Electrokinetic Microflow Instability With Conductivity Gradients

2003 ◽  
Author(s):  
Chuan-Hua Chen ◽  
Hao Lin ◽  
Sanjiva K. Lele ◽  
Juan G. Santiago
Keyword(s):  
Electric Field ◽  
Convective Instability ◽  
Flow Instability ◽  
Microfluidic Channels ◽  
Charge Accumulation ◽  
Electrokinetic Flow ◽  
Dc Electric Field ◽  
Bulk Charge ◽  
First Time ◽  
And Diffusion

We have experimentally identified and quantified an electrokinetic flow instability that occurs in DC-electric-field driven microfluidic channels with significant conductivity gradients. We have, for the first time, developed a physical model for this instability which captures the interactions between bulk charge accumulation, electromigration, convection, and diffusion. A linear stability analysis based on this model captures key physics of this convective instability with a threshold electric field. The model and experiments show conductivity gradients and their associated bulk charge accumulation are crucial for such instabilities.

scholarly journals Передача крутящего момента проводящей частице с использованием силы Лоренца

2022 ◽  
Vol 56 (1) ◽  
pp. 76
Author(s):  
А.И. Грачев
Keyword(s):  
Dipole Moment ◽  
Electric Field ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Field Application ◽  
Conductive Particle ◽  
Particle Rotation ◽  
Dc Electric Field ◽  
First Time ◽  
Cylindrical Particles

In the paper the concept of conductive particle rotation in DC electric field with including the Lorentz force providing generation of electric dipole moment of the particle is for the first time discussed. Some models of the torque transfer to spherical and cylindrical particles based on of the Hall effect at usual geometry and with additional electric field application and also in the case of implementation of the photoelectromagnetic effect are presented.

scholarly journals Linear Assembles of BN Nanosheets, Fabricated in Polymer/BN Nanosheet Composite Film

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Hong-Baek Cho ◽  
Tadachika Nakayama ◽  
Tsuneo Suzuki ◽  
Satoshi Tanaka ◽  
Weihua Jiang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electric Field ◽  
Composite Film ◽  
High Speed ◽  
Film Plane ◽  
Digital Microscopy ◽  
X Ray Diffraction ◽  
High Anisotropy ◽  
Dc Electric Field ◽  
First Time

Linear assembles of BN nanosheets (LABNs) were fabricated in polysiloxane/BN nanosheet composite film under a high DC electric field. The hexagonal BN nanosheets were dispersed by sonication in a prepolymer mixture of polysiloxane followed by a high-speed mixing. The homogeneous suspension was cast on a spacer of microscale thickness and applied to a high DC electric field before it became cross-linked. X-ray diffraction, scanning electron microscopy, and digital microscopy revealed that LABNs formed in the polysiloxane matrix and that the BN nanosheets in the LABNs were aligned perpendicular to the film plane with high anisotropy. This is the first time that linear assemblies of nanosheets have been fabricated in an organic-inorganic hybrid film by applying a DC electric field. The enhanced thermal conductivity of the composite film is attributed to the LABNs. The LABN formation and heat conduction mechanisms are discussed. The polysiloxane/BN nanosheet composite film has the potential to be used semiconductor applications that require both a high thermal conductivity and a high electric insulation.

Electrokinetic Instability Flow in Nanofilm-Coated Microfluidic Channels

2009 ◽  
Vol 60-61 ◽  
pp. 330-333
Author(s):  
Wei Chih Chen ◽  
Ting Fu Hong ◽  
Wen Bo Luo ◽  
Chang Hsien Tai ◽  
Chien Hsiung Tsai ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Flow Instability ◽  
Microfluidic Channels ◽  
Conductivity Ratio ◽  
Electrokinetic Instability ◽  
Two Samples ◽  
Significant Difference

