Viscosity Measurement Techniques Research Articles

Simultaneous Protein Adsorption and Viscosity Measurement using Micropillar-Enhanced Acoustic Wave (μPAW) Device for Pharmaceutical Applications

At the early stages of drug development, the amount of drug materials is rather limited. In this case, viscosity measurement is often postponed to the later stages, where grams of proteins can be produced. Therefore, it is necessary to develop a viscometer capable of measuring the viscosity with high accuracy while requiring low sample volume. This study presents a novel viscosity measurement technique based on measuring the resonance frequency and motional resistance of a micropillar-enhanced acoustic wave (μPAW) device. The μPAW was developed by fabricating micropillars on the quartz crystal microbalance substrate in order to achieve ultra-high sensitivity, thanks to a unique coupling between the micropillar and the resonator. The experimental measurements demonstrated a nonlinear relationship between the density and viscosity of the fluid and the response of μPAW. A calibration correlation was developed using the response of μPAW in aqueous glycerol and sucrose solutions. The measurements were then extended using high-concentration BSA solutions as the model of protein solution. The main advantage of the μPAW device in this work over other viscometers is the ability to simultaneously measure solution viscosity and protein adsorption on the surface. This is a huge step forward in the development of sensing systems for the pharmaceutical industry, where real-time sensing of target biological proteins and measuring the viscosity of a solution is required.

A bio-fabricated tesla valves and ultrasound waves-powered blood plasma viscometer.

Introduction: There is clinical evidence that the fresh blood viscosity is an important indicator in the development of vascular disorder and coagulation. However, existing clinical viscosity measurement techniques lack the ability to measure blood viscosity and replicate the in-vivo hemodynamics simultaneously. Methods: Here, we fabricate a novel digital device, called Tesla valves and ultrasound waves-powered blood plasma viscometer (TUBPV) which shows capacities in both viscosity measurement and coagulation monitoring. Results: Based on the Hagen-Poiseuille equation, viscosity analysis can be faithfully performed by a video microscopy. Tesla-like channel ensured unidirectional liquid motion with stable pressure driven that was triggered by the interaction of Tesla valve structure and ultrasound waves. In few seconds the TUBPV can generate an accurate viscosity profile on clinic fresh blood samples from the flow time evaluation. Besides, Tesla-inspired microchannels can be used in the real-time coagulation monitoring. Discussion: These results indicate that the TUBVP can serve as a point-of-care device in the ICU to evaluate the blood's viscosity and the anticoagulation treatment.

A viscosity measurement technique for ultra-low sample volumes.

We describe a unique method to measure the viscosity of liquids based on the fluid mechanics of thin films. A drop of sample is spread over a substrate by contacting a blade with the drop and moving the blade across the substrate. The thickness of the film is determined by the capillary number, which measures the competition between the viscous force that smears the liquid over the glass slide and the surface tension that resists the deformation of the interface. We show that the length of the smear for a fixed sample volume is also set by capillary number and can be used as a reliable measure of fluid viscosity. The technique is especially suitable for viscosity measurements of biological fluids where viscosities are low and sample sizes are small. The technique can detect small changes in blood viscosity enabling it to be used as a non-specific, screening tool for diseases and therapeutic interventions.

In-situ ultrasonic viscometry of lubricants under temperature and shear

Understanding the behaviour of engine and gear oils, especially the viscosity, under temperature and shear is important to improve machine operation. A novel viscometer using ultrasound is presented and used under a range of temperatures. A single cross-temperature (between 20°C and 60°C) ultrasonic calibration is shown to be sufficient. Next, the ultrasonic viscometer is compared to a conventional viscosity measurement technique for Newtonian and non-Newtonian lubricants. Newtonian viscosity standard fluids and shear-thinning engine oils are studied. Both viscosity measurement techniques match for Newtonian fluids but ultrasonic measurements are consistently lower for shear-thinning fluids. It suggests that the ultrasonic viscometer is similar to a high-shear viscometer with a shear rate of about 106s−1.

