scholarly journals Effects of Ionic Strength on Lateral Particle Migration in Shear-Thinning Xanthan Gum Solutions

Micromachines ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 535 ◽  
Author(s):  
Mira Cho ◽  
Sun Ok Hong ◽  
Seung Hak Lee ◽  
Kyu Hyun ◽  
Ju Min Kim
Keyword(s):  
Ionic Strength ◽  
Rheological Properties ◽  
Viscoelastic Fluid ◽  
Xanthan Gum ◽  
Viscoelastic Fluids ◽  
Shear Thinning ◽  
Particle Migration ◽  
Cell Counting ◽  
Contour Length ◽  
Wide Range

Viscoelastic fluids, including particulate systems, are found in various biological and industrial systems including blood flow, food, cosmetics, and electronic materials. Particles suspended in viscoelastic fluids such as polymer solutions migrate laterally, forming spatially segregated streams in pressure-driven flow. Viscoelastic particle migration was recently applied to microfluidic technologies including particle counting and sorting and the micromechanical measurement of living cells. Understanding the effects on equilibrium particle positions of rheological properties of suspending viscoelastic fluid is essential for designing microfluidic applications. It has been considered that the shear-thinning behavior of viscoelastic fluid is a critical factor in determining the equilibrium particle positions. This work presents the lateral particle migration in two different xanthan gum-based viscoelastic fluids with similar shear-thinning viscosities and the linear viscoelastic properties. The flexibility and contour length of the xanthan gum molecules were tuned by varying the ionic strength of the solvent. Particles suspended in flexible and short xanthan gum solution, dissolved at high ionic strength, migrated toward the corners in a square channel, whereas particles in the rigid and long xanthan gum solutions in deionized water migrated toward the centerline. This work suggests that the structural properties of polymer molecules play significant roles in determining the equilibrium positions in shear-thinning fluids, despite similar bulk rheological properties. The current results are expected to be used in a wide range of applications such as cell counting and sorting.

scholarly journals Effect of ionic strength on shear-thinning nanoclay–polymer composite hydrogels

2018 ◽  
Vol 6 (8) ◽  
pp. 2073-2083 ◽  
Author(s):  
Amir Sheikhi ◽  
Samson Afewerki ◽  
Rahmi Oklu ◽  
Akhilesh K. Gaharwar ◽  
Ali Khademhosseini
Keyword(s):  
Ionic Strength ◽  
Rheological Properties ◽  
Polymer Composite ◽  
Biomedical Applications ◽  
Shear Thinning ◽  
Composite Hydrogels ◽  
Polymer Interactions ◽  
Fundamental Insight ◽  
Insight Into

The effect of ionic strength on the structure and rheological properties of nanoclay–gelatin shear-thinning biomaterials (STBs) is investigated. A fundamental insight into nanoclay–polymer interactions in physiological environments is provided to design clay-based biomaterials for biomedical applications.

Rheological Characteristics of Surfactant-Based Fluids: A Comprehensive Study

2018 ◽  
Author(s):  
Ahmed H. Kamel
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Rheological Behavior ◽  
Surfactant Concentration ◽  
Flow Direction ◽  
Shear Thinning ◽  
Molecular Structures ◽  
Wide Range ◽  
Unique Nature ◽  
Viscoelastic Surfactant

Surfactant-based fluids, SB fluids exhibit complex rheological behavior due to substantial structural change caused by the molecules self-assembled colloidal aggregation. Various factors affect their rheological properties. Among these factors, surfactant concentration, shear rate, temperature, and salinity are investigated. One of the most popular surfactants, Aromox® APA-T viscoelastic surfactant (VES) is examined. The study focuses on four different concentrations (1.5%, 2%, 3%, and 4%) over a shear rate ranging from 0.0526 sec−1 to 1944 sec−1 using Bohlin rheometer. For salinity effects, two brine solutions are used; 2 and 4% KCl while for temperature effects, a wide range from ambient temperature of 72°F up to 200°F is covered. The results show that SB fluids exhibit a complex rheological behavior due to its unique nature and the various structures form in the solution. In general, SB fluids at all concentrations exhibit a non-Newtonian pseudo-plastic shear thinning behavior. As the surfactant concentration and/or shear increases, a stronger shear thinning behavior can be seen. Increasing solution salinity promotes formation of rod-like micelles and increases its flexibility. Salinity affects micelles’ growth and their rheological behavior is very sensitive to the nature and structure of the added salt. Different molecular structures are formed; spherical micelles occur first and then increased shear rate and/or salinity promotes the formation of rod-like micelles. Later, rod-like micelles are aligned in the flow direction and form a large super ordered structure of micellar bundles or aggregates called shear induced structure (SIS). Different structures implies different rheological properties. Likewise, rheology improves with increasing temperature up to 100°F. Further increase in temperature reverses the effects and viscosity decreases. However, the effects of temperature and salinity diminish at higher shear rates. Furthermore, a rheology master curve is developed to further understand the rheological behavior of SB fluids and correlate rheological properties to its microscopic structure.

