedance change is observed over time, which is interpreted as leveling of the water gradient across skin leading to structural relaxation/changes of the macromolecular skin barrier components. With respect to transdermal drug delivery and extraction of biomarkers; 1 h of hydration is suggested to result in beneficial and stable conditions in terms of high skin permeability and extraction efficiency.

Use of noninvasive imaging in the management of skin cancer.

To evaluate noninvasive imaging techniques in the management of skin cancers. In the last decades, a wide range of noninvasive imaging methods has been developed in the field of dermatooncology with the aim to detect and assess the several structural and molecular changes that characterize skin cancer development and progression. In this review, we discuss the current and emerging applications of noninvasive imaging approaches in skin cancer management, such as digital photography, dermoscopy, ultrasound sonography, reflectance confocal microscopy, optical coherence tomography, electrical impedance techniques, Raman spectroscopy, multispectral imaging, fluorescence imaging, and multispectral optoacustic tomography.

A new six-electrode electrical impedance technique for probing deep organs in the human body.

Electrical impedance measurements of biological tissue have many potential applications and tetrapolar impedance measurement (TPIM) with four electrodes is traditionally used which eliminates high skin contact impedance. A linear array of four electrodes for TPIM on the horizontal plane of a cylindrical volume conductor of diameter D, where the length of the array is πD/2 with potential electrodes near the centre of the array, will give a high sensitivity near the surface which reduces rapidly with depth. A recently proposed six-electrode variation of TPIM uses an additional pair of potential electrodes on the opposite side of the volume conductor in the same horizontal plane around the circumference, with the expectation that the sensitivity of the deeper regions will thereby be enhanced. The present work carries out a finite element simulation (using COMSOL) and an experimental phantom study (saline phantom) to quantitatively evaluate the improvement obtained by this new method. The new configuration doubled the sensitivity at the central region, which was reasonably uniform over a wider zone, gradually increasing towards the potential electrodes on both sides. This would be useful for a range of biological studies of deep body organs such as lungs, stomach, and bladder. where the respective external body shapes may be approximated by an oval cylinder and where electrical impedance techniques have shown promise.

Influence of Newtonian and non-Newtonian fluid behaviour on void fraction and bubble size for a gas-liquid flow of sub-millimeter bubbles at low void fractions

This study compares the effect of Newtonian and non-Newtonian blood-mimicking test liquids on void fraction and bubble size distribution (BSD) for the case of gas–liquid bubbly flow. Along with this comparison, the novelty of the present work is extended to the examined conditions, which combine low void fractions (<10−1) with bubbles smaller than 1 mm, resembling bubbly flow in human bloodstream during Decompression Sickness. Such conditions, however, can be also found in common two-phase applications such as subcooled flow boiling in macro-channels. Experiments are performed in co-current upward bubbly flow. Void fraction and BSD are determined by a non-intrusive electrical impedance technique and by image analysis of bubbly flow images, respectively. Xanthan gum is employed (0, 150 and 1000 ppm) to impart non-Newtonian (shear-thinning) behaviour to the baseline aqueous glycerol/NaCl test liquid. The role of surface tension (by adding Triton X-100) and gas/liquid superficial velocities (Usg, Usl) on acquired data is studied as well. Results demonstrate that increase of bubble size and decrease of void fraction is primarily due to the non-Newtonian liquid character rather than the increase of dynamic viscosity caused by the addition of high Xanthan gum concentration. The addition of surfactant (Triton X-100) decreases bubble size and increases void fraction. Furthermore, bubble size and void fraction increase with Usg and decrease with Usl. Void fraction signal fluctuations show a strong dependence on bubble size. Furthermore, the performance of an empirical equation that predicts average bubble diameter from void fraction statistical quantities is tested and seems to be unaffected by the Newtonian/non-Newtonian liquid behaviour. Of particular interest are the intense peaks noticed in void fraction signals for the highest examined Xanthan gum concentration (1000 ppm) and the lowest examined liquid superficial velocity (2.89 cm/s). These peaks correspond to voluminous bubbles clusters rising among isolated bubbles, which do not appear at higher liquid velocities.