The Role of MWCNTs in Enhancing the Foam Stability and Rheological Behavior of Cement Pastes That Contain Air-Entraining and Superplasticizer Admixtures.

This research delves into the intricate dynamics between multi-walled carbon nanotubes (MWCNTs), air-entraining admixtures (AEAs), and a range of superplasticizers (SPs) in cementitious systems, shedding light on key aspects of construction material innovation. The focus is on how MWCNTs, AEAs, and specific SPs-namely, lignosulfonate (LS), polycarboxylate (PCE), and polyacrylate (PA)-influence the stability of foams and the viscosity and setting times of cement pastes. To assess the impacts of these components, we employed foam stability assessments, viscosity measurement techniques, electrical conductivity analysis, and evaluations of dispersion and setting times. Results indicate that MWCNTs enhance foam stability and viscosity, with the degree of improvement contingent on the type and concentration of SPs and the presence of AEAs. Notably, SPs, particularly PCE and PA, markedly influence the properties of cement paste, including increasing dispersion values and modulating setting times, especially when combined with MWCNTs and AEAs. The study concludes that strategically combining MWCNTs with specific SPs and AEAs alters the physical properties of cementitious materials significantly, underscoring the potential for customizing material design in the construction sector.

Temporally and spatially resolved micro-rheometry of a transient viscous polymer formation

Real-time viscosity measurement techniques have been used to analyze the transition of hydrogels from a liquid state to a gel state. As viscosity is inversely proportional to diffusion coefficient, measuring real-time changes in viscosity can be done through passive rheometry with the addition of tracer particles. Particle diffusometry (PD) quantifies Brownian motion of sub-micron sized fluorescent particles by computing diffusion coefficients via statistical averaging. Herein, we demonstrate a method to study changes in diffusion coefficient as a function of time using PD for a temporally and spatially resolved rheometry measurement technique. We refined the PD algorithm using synthetic images of particles suspended in a liquid undergoing a sigmoidally decreasing diffusion trend to simulate the viscosity change of the solution during gelation. Then, the technique is applied to visualize the temporal and spatial gradients of diffusion coefficient during polyacrylamide hydrogel formation experiments. This work establishes the groundwork for quantifying over time changes in Brownian motion.

Multi spectroscopic and molecular simulation studies of propyl acridone binding to calf thymus DNA in the presence of electromagnetic force.

Introduction: Here, the interaction behavior between propyl acridones (PA) and calf thymus DNA (ct-DNA) has been investigated to attain the features of the binding behavior of PA with ct-DNA, which includes specific binding sites, modes, and constants. Furthermore, the effects of PA on the conformation of ct-DNA seem to be quite significant for comprehending the medicine's mechanism of action and pharmacokinetics. Methods: The project was accomplished through means of absorbance studies, fluorescence spectroscopy, circular dichroism, viscosity measurement, thermal melting, and molecular modeling techniques. Results: The intercalation of PA has been suggested by fluorescence quenching and viscosity measurements results while the thermal melting and circular dichroism studies have confirmed the thermal stabilization and conformational changes that seem to be associated with the binding. The binding constants of ct-DNA-PA complex, in the absence and presence of EMF, have been evaluated to be 6.19 × 104 M-1 and 2.95 × 104 M-1 at 298 K, respectively. In the absence of EMF, the ∆H0 and ∆S0 values that occur in the interaction process of PA with ct-DNA have been measured to be -11.81 kJ.mol-1 and 51.01 J.mol-1K-1, while in the presence of EMF they were observed to be -23.34 kJ.mol-1 and 7.49 J.mol-1K-1, respectively. These numbers indicate the involvement of multiple non-covalent interactions in the binding procedure. In a parallel study, DNA-PA interactions have been monitored by molecular dynamics simulations; their results have demonstrated DNA stability with increasing concentrations of PA, as well as calculated bindings of theoretical ΔG0. Conclusion: The complex formation between PA and ct-DNA has been investigated in the presence and absence of EMF through the multi spectroscopic techniques and MD simulation. These findings have been observed to be parallel to the results of KI and NaCl quenching studies, as well as the competitive displacement with EB and AO. According to thermodynamic parameters, electrostatic interactions stand as the main energy that binds PA to ct-DNA. Regarding the cases that involve the Tm of ct-DNA, EMF has proved to increase the stability of binding between PA and ct-DNA.

