scholarly journals Effect of pH on Effective Slip Length and Surface Charge at Solid–Oil Interfaces of Roughness-Induced Surfaces

Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 752
Author(s):  
Porui Tian ◽  
Yifan Li
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Ph Value ◽  
Slip Length ◽  
Boundary Slip ◽  
Effect Of Ph ◽  
Effective Boundary ◽  
Effective Slip Length ◽  
Effective Slip

In the development of micro/nano fluid control systems, fluid resistance has always been one of the key factors restricting its development. According to previous studies, it is found that the boundary slip effect of the solid-liquid interface can effectively reduce the resistance of the microfluid and improve the transport efficiency of the microfluid. The boundary slip length is mainly affected by surface wettability, roughness, and surface charge density. Among them, the influence mechanism of surface charge density on the boundary slip is the most complicated, and there is a lack of relevant research, and further investigation is needed. In this paper, we present research on quantification of effective slip length and surface charge density, where the roughness effect is considered. The electrostatic and hydrodynamic force data obtained from atomic force microscopy (AFM) measurements were fitted and processed for comparative analysis. We obtained the variation of surface charge density and effective slip length when different oleophobic surface samples were immersed in ethylene glycol with different pH values. The effect of pH on the surface charge density and effective slip length was investigated by their variations. The mechanism of the effect of pH on the surface charge density was discussed. The experimental results show that in the ethylene glycol solution, no matter whether the pH value of the solution increases or decreases, the charge density of the surface with the same properties decreases, and the effective boundary slip length also shows a downward trend. In deionized water, the surface charge density and effective boundary slip length decreases with the decrease of PH value.

scholarly journals The study of surface wetting, nanobubbles and boundary slip with an applied voltage: A review

2014 ◽  
Vol 5 ◽  
pp. 1042-1065 ◽  
Author(s):  
Yunlu Pan ◽  
Bharat Bhushan ◽  
Xuezeng Zhao
Keyword(s):  
Contact Angle ◽  
Fluid Flow ◽  
Charge Density ◽  
Surface Charge ◽  
Liquid Flow ◽  
Applied Voltage ◽  
Surface Charge Density ◽  
Slip Length ◽  
Surface Wetting ◽  
Boundary Slip

The drag of fluid flow at the solid–liquid interface in the micro/nanoscale is an important issue in micro/nanofluidic systems. Drag depends on the surface wetting, nanobubbles, surface charge and boundary slip. Some researchers have focused on the relationship between these interface properties. In this review, the influence of an applied voltage on the surface wettability, nanobubbles, surface charge density and slip length are discussed. The contact angle (CA) and contact angle hysteresis (CAH) of a droplet of deionized (DI) water on a hydrophobic polystyrene (PS) surface were measured with applied direct current (DC) and alternating current (AC) voltages. The nanobubbles in DI water and three kinds of saline solution on a PS surface were imaged when a voltage was applied. The influence of the surface charge density on the nanobubbles was analyzed. Then the slip length and the electrostatic force on the probe were measured on an octadecyltrichlorosilane (OTS) surface with applied voltage. The influence of the surface charge on the boundary slip and drag of fluid flow has been discussed. Finally, the influence of the applied voltage on the surface wetting, nanobubbles, surface charge, boundary slip and the drag of liquid flow are summarized. With a smaller surface charge density which could be achieved by applying a voltage on the surface, larger and fewer nanobubbles, a larger slip length and a smaller drag of liquid flow could be found.

Surface potential and conductance induced in lipid bilayers by the negatively charged ionophore Br-X537A

1982 ◽  
Vol 60 (1) ◽  
pp. 42-48 ◽  
Author(s):  
G. Roy ◽  
Y. Okada ◽  
R. Laprade
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Lipid Bilayers ◽  
Concentration Dependence ◽  
Surface Potential ◽  
Surface Charge Density ◽  
Ph Dependence ◽  
Neutral Molecule ◽  
Effect Of Ph

The adsorption of Br-X537A and its effect on the surface potential of monoolein lipid bilayers was measured using the nonactin conductance as a probe to determine the surface charge density. Because of the pH dependence of this adsorption, it was concluded that not only the negatively charged molecules X− could induce a surface charge but also a dimer HX2− made from X− and the neutral molecule HX. Also an important bilayer conductance was induced by Br-X537A. From the Br-X537A concentration dependence of this conductance, the effect of pH, and the induced surface potential, it was found that two charged complexes are transported across the bilayer depending on pH. At pH ≥ 7 the conducting molecule is X− and at pH ≤ 5 the complex is H2X3−. A quantitive model is obtained to calculate both the induced surface potential and the conductance.

