Geometry Effect on the Electrokinetic Instability of the Electroosmotic Flow in Microfluidic Channels

2008 ◽  
Author(s):  
Yee Cheong Lam ◽  
Gongyue Tang ◽  
Deguang Yan
Keyword(s):  
Threshold Voltage ◽  
Electroosmotic Flow ◽  
Fluorescent Imaging ◽  
Microfluidic Channels ◽  
Channel Geometry ◽  
Electrolyte Conductivity ◽  
Electrokinetic Instability ◽  
Micro Channels ◽  
Onset Voltage ◽  
Abrupt Contraction

To study the effect of geometry on electroosmotic flow in micro channels, we fabricated PDMS-glass microchannels of different designs, which have patterned channels with abrupt contraction of different sizes. Using fluorescent imaging technology, we demonstrated the effect of geometry on the instability of DC driven electroosmotic flow in microfluidic channels. For certain geometry and conductivity of the electrolyte solution (Sodium Bicarbonate), there is a threshold voltage for electroosmotic instability, exhibiting itself as “ripple”. Generally, the factors which affect the threshold voltage include channel width, channel geometry, and electrolyte conductivity. Narrower channel resulted in higher onset voltage. As conductivity of the electrolyte increases, the threshold voltage tends to increase. Early transition to unstable electroosmotic flow in microfluidic channels was observed under relatively low Re.

Solute Dispersion by Electroosmotic flow in Nonuniform Microfluidic Channels

2001 ◽  
pp. 615-616 ◽  
Author(s):  
M. T. Blom ◽  
E. F. Hasselbrink ◽  
H. Wensink ◽  
A. van den Berg
Keyword(s):  
Electroosmotic Flow ◽  
Microfluidic Channels ◽  
Solute Dispersion

scholarly journals Optimization of selective laser-induced etching (SLE) for fabrication of 3D glass microfluidic device with multi-layer micro channels

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Sungil Kim ◽  
Jeongtae Kim ◽  
Yeun-Ho Joung ◽  
Sanghoon Ahn ◽  
Jiyeon Choi ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Microfluidic Channel ◽  
Design Guidelines ◽  
Process Window ◽  
Microfluidic Channels ◽  
Micro Channels ◽  
Scan Speed ◽  
Energy Pulse ◽  
Laser Induced Etching ◽  
Etching Selectivity

Abstract We present the selective laser-induced etching (SLE) process and design guidelines for the fabrication of three-dimensional (3D) microfluidic channels in a glass. The SLE process consisting of laser direct patterning and wet chemical etching uses different etch rates between the laser modified area and the unmodified area. The etch selectivity is an important factor for the processing speed and the fabrication resolution of the 3D structures. In order to obtain the maximum etching selectivity, we investigated the process window of the SLE process: the laser pulse energy, pulse repetition rate, and scan speed. When using potassium hydroxide (KOH) as a wet etchant, the maximum etch rate of the laser-modified glass was obtained to be 166 μm/h, exhibiting the highest selectivity about 333 respect to the pristine glass. Based on the optimized process window, a 3D microfluidic channel branching to three multilayered channels was successfully fabricated in a 4 mm-thick glass. In addition, appropriate design guidelines for preventing cracks in a glass and calibrating the position of the dimension of the hollow channels were studied.

Lower Entropy Generation in Microchannels With Laminar Single Phase Flow

2010 ◽  
Author(s):  
E. Galvis ◽  
J. R. Culham
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Entropy Generation ◽  
Entropy Generation Rate ◽  
Channel Geometry ◽  
Micro Channels ◽  
Optimum Channel

In this study the entropy generation minimization method is used to find the optimum channel dimensions in micro heat exchangers with a uniform heat flux. With this approach, pressure drop and heat transfer in the micro channels are considered simultaneously during the optimization analysis. A computational model is developed to find the optimum channel depth knowing other channel geometry dimensions and coolant inlet properties. The flow is assumed laminar and both hydrodynamically and thermally fully developed and incompressible. However, to take into account the effect of the developing length in the friction losses, the Hagenbach’s factor is introduced. The micro channels are assumed to have an isothermal or isoflux boundary condition, non-slip flow, and fluid properties have dependency on temperature accordingly. For these particular case studies, the pressure drop and heat transfer coefficient for the isoflux boundary condition is higher than the isothermal case. Higher heat transfer coefficient and pressure drop were found when the channel size decreased. The optimum channel geometry that minimizes the entropy generation rate tends to be a deep, narrow channel.