This paper presented a parametric experimental study of electrokinetic instability phenomena in a cross-shaped configuration microfluidic device with varying channel depths and conductivity ratios. The flow instability is observed when applied electric field strength exceeds a certain critical value. The critical electric field strength is examined as a function of the conductivity ratio of two samples liquid, microchannel depth, and the treatment of microchannel wetted surface. It is found that the critical electric field strengths for the onset of electrokinetic instability are strongly dependent on the conductivity ratio of two samples liquid, and decrease as the channel depths increasing of microfluidic devices. In the present study, the surface inside microchannels is treated utilizing hydrophilic and hydrophobic organic-based SOG (spin-on-glass) nanofilms for glass-based microchips. The experimental results indicate that no significant difference for the critical electric fields for the onset of electrokinetic instability phenomena in both hydrophilic and hydrophobic SOG coating in the surface of microchannels. The critical electric fields for the onset of electrokinetic instability phenomena are slightly lower in both SOG coated cases in compare with that of the non-coated microchannel.

Joule Heating Induced Heat Transfer and Its Effects on Electrokinetic Mixing in T-Shape Microfluidic Channels

2007 ◽  
Author(s):  
Gongyue Tang ◽  
Chun Yang ◽  
Yee Cheong Lam
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Numerical Simulations ◽  
Joule Heating ◽  
Solution Temperature ◽  
Microfluidic Channels ◽  
Governing Equations ◽  
Electrokinetic Flow ◽  
Layer Potential ◽  
Temperature Distributions

In this paper, we report numerical and experimental studies of the Joule heating-induced heat transfer in fabricated T-shape microfluidic channels. We have developed comprehensive 3D mathematical models describing the temperature development due to Joule heating and its effects on electrokinetic flow. The models consist of a set of governing equations including the Poisson-Boltzmann equation for the electric double layer potential profiles, the Laplace equation for the applied electric field, the modified Navier-Stokes equations for the electrokinetic flow field, and the energy equations for the Joule heating induced conjugated temperature distributions in both the liquid and the channel walls. Specifically, the Joule number is introduced to characterize Joule heating, to account for the effects of the electric field strength, electrolyte concentration, channel dimension, and heat transfer coefficient outside channel surface. As the thermophysical and electrical properties including the liquid dielectric constant, viscosity and electric conductivity are temperature-dependent, these governing equations are strongly coupled. We therefore have used the finite volume based CFD method to numerically solve the coupled governing equations. The numerical simulations show that the Joule heating effect is more significant for the microfluidic system with a larger Joule number and/or a lower thermal conductivity of substrates. It is found that the presence of Joule heating makes the electroosmotic flow deviate from its normal “plug-like” profiles, and cause different mixing characteristics. The T-shape microfluidic channels were fabricated using rapid prototyping techniques, including the Photolithography technique for the master fabrication and the Soft Lithography technique for the channel replication. A rhodamine B based thermometry technique, was used for direct “in-channel” measurements of liquid solution temperature distributions in microfluidic channels, fabricated by the PDMS/PDMS and Glass/PDMS substrates. The experimental results were compared with the numerical simulations, and reasonable agreement was found.

scholarly journals Influence of Surface-conductivity Nonuniformity on Charge Accumulation Phenomena of GIS Insulator under DC Electric Field

2011 ◽  
Vol 131 (7) ◽  
pp. 584-590 ◽  
Author(s):  
Taiki Donen ◽  
Hiroyuki Iwabuchi ◽  
Shigeyasu Matsuoka ◽  
Akiko Kumada ◽  
Kunihiko Hidaka ◽  
...  
Keyword(s):  
Electric Field ◽  
Surface Conductivity ◽  
Charge Accumulation ◽  
Dc Electric Field

JOULE HEATING INDUCED HEAT TRANSFER IN ELECTROKINETIC FLOW THROUGH MICROFLUIDIC CHANNELS

Equipment ◽  
2006 ◽  
Author(s):  
C. Yang ◽  
G. Y. Tang ◽  
D. G. Yan ◽  
H. Q. Gong ◽  
John C. Chai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Joule Heating ◽  
Microfluidic Channels ◽  
Electrokinetic Flow ◽  
Flow Through
Sign in / Sign up

Export Citation Format

Share Document