scholarly journals Dynamics of particle migration in channel flow of viscoelastic fluids

2015 ◽  
Vol 785 ◽  
pp. 486-505 ◽  
Author(s):  
Gaojin Li ◽  
Gareth H. McKinley ◽  
Arezoo M. Ardekani
Keyword(s):  
Channel Flow ◽  
Fluid Transport ◽  
Shear Thinning ◽  
Secondary Flows ◽  
Particle Migration ◽  
Scaling Analysis ◽  
Inertial Effects ◽  
Particle Focusing ◽  
Start Up ◽  
Wide Range

The migration of a sphere in the pressure-driven channel flow of a viscoelastic fluid is studied numerically. The effects of inertia, elasticity, shear-thinning viscosity, secondary flows and the blockage ratio are considered by conducting fully resolved direct numerical simulations over a wide range of parameters. In a Newtonian fluid in the presence of inertial effects, the particle moves away from the channel centreline. The elastic effects, however, drive the particle towards the channel centreline. The equilibrium position depends on the interplay between the elastic and inertial effects. Particle focusing at the centreline occurs in flows with strong elasticity and weak inertia. Both shear-thinning effects and secondary flows tend to move the particle away from the channel centreline. The effect is more pronounced as inertia and elasticity effects increase. A scaling analysis is used to explain these different effects. Besides the particle migration, particle-induced fluid transport and particle migration during flow start-up are also considered. Inertial effects, shear-thinning behaviour, and secondary flows are all found to enhance the effective fluid transport normal to the flow direction. Due to the oscillation in fluid velocity and strong normal stress differences that develop during flow start-up, the particle has a larger transient migration velocity, which may be potentially used to accelerate the particle focusing.

Rheological Properties of Limited Enzymatic Hydrolyzed Wheat Gluten

2012 ◽  
Vol 550-553 ◽  
pp. 1535-1539
Author(s):  
Zhang Cun Wang ◽  
Le Jing Li ◽  
Xue Wei Zhao ◽  
Sheng Wen Cui
Keyword(s):  
Rheological Properties ◽  
Sodium Alginate ◽  
Apparent Viscosity ◽  
Xanthan Gum ◽  
Wheat Gluten ◽  
Shear Thinning ◽  
Effects Of Temperature ◽  
Complex Solutions

The rheological properties of Limited Enzyme-hydrolyzed Wheat Gluten (LHWG) and its complex solutions with xanthan gum (XG), sodium alginate (SA) or gelatin were researched by Brookfield DV-Ⅱ+Pro Viscometer. The results showed that they all exhibited typical shear-thinning behavior and the higher LHWG concentration, the more evident of the shear thinning was. The effects of temperature on the rheology of LHWG were very complicated based on the concentration. The apparent viscosity of 300 mg/mL LHWG (20°C) was higher than that of 100 mg/mL and 200 mg/mL, and showed fluctuation between 20°C and 90°C, which were strongly different from that of low LHWG solution. However, the rheological properties of LHWG were influenced slightly by shearing time.

Influence of pH and ionic strength on the physical and rheological properties and stability of whey protein stabilized o/w emulsions containing xanthan gum

2019 ◽  
Vol 242 ◽  
pp. 141-152 ◽  
Author(s):  
Jiratthitikan Sriprablom ◽  
Pairoj Luangpituksa ◽  
Jirarut Wongkongkatep ◽  
Thunyarat Pongtharangkul ◽  
Manop Suphantharika
Keyword(s):  
Ionic Strength ◽  
Rheological Properties ◽  
Whey Protein ◽  
Xanthan Gum ◽  
Influence Of Ph

Control of Mass Flow-Rate of Viscoelastic Fluids Through Time-Periodic Electro-Osmotic Flows in a Microchannel

2021 ◽  
Author(s):  
Sayantan Dawn ◽  
Sandip Sarkar
Keyword(s):  
Electric Field ◽  
Mass Flow Rate ◽  
Double Layer ◽  
Viscoelastic Fluid ◽  
Mass Flow ◽  
Flow Rate ◽  
Electric Double Layer ◽  
Viscoelastic Fluids ◽  
Shear Thinning ◽  
Time Periodic

Abstract In the present research, we address the implications of the pulsating electric field on controlling mass flow-rate characteristics for the time-periodic electro-osmotic flow of a viscoelastic fluid through a microchannel. Going beyond the Debye-Hückel linearization for the potential distribution inside the Electric Double Layer, the Phan-Thien-Tanner constitutive model is employed to describe the viscoelastic behaviour of the fluid. The analytical/semi-analytical expressions for the velocity distribution corresponding to a steady basic part, and a transient perturbed part are obtained by considering periodic pulsations in the applied electrical field. Our results based on sinusoidal pulsations reveal that enhanced shear thinning characteristics of the viscoelastic fluids show higher amplitude of pulsations with the oscillations in the velocity gradients primarily contrived within the Electric Double Layer region. The amplitude of mass flow rates increases with increasing the viscoelastic parameter , whereas, the phase lag displays a reverse trend. The analysis for an inverse problem is extended where the required magnitude of electric field pulsations for a target mass flow rate in the form of sinusoidal pulsations. It is found that with increasing shear-thinning characteristics of the viscoelastic fluid, there is a progressive reduction in the required electric field strength to maintain an aimed mass flow rate. Besides, required electric fields for controlled mass flow with triangular and trapezoidal pulsations are also determined.