Investigation on DNA/Protein interaction of thiosemicarbazone based octahedral nickel(II) and iron(III) complexes

2-acetylpyrzine N-(4)-cyclohexylthiosemicarbazide (H2L) and its metal complexes of Ni(II) and Fe(III) have been synthesized. The structure of H2L and corresponding metal complexes are proposed based on the elemental analysis, UV-Visible, FT-IR spectroscopy, and Far IR. It is evident by means of single diffraction X-ray crystallography that there is a distortion in the octahedral geometry owing to the two units of ligands surrounding the metal ion. To exploit the medicinal potential of the complex thus synthesized, their chemical interactions with Bovine Serum Albumin and CT-DNA were studied at normal physiological conditions using UV–Visible, fluorescence spectral, and viscosity measurement techniques. The results obtained from these studies revealed that the complexes exhibit high affinity for DNA with an affinity constant of 106 M−1 and show non-covalent intercalation. The binding constant (Ka) was calculated by using UV–Visible titration from which it is inferred that Ni(II) has more affinity toward CT-DNA compared to Fe(III) complex. Also, it is established by that there were no extrinsic agents responsible for the DNA cleavage by the complexes. Also, absorption and fluorescent techniques were incorporated to study the interactivity of NiL2 and FeL2 with bovine serum albumin (BSA). In-silico methods were adapted to evaluate the DNA-complex interactions. The outcome of experimental as well as in-silico studies suggests that the metal complexes intercalate with the CT-DNA molecules.

Miscibility and thermal behavior of poly(methyl methacrylate) and polystyrene blend using benzene as a common solvent.

Polymer blending is one of the advanced technologies to attain polymeric material with tailored properties. In this work, the miscibility of Poly(methyl methacrylate) (PMMA) and Polystyrene (PS) blend in benzene was investigated by employing various techniques such as FTIR spectroscopy, viscosity measurement technique, light scattering techniques, DSC and TGA techniques over an extended range of concentrations, compositions, and temperatures. The results revealed that there exist hydrogen bonding and hydrodynamic interactions which led these polymers to get miscible to a large extent. The compatibility increased with the increasing PS contents or increase in temperature of the system. In addition, the thermal stability of blends was found to be improved with the increase in the compatibility of the polymer.

Measurements of viscosity profile in elastohydrodynamic lubrication film using fluorescence method under various contact pressure conditions

This paper describes rheological properties of hydrodynamic and elastohydrodynamic lubrication (EHL) film under various contact pressure conditions using the fluorescence measurement method. In this measurement method, the viscosity and the information about the state of the lubricant (liquid or solid) can be obtained via the analysis of fluorescence spectrum of a pyrene excimer emission. Previous research revealed that the intensity of excimer emission decreased with increasing of viscosity. In addition, the intensity ratio between the excimer peak and lubricant 5P4E fluorescence peak was introduced for the analysis, and the ratio decreased with increasing viscosity of lubricant. In this study, the viscosity profile obtained from the relationship between the intensity ratio and viscosity showed that the state of lubricant in the lubrication film corresponded almost exactly to the lubrication regime proposed in previous researches. It is concluded that the viscosity measurement technique proposed in this study is useful method for practical uses in hydrodynamic and elastohydrodynamic conditions, while in the high viscosity range, the measured viscosity varies widely due to the variation of intensity ratio.