Quantification of Surface Charge Density and Its Effect on Boundary Slip

Langmuir ◽  
2013 ◽  
Vol 29 (23) ◽  
pp. 6953-6963 ◽  
Author(s):  
Dalei Jing ◽  
Bharat Bhushan
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Boundary Slip

scholarly journals Interface conditions of roughness-induced superoleophilic and superoleophobic surfaces immersed in hexadecane and ethylene glycol

2017 ◽  
Vol 8 ◽  
pp. 2504-2514 ◽  
Author(s):  
Yifan Li ◽  
Yunlu Pan ◽  
Xuezeng Zhao
Keyword(s):  
Surface Roughness ◽  
Slip Length ◽  
Theoretical Description ◽  
Interface Roughness ◽  
Real Surface ◽  
Interface Conditions ◽  
Boundary Slip ◽  
Effective Slip Length ◽  
Effective Slip ◽  
Underlying Mechanisms

Interface conditions are an important property that can affect the drag of fluid flow. For surfaces with different oleophobicity, the boundary slip at the solid–oil interface is mostly larger than that at the solid–water interface. Roughness is a key factor for the wettability of superoleophilic/superoleophobic surfaces, and it has been found to affect the effective value of slip length in measurements. Moreover, there are no studies on the effect of roughness on slip at interfaces between oil and superoleophilic/superoleophobic surfaces. A theoretical description of the real surface roughness is yet to be found. Results show that the effective slip length is negative and decreases with an increasing root mean squared (RMS) roughness of surfaces, as the increasing roughness enhances the area with discontinuous slip at the solid–liquid interface. The underlying mechanisms are analyzed. The amplitude parameters of surface roughness could significantly inhibit the degree of boundary slip on both superoleophilic surfaces in Wenzel state and superoleophobic surfaces in Cassie state immersed in oil. The oleic systems were likely to enhance boundary slip and resulted in a corresponding reduction in drag with decreasing roughness on the solid–oil interfaces.

scholarly journals Slip length and structure of liquid water flowing past atomistic smooth charged walls

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xinran Geng ◽  
Miao Yu ◽  
Wei Zhang ◽  
Qiwei Liu ◽  
Xiaopeng Yu ◽  
...  
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Interaction Energy ◽  
Liquid Water ◽  
Surface Charge Density ◽  
Slip Length ◽  
Static Structure Factor ◽  
Charged Surface ◽  
Static Structure ◽  
The Relationship

AbstractIn this work, the slip behavior and structure of liquid water flowing between two charged solid planar walls were investigated using non-equilibrium molecular dynamics simulations. The upper and lower walls are positive and negative charged, respectively. It was shown that the slip length increases at smaller water-solid interaction energy and become smaller with increasing the surface charge density. At the largest surface charge density, the slip length nearly independent of the water-solid interaction energy. The relationship between the slip length and surface charge density and water-solid interaction energy was rationalized by considering the static structure factor of liquid water. Interestingly, the positive charged surface induces less ordering structure and larger slip at the small surface charge density than that by the negative charged surface. While, at large surface charge density, the opposite correlation is observed. Furthermore, we find that the relationship between the slip length and the normalized main peak of static structure factor collapses onto a single curve for different water-solid interaction energies and surface charge densities. The results of the present work open perspectives for modeling complex systems with combined effects of surface charge and wettability.

scholarly journals Mapping Surface Charge Distribution of Single-Cell via Charged Nanoparticle

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1519
Author(s):  
Leixin Ouyang ◽  
Rubia Shaik ◽  
Ruiting Xu ◽  
Ge Zhang ◽  
Jiang Zhe
Keyword(s):  
Cell Surface ◽  
Charge Density ◽  
Surface Charge ◽  
Charge Distribution ◽  
Surface Charge Density ◽  
Single Cells ◽  
Fluorescent Light ◽  
Fluorescent Nanoparticles ◽  
Cell Surface Charge ◽  
Surface Charge Distribution

Many bio-functions of cells can be regulated by their surface charge characteristics. Mapping surface charge density in a single cell’s surface is vital to advance the understanding of cell behaviors. This article demonstrates a method of cell surface charge mapping via electrostatic cell–nanoparticle (NP) interactions. Fluorescent nanoparticles (NPs) were used as the marker to investigate single cells’ surface charge distribution. The nanoparticles with opposite charges were electrostatically bonded to the cell surface; a stack of fluorescence distribution on a cell’s surface at a series of vertical distances was imaged and analyzed. By establishing a relationship between fluorescent light intensity and number of nanoparticles, cells’ surface charge distribution was quantified from the fluorescence distribution. Two types of cells, human umbilical vein endothelial cells (HUVECs) and HeLa cells, were tested. From the measured surface charge density of a group of single cells, the average zeta potentials of the two types of cells were obtained, which are in good agreement with the standard electrophoretic light scattering measurement. This method can be used for rapid surface charge mapping of single particles or cells, and can advance cell-surface-charge characterization applications in many biomedical fields.

Triboelectrification of nanocomposites using identical polymer matrixes with different concentrations of nanoparticle fillers

2021 ◽  
Author(s):  
Linards Lapčinskis ◽  
Artis Linarts ◽  
Kaspars Mālnieks ◽  
Hyunseung Kim ◽  
Kristaps Rubenis ◽  
...  
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Polymer Layers

In this study, we investigate triboelectrification in polymer-based nanocomposites using identical polymer matrixes containing different concentrations of nanoparticles (NPs). The triboelectric surface charge density on polymer layers increased as the...

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