Analysis of measurement electrode location in bladder urine monitoring using electrical impedance

PurposeThe aim of this study was to document more appropriate electrode location of a four-electrode-based electrical impedance technology in the monitoring of bladder filling, and to characterize the relationship between bladder filling duration and the measured electrical impedances.MethodsA simulation study, based on a 2-dimension computational model, was conducted to determine the preferable locations of excitation and measurement electrodes in a conventional four-electrode setup. A human observation study was subsequently performed on eight healthy volunteers during natural bladder urine accumulation to validate the result of the simulation study. The correlation between the bladder filling time and the measured electrical impedance values was evaluated.ResultsThe preferable location of measurement electrodes was successively validated by the model simulation study and human observation study. Result obtained via the selected electrodes location revealed a significant negative correlation (R = 0.916 ± 0.059, P < 0.001) between the measured electrical impedance and the urine accumulation time, which was consistent with the result of simulation study.ConclusionsThe findings in this study not only documented the desirable electrodes location to monitor the process of bladder urine accumulation using four-electrode measurement, but also validated the feasibility of utilizing electrical impedance technique to monitor and estimate the bladder urine volume for those with urological disorders.

Synthesis and characterization of V2O5/PANI thin films for application in amperometric ammonia gas sensors

Abstract Studies of xerogel vanadium pentoxide hybrids in the presence of polyaniline (V2O5/PANI) for ammonia gas detection are presented. The hybrid materials were obtained in an oxidative polymerization/intercalation process, in which gel reacted with the monomers of the polymers. In situ characterization revealed V2O5/PANI hybrids with lamellar structure. Finally, the electric impedance technique was used for determining the optimal frequency band for operation of an Ag/V2O5/PANI/Ag amperometric ammonia gas sensor, to achieve linearity and stability. The results indicate that the sensor can detect gaseous ammonia in the 0–54 ppm range of concentrations. This characteristic is important for successful applications in easy to handle and low-cost ammonia gas sensors for animal confinement husbandry, for which current variation and difficulties related to electrode effects and dielectric absorption of V2O5 and PANI are negligible.

T136. Assessing myofiber size without biopsy: A novel application of electrical impedance techniques

Introduction In electrical impedance myography (EIM) a weak electrical current is applied to a muscle and the resulting voltages measured. These voltages can provide structural and compositional information on the tissue, including the presence of myofiber loss and the deposition of fat and connective tissue. In addition, based on standard bioimpedance theory, by applying a multifrequency current, structural characteristics of the fibers can be identified, including myofiber size. In this study, we assessed the potential of EIM to identify myofiber size non-invasively in both healthy and diseased muscle. Methods In electrical impedance myography (EIM) a weak electrical current is applied to a muscle and the resulting voltages measured. These voltages can provide structural and compositional information on the tissue, including the presence of myofiber loss and the deposition of fat and connective tissue. In addition, based on standard bioimpedance theory, by applying a multifrequency current, structural characteristics of the fibers can be identified, including myofiber size. In this study, we assessed the potential of EIM to identify myofiber size non-invasively in both healthy and diseased muscle. Results Using the LASSO approach, we successfully predicted myofiber size with high accuracy in the wild type immature (root mean standard error (RMSE) in the range of ±69.05 (16.2% with respect to the average myofiber size of 491 μ m 2 ). Similar accuracy was also achieved in the ALS animals with an RSME of only 14% in mean myofiber area (corresponding to ±207 μ m 2 for a mean area of 1488 μ m 2 ); in addition, in this group of animals we were also able to demonstrate that we could accurately predict the coefficient of variation in fiber size with a RMSE of only 8.8%. Conclusion These results demonstrate that impedance techniques can be used to assess myofiber size without the need for actual tissue biopsy. This approach for assessing the degree of myofiber size demands further development and potential application in a variety of future contexts including the assessment of neuromuscular disease status, disuse-related alterations, and the impact of therapy.

Silk fibroin as a platform for dual sensing of vitamin B12 using photoluminescence and electrical techniques

The amalgamation of natural origin materials and technologies for label-free and real time detection is pertinent in analytical field. In this study, Bombyx mori silk fibroin protein (BMSF) has been utilized for the dual sensing of vitamin B12 via fluorescence and electrical impedance techniques. The processing of BMSF is done to generate an aqueous solution of BMSF along with the development of micro patterned thin films via soft lithography technique. The BMSF aqueous solution exhibit auto fluorescence property and thereby utilized for label free detection of vitamin B12 with an estimated limit of detection (LOD) of about 0.003 × 10−6 g/uL. This is followed by impedimetric detection of vitamin B12 using the micro patterned BMSF thin films. A LOD of 17.8 ppm and 0.25 ppm are achieved in aqueous solution and human blood serum, respectively. Taken together, this work demonstrates a potential label free dual sensing mode for sensitive detection of micronutrient vitamin B12.