An Electromechanical <i>In Situ</i> Viscosity Measurement Technique for Shear Thickening Fluids

This paper presents the feasibility of developing an electromechanical in-situ viscosity measurement technique by analyzing the detectability of small variations in the viscosity of different shear thickening fluids and their different compositions. Shear thickening fluid (STF) is a kind of non-Newtonian fluid showing an increasing viscosity profile under loading. STF is utilized in several applications to take advantage of its tunable rheology. However, process control in different STF applications requires rheological measurements, which cause a costly investment and long-lasting labor. Therefore, one of the most commonly used in-situ structural health monitoring techniques, electromechanical impedance (EMI), was used in this study. In order to actuate the medium electromechanically, a piezoelectric wafer active sensor (PWAS) was used. The variations in the spectral response of PWAS resonator that can be submerged into shear thickening fluid are analyzed by the root mean square deviation, mean absolute percentage deviation and correlation coefficient deviation. According to the results, EMI metrics provide good correlations with the rheological parameters of STF and thereby enabling quick and low-cost rheological control for STF applications such as vibration dampers or stiffness control systems.

Comparison of setups for measuring the viscosity of coal ash slags for entrained-flow gasification

A coal ash and a process slag from an entrained-flow gasifier were analyzed by two institutes in their respective workflow to compare viscosity measurement techniques under reducing conditions. Several analyses were carried out to characterize the samples, including X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy with an energy-dispersive X-ray detector (SEM-EDX). The results are compared to the phases predicted based on thermochemical calculations. A coal slag (S1) was analyzed as exhibiting Newtonian behavior by one institute, while it showed shear-thickening behavior at another institute due to crystallization. This was confirmed by XRD and SEM-EDX. In contrast to previous studies, the sample in this work was still glassy at a low shear rate. The phase compositions of the crystallized slags were in good agreement with thermochemical predictions. The process slag (S2) sample showed shear-thinning behavior but was of very high viscosity, meaning that the measurement was restricted by instrumental limitations. The chemical compositions of the slags obtained after viscosity measurements indicated contamination with crucible material (Mo) for S1, while the composition of S2 was the same before and after viscosity measurements. The overall relative difference in the measurements considering both measurement routines and both samples was ±22%.

Lees–Edwards boundary conditions for translation invariant shear flow: Implementation and transport properties

Molecular dynamics (MD) simulations represent a powerful investigation tool in the field of soft matter. By using shear flows, one can probe the bulk rheology of complex fluids, also beyond the linear response regime, in a way that imitates laboratory experiments. One solution to impose a shear flow in particle-based simulations is the Lees–Edwards technique, which ensures that particles experience shear by imposing rules for motion and interactions across the boundary in the direction of the shear plane. Despite their presentation in 1972, a readily available public implementation of Lees–Edwards boundary conditions has been missing from MD simulation codes. In this article, we present our implementation of the Lees–Edwards technique and discuss the relevant technical choices. We used ESPResSo, the extensible simulation package for research on soft matter, for molecular dynamics simulations which can be used as a reference for other implementers. We illustrate our implementation using bulk dissipative particle dynamics fluids, compare different viscosity measurement techniques, and observe the anomalous diffusion in our samples during continuous and oscillatory shear, in good comparison with theoretical estimates.

Two-dimensional fluid viscosity measurement in microchannel flow using fluorescence polarization imaging

This study describes the development of a noncontact and two-dimensional fluid viscosity measurement technique based on fluorescence polarization microscopy. This technique exploits fluorescence depolarization due to rotational Brownian motion of fluorophores and determines fluid viscosity in microchannel flow by measuring steady-state fluorescence polarization. The main advantage of the technique is that planar distributions of fluid viscosity can be visualized by noncontact optical measurement, while commonly-used mechanical viscometers measure the viscosity of bulk liquids. Moreover, steady-state polarization measurements are realized using a simpler experimental setup compared to other noncontact techniques such as time-resolved fluorescence lifetime/polarization measurements. The relationship between the fluid viscosity (μ) and the fluorescence polarization degree (P) was experimentally obtained using casein molecules labeled with fluorescein isothiocyanate as a fluorescent probe. The fluid viscosity was controlled within the range of 0.7–3.0 mPa s, which is the range often encountered in biological materials, by mixing sucrose or glucose with the solution. The fluid temperature was maintained uniform at 30 °C during the measurement. The calibration result showed that 1/P linearly increased with 1/μ which qualitatively agreed well with the theoretical prediction. The measurement uncertainty was 7.5%–9.5% based on the slope of the calibration curve. The viscosity gradient generated by the mass diffusion between the two solutions co-flowing in the Y-shaped microchannel was clearly visualized under uniform temperature conditions by applying the calibration curve. Finally, the influence of the temperature change on P was experimentally evaluated. The results supported the applicability of the present technique for visualization of the viscosity distribution induced by temperature change. These results confirmed the feasibility of the present technique for analyzing microscale viscosity fields associated with mass transport or temperature change.