Rheological Properties of Methane Hydrate Slurry in the Presence of Xanthan Gum

SPE Journal ◽  
2020 ◽  
Vol 25 (05) ◽  
pp. 2341-2352 ◽  
Author(s):  
Weiqi Fu ◽  
Zhiyuan Wang ◽  
Baojiang Sun ◽  
Jianchun Xu ◽  
Litao Chen ◽  
...  
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Newtonian Fluid ◽  
Methane Hydrate ◽  
Xanthan Gum ◽  
Drilling Fluid ◽  
Hydrate Formation ◽  
Shear Thinning ◽  
Shear Rates ◽  
Blowout Preventer

Summary Methane hydrate formation in a xanthan-gum (XG) solution is an important problem for drilling in a deepwater environment. It not only alters the rheology of the drilling fluid in the wellbore but increases the risks of a hydrate blockage in the blowout preventer. The current work is performing groups of experiments to investigate the rheology of the hydrate slurry under XG concentrations of 0.15, 0.2, 0.25, and 0.3%, shear rates from 10 to 480 s−1, and hydrate concentrations from 1.01 to 9.12%. The experimental results show that the hydrate slurry with XG additives exhibits an obvious shear-thinning behavior, which is because the XG solution has strong pseudoplastic characteristics, and the inner structures of the flocculated hydrate particles suspended in the hydrate slurry are broken up during the hydrate-slurry flow. The increase of hydrate concentrations in the hydrate slurry can reduce the non-Newtonian fluid index and make the rheology of the hydrate slurry become more shear-thinning. However, as the XG concentration increases in the hydrate slurry, the influence of the hydrate concentration on the rheology of the hydrate slurry gradually weakens. Empirical Herschel–Bulkley-type equations are developed to describe the rheology of the hydrate slurry with XG for the current experimental condition, considering the shear rate, hydrate concentration, and XG concentration. In the proposed equations, the non-Newtonian factor and the consistency factor are expressed as functions of XG concentration empirically. Correction Notice:The preprint version of this paper was modified from its original version to correct Figs. 8 and 9 and Eqs. 6 through 9 on page 7. Errata explaining the corrections are included below as Supporting Information.

scholarly journals Particle Focusing under Newtonian and Viscoelastic Flow in a Straight Rhombic Microchannel

Micromachines ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 998
Author(s):  
Joo-Yong Kwon ◽  
Taehoon Kim ◽  
Jungwoo Kim ◽  
Younghak Cho
Keyword(s):  
Newtonian Fluid ◽  
Microelectromechanical Systems ◽  
Viscoelastic Fluids ◽  
Newtonian Fluids ◽  
Particle Migration ◽  
Inertial Particles ◽  
Cross Sectional ◽  
Double Line ◽  
Particle Focusing ◽  
Wide Range

Particle behavior in viscoelastic fluids has attracted considerable attention in recent years. In viscoelastic fluids, as opposed to Newtonian fluids, particle focusing can be simply realized in a microchannel without any external forces or complex structures. In this study, a polydimethylsiloxane (PDMS) microchannel with a rhombic cross-sectional shape was fabricated to experimentally investigate the behavior of inertial and elasto-inertial particles. Particle migration and behavior in Newtonian and non-Newtonian fluids were compared with respect to the flow rate and particle size to investigate their effect on the particle focusing position and focusing width. The PDMS rhombic microchannel was fabricated using basic microelectromechanical systems (MEMS) processes. The experimental results showed that single-line particle focusing was formed along the centerline of the microchannel in the non-Newtonian fluid, unlike the double-line particle focusing in the Newtonian fluid over a wide range of flow rates. Numerical simulation using the same flow conditions as in the experiments revealed that the particles suspended in the channel tend to drift toward the center of the channel owing to the negative net force throughout the cross-sectional area. This supports the experimental observation that the viscoelastic fluid in the rhombic microchannel significantly influences particle migration toward the channel center without any external force owing to coupling between the inertia and elasticity.

Effect of ionic strength on assembly behaviors and rheological properties of rice glutelin based fibrils

2021 ◽  
pp. 103224
Author(s):  
Ting Li ◽  
Li Wang ◽  
Xinxia Zhang ◽  
Peibin Yu ◽  
Zhengxing Chen
Keyword(s):  
Ionic Strength ◽  
Rheological Properties
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