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.

scholarly journals Design and simulation of microfluidic smart bandage using Comsol Multiphysics

2021 ◽  
Vol 12 (5) ◽  
pp. 1650-1662
Author(s):  
Priti Rajput, Et. al.
Keyword(s):  
Human Body ◽  
Drug Testing ◽  
Herbal Medicines ◽  
Drug Distribution ◽  
Outer Radius ◽  
The Body ◽  
Microfluidic Channels ◽  
Body Parts ◽  
Capillary Action ◽  
Micro Channels

Microfluidics is an emerging field finding its applications in biomedical engineering for investigations of cellular micro structures. Human body is composed of 70% of water having thin and fine structure of microfluidic blood channels spread throughout the body. These microchannels supply essential nutrients to each part of the body at right time and in right amount. Microfluidics is the science of controlling and manipulating the fluid in micro channels. Manipulating the flow through the microchannels is useful for developing electronic devices, artificial human body parts, and economical diagnostics tools. Microfluidics also helps in manufacturing of pharmaceuticals and carrying out precise chemical analysis of complex systems. A number of diagnostic devices and artificial human organs like lungs, heart, kidneys, etc. have been simulated using microfluidics for developing easy, economical, non-invasive, and rapid method of drug testing. Recently, its applications have also been investigated in smart bandage design. Further, blend of microfluidics with herbal medicines is expected to enhance the healing along with negligible side effects unlike allopathic treatments. The scope of the present research is to develop a smart bandage capable of sensing the status of the wound and supplying required amount of drugs using microfluidic channels. The flow rate of drugs through microchannels is simulated using the physics of laminar flow, capillary action, and diffusion phenomena for optimizing the size and shape of the constituent components of the bandage like microfluidic channels, mixers, and porous material used for drug distribution with in the active area of the bandage. The analysis of the results shows that the mixer having inner radius as 150 microns and outer radius as 250 microns is sufficient to mix the incoming drugs via inlets of 50 microns’ diameter. Results also show that capillary action dominates the diffusion phenomenon for supplying the drugs to the wound. The investigations of the prototype show that a smart bandage having the provisions of uniform drug distribution, automatic control, on board pH, moisture, O2 measurement, and dc current based healing mechanism is possible to be incorporated with in a comfortable size for fast wound healing.

scholarly journals The Effects Of Blast Lag In Abrasive Jet Machined Micro-Channel Intersections

2021 ◽  
Author(s):  
Soheil Shafagh
Keyword(s):  
Abrasive Particle ◽  
Substrate Material ◽  
Solid Particles ◽  
Microfluidic Channels ◽  
Channel Networks ◽  
Cross Sectional ◽  
Surface Evolution ◽  
Developed Surface ◽  
Micro Channels ◽  
Micro Machine

Abrasive jet micro-machining (AJM) uses compressed air carrying abrasive solid particles to micro-machine a variety of features into surfaces. If the features are smaller than a few mm, then a patterned erosion-resistant mask is used to protect the substrate material, leaving exposed areas to define the features. Previous investigations have revealed a ‘blast lag’ phenomenon in which, for the same dose of abrasive particles, the etched depth of micro-channels and holes tends to decrease as the features become narrower. Blast lag occurs when using AJM on brittle substrates because of the natural tendency to rapidly form a V-shaped cross-sectional profile which inhibits abrasive particle strikes on the narrow vertex at the feature centerline. In this thesis, for the first time, the blast lag phenomenon is studied when using AJM to machine a network of microfluidic channels. It is found that, in some cases, differences in blast lag occurring at channel