Degassing of a pressurized liquid saturated with dissolved gas when injected to a low pressure liquid pool

Bubbles forming due to decompression of a liquid saturated with dissolved gas at elevated pressures when it enters a low pressure liquid pool can either limit or promote the efficiency of several ground and space applications. Among the experimental parameters influencing flow decompression degassing, dissolution pressure is the most studied, yet controversial, parameter. The present work aims to shed light on how dissolution pressure of a liquid affects the final size of bubbles and the generated gas fraction by conducting gas desorption (degassing) experiments of liquid jets that decompress passing though a nozzle to a vertical column filled with the same non-degassed liquid. Bubbles size distributions at different radial positions in the column are computed analyzing high resolution digital images. A patented electrical impedance technique is employed to measure instantaneously local volumetric gas fraction. Flow dispersion in the column is studied by residence time distributions using conductivity tracers. On-line continuous dissolved oxygen measurements yield the kinetics and final extent of degassing. Experimental results are discussed to comprehend why bubbles size distributions vary with dissolution pressures and how this variation affects gas fraction in the column.

Design and development of microcontroller based instrumentation for studying complex bioelectrical impedance of fruits using electrical impedance spectroscopy

AbstractElectrical impedance spectroscopy (EIS) is an electrical impedance technique to characterize the fruits and vegetables in terms of their frequency dependent bioimpedance profile. Standalone, portable, and low‐cost instrumentation is always preferred for conducting EIS procedures. This article reports the studies on the design and development of a Microcontroller based portable impedance measurement system to conduct the EIS studies on the fruits during ripening and storage. The proposed laboratory based EIS system is developed with a Microcontroller ATmega16, a Direct Digital Synthesizers based constant current source AD5930, a current to voltage converter, a low pass filter, and a DSO. To test and evaluate the developed system, the cucumber impedance is studied under the storage condition using EIS to characterize the cucumber freshness from the electrical impedance data. The real parts, imaginary parts of the cucumber impedance are calculated and the Nyquist diagrams are analyzed to study the equivalent circuit analysis. The developed system is compared with a standard impedance analyzer and it is observed that the results obtained from the developed system closely match with the data measured by the commercial impedance analyzer. The developed system is also found suitable for EIS studies of fruits, vegetables, and other biological tissues. The developed system is found low‐cost, fast, and user friendly. PCB based version of the proposed system with display unit will be found as a portable, standalone, and EIS system suitable for outdoor measurement in agricultural‐field applications.Practical applicationsMicrocontroller based low cost electrical impedance spectroscopy (EIS) has been developed and is studied for EIS based fruit ripening analysis. The system is compared with the standard commercial impedance analyzer and it is found suitable fruit ripening characterization, vegetable freshness detection, and health studies of other biological tissues. The microcontroller based EIS system is found portable, low cost, fast, and user friendly device which can be used in laboratory, cultivation fields, cold storages and shops and markets. The developed system allows nontechnical person to operated and collect the data from fruit and vegetable samples. The system acquired data significantly correlate the bioimpedance variation with the ripening states which can be potentially utilized to study the fruit ripening noninvasively at low cost. Hence the product‐form of the developed devise could even be operated by field persons, farmers, and other common men to evaluate the fruit ripening and vegetable freshness.

Detection and quantification of Alicyclobacillus acidoterrestris by electrical impedance in apple juice

Alicyclobacillus acidoterrestris is a thermotolerant bacterium able to grow in fruit juices and drinks, as the spoilage by Alicyclobacillus in the final product does not product any gas, but leads to a “medicine flavor” due to the formation of guaicol. Also, its detection is a challenge for the quality control departments, because it takes several days to get the results of traditional microbiology methods. This study aimed at developing a more accurate electrical impedance technique for the detection of A. acidoterrestris in concentrated apple juice. Samples of apple juice were inoculated with A. acidoterrestris spores isolated from a peach and grape juice. For the spore germination, several heat-shock treatments were tested (80 °C/10 min, 70 °C/20 min and 60 °C/30 min). Direct and indirect electrical impedance was applied to detect and quantify the microorganism in the inoculated apple juice, using BAT broth and Bimedia 002A (pH 4). The 80 °C/10 min treatment was selected for spore activation. The valid electrical impedance technique was the indirect method in BAT broth, which measured the changes in the impedance through the formation of CO2. In addition, a positive correlation (r = 0.98, R2 = 0.97) was observed between the classical microbiology (BAM agar) and the indirect impedance method.