Combined experimental and computational studies on molecular structure of nickel complex of 4-amino-N-(1, 3-thiazol-2-yl) benzenesulfonamide with coordinated pyridine

Synthesis of the Ni(II) complex of sulfathiazole was carried out and the crystal structure was determined independently. The various vibration patterns of ligand and its Ni(II) complex are studied by IR spectroscopy. Also, the optimized geometry of the complex is derived from DFT/B3LYP calculations and the results are compared with the experimental one. Bond strengths and first hyperpolarizability of the complex are studied by NBO and NLO analysis, respectively. Also, the molecular properties such as charge transfer are clarified using MPA and FMO analysis. The visualized and correlated in a novel way through qualitative analysis using the Hirshfeld surface and 3 D energy frameworks are performed for the complex. The Ni-STZ complex is studied for the binding properties with CT-DNA employing UV-Vis and viscosity measurement techniques. The molecular docking analyses corroborate well the experimental results of DNA binding. Also, the toxicity of the complex is performed on brine shrimp bioassay.

A micropillar-based microfluidic viscometer for Newtonian and non-Newtonian fluids

In this study, a novel viscosity measurement technique based on measuring the deflection of flexible (poly) dimethylsiloxane (PDMS) micropillars is presented. The experimental results show a nonlinear relationship between fluid viscosity and the deflection of micropillars due to viscoelastic properties of PDMS. A calibration curve, demonstrating this nonlinear relationship, is generated, and used to determine the viscosity of an unknown fluid. Using our method, viscosity measurements for Newtonian fluids (glycerol/water solutions) can be performed within 2–100 cP at shear rates γ = 60.5–398.4 s−1. We also measured viscosity of human whole blood samples (non-Newtonian fluid) yielding 2.7–5.1 cP at shear rates γ = 120–345.1 s−1, which compares well with measurements using conventional rotational viscometers (3.6–5.7 cP). With a sensitivity better than 0.5 cP, this method has the potential to be used as a portable microfluidic viscometer for real-time rheological studies.

The effect of magnetized water on the oxidation reaction of phenol derivatives and aromatic amines by horseradish peroxidase enzyme.

The present study aimed to investigate, for the first time, the rate of the oxidation reaction of some derivatives of phenol and aromatic amines, that is, pyrogallol, catechol, resorcinol, ortho-aminophenol, meta-aminophenol, para-aminophenol, ortho-phenylenediamine, and para-phenylenediamine, in the presence of hydrogen peroxide in pure and magnetized solvents using horseradish peroxidase enzyme. The reaction was studied in the absence and presence of a magnetized solvent under completely identical conditions. The results showed that magnetized solvent could change the structure of the enzyme and reduce its activity. In addition, it affected the rate of oxidation of the selected derivatives through altering the strength of the hydrogen bonds of the system. The changes in the structure and activity of the enzyme were examined using UV-Vis and fluorescence spectroscopy as well as viscosity measurement technique. Examination of the secondary structure via the far UV-CD spectrum indicated the increase in the alpha helical structure in the magnetized solvent. When dissolved in a magnetized solvent, hydrogen peroxide as an enzyme substrate reduced the rate of enzymatic reaction and provided lower saturation conditions for the enzyme compared with when it was dissolved in the pure solvent.

Design, synthesis, spectral characterization, DNA binding, photo cleavage and antibacterial studies of transition metal complexes of benzothiazole Schiff base

Abstract In the present work, a series of Benzothiazole based Schiff base ligand 2-((E)-(6-ethoxybenzo[d]thiazol-2-ylimino)methyl)-4-nitrophenol and their Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) complexes were synthesized and characterized by physical, analytical and spectral data such as elemental analysis, FT-IR, 1H NMR, 13C NMR, ESI-Mass, UVvis, powder XRD, SEM and EDX studies. Based on spectro-analytical experimental data a square planar geometry is confirmed for all these metal complexes. The synthesized Schiff base acts as monobasic bi-dentate ligand which coordinates through imine nitrogen and phenolic oxygen atom to the metal. The metal complexes studies here include interaction of DNA binding studies with CT (Calf thymus) DNA through an intercalative mode. The DNA binding properties of metal complexes have been investigated by using UV–vis electron absorption spectroscopy, fluorescence emission spectra and viscosity measurement techniques. DNA photo cleavage ability evaluated by agarose gel electrophoresis method their transition metal complexes. Moreover, the antibacterial studies five bacterial species was evaluated for metal complexes. Cytotoxicity studies of Schiff base ligand and their metal complexes have been also investigated.

Effect of salinity on adsorption and interaction forces of hydrophobically modified polyacrylamide on silica and alumina surfaces

In this work, the adsorption behaviors and interaction forces of different polymers on silica and alumina surfaces have been investigated under the effect of KCl concentration using quartz crystal micro-balance with dissipation (QCM-D) monitoring technique, viscosity measurement and atomic force microscopy (AFM) colloidal probe technique. Polyacrylamide (PAM) and hydrophobically modified polyacrylamide (HMPAM) with hydrophobic monomer (i.e., hexadecyl dimethyl allyl ammonium chloride (C16DMAAC)) have been investigated as model polymers. It is found that the adsorption amounts of HMPAM and PAM polymers on negatively charged silica and positively charged alumina surfaces increase with increasing solution salinity (1–100 mM KCl). HMPAM displays higher adsorption capacity than PAM on both silica and alumina surfaces, which is attributed to the hydrophobic interaction originated from the long hydrocarbon chains of HMPAM. Furthermore, the measured adhesion between the polymers and the substrate surfaces is found to decrease for the alumina cases and increase for the silica cases with increasing the salinity, which is due to the weakened electrostatic interactions between the polymers and substrate surfaces under high salinity (i.e., 100 mM KCl). The viscosities of PAM and HMPAM solutions are found to decrease with increasing solution salinity, which could be caused by the much more coiled conformation of PAM and HMPAM chains at higher salinity. Both the interactions between the polymer and substrate surface and the polymer conformational changes play important roles in the polymer adsorption behaviors on silica and alumina surfaces.

Palladium(II) complexes with salicylaldehyde ligands: Synthesis, characterization, structure, in vitro and in silico study of the interaction with calf-thymus DNA and albumins

The synthesis and characterization of four palladium(II) complexes with substituted salicylaldehydes (X-saloH) having the general formula [Pd(X-salo)2] was undertaken. The complexes are formulated as [Pd(3-OCH3-salo)2] 1, [Pd(5-NO2-salo)2] 2, [Pd(5-Cl-salo)2] 3, and [Pd(5-Br-salo)2] 4. The structure of complex 1 was verified by single-crystal X-ray crystallography. Spectroscopic (UV–vis), and physicochemical (viscosity measurements) techniques were employed in order to study the binding of the complexes with calf-thymus (CT) DNA, while ethidium bromide (EB) displacement studies, performed by fluorescence emission spectroscopy, revealed the ability of the complexes to displace the DNA-bound EB. Intercalation is the most possible mode of interaction of the complexes with CT DNA. The interaction of the complexes with bovine (BSA) and human (HSA) serum albumin proteins was studied by fluorescence emission spectroscopy and the relatively high binding constants revealed the reversible binding of the complexes to the albumins. Molecular docking simulations on the crystal structure of HSA, BSA and CT DNA were employed in order to study in silico the ability of the studied complexes 1–4 to bind to these target macromolecules.