Spectroscopic Methods to Investigate Liquid–Porous Material Interactions: An Overview of Optical and Electrical Impedance Techniques

An overview of spectroscopic methods to investigate physical processes specific to the water-based ink/substrate interaction is made in this work. Optical techniques (as VIS reflectometry, IR-ATR and spectroellipsometry) and electrical impedance spectroscopy have been employed to study physical phenomena that describe the interaction between water-based mixtures and the substrate for printing; the latter can be absorbent (porous) or non-absorbent of liquid. Therefore, evaporation of aqueous mixtures and/or liquid penetration in porous paper are the main subjects of these studies. After brief introduction in each method, examples of various particular cases are presented and analyzed: evaporation of pure liquids and mixtures, water penetration into paper of various thicknesses, the penetration of different liquids into plain paper. The method of spectroellipsometry was used to characterize the coating of the coated paper for printing industry.

An orbital shear platform for real-time, in vitro endothelium characterization.

Electrical impedance techniques have been used to characterize endothelium morphology, permeability, and motility in vitro. However, these impedance platforms have been limited to either static endothelium studies and/or induced laminar fluid flow at a constant, single shear stress value. In this work, we present a microfabricated impedance sensor for real-time, in vitro characterization of human umbilical vein endothelial cells (HUVECs) undergoing oscillatory hydrodynamic shear. Oscillatory shear was applied with an orbital shaker and the electrical impedance was measured by a microfabricated impedance chip with discrete electrodes positioned at radial locations of 0, 2.5, 5.0, 7.5, 10.0, and 12.5 mm from the center of the chip. Depending on their radial position within the circular orbital platform, HUVECs were exposed to shear values ranging between 0.6 and 6.71 dyne/cm(2) (according to numerical simulations) for 22 h. Impedance spectra were fit to an equivalent circuit model and the trans-endothelial resistance and monolayer's capacitance were extracted. Results demonstrated that, compared to measurements acquired before the onset of shear, cells at the center of the platform that experienced low steady shear stress (∼2.2 dyne/cm(2) ) had an average change in trans-endothelial resistance of 6.99 ± 4.06% and 1.78 ± 2.40% change in cell capacitance after 22 hours of shear exposure; cells near the periphery of the well (r = 12.5 mm) experienced transient shears (2.5-6.7 dyne/cm(2) ) and exhibited a greater change in trans-endothelial resistance (24.2 ± 10.8%) and cell capacitance (4.57 ± 5.39%). This study, demonstrates that the orbital shear platform provides a simple system that can capture and quantify the real-time cellular morphology as a result of induced shear stress. The orbital shear platform presented in this work, compared to traditional laminar platforms, subjects cells to more physiologically relevant oscillatory shear as well as exposes the sample to several shear values simultaneously. Biotechnol. Bioeng. 2016;113: 1336-1344. © 2015 Wiley Periodicals, Inc.

Effect of bubble size on void fraction fluctuations in dispersed bubble flows

It is known that bubble size affects seriously the average void fraction in bubbly flows where buoyant velocities vary considerably with bubble size. On the contrary, there is no systematic literature report about bubble size effects on the intensity and frequency of void fraction fluctuations around the average void fraction. This work aims to provide such information. An electrical impedance technique is employed along with non-intrusive ring electrodes to register void fraction fluctuations down to 10−5. Bubble size fluctuations are estimated from high resolution optical images. Experiments are conducted in co-current upward dispersed bubble flow inside a 21mm tube with average bubble size between ∼50 and ∼700μm. Water and blood simulant are used as test liquids with velocity from ∼3 to ∼30cms−1. The above resemble conditions of Decompression Sickness (DCS) in the bloodstream of human vena cava. It is found that the intensity and frequency of void fraction fluctuations vary appreciably with bubble size at constant gas and liquid flow rates. Moreover, these variations are not random but scale with bubble size. As a first step to quantify this effect, an empirical expression is derived that relates average bubble size to the ratio standard deviation/average value of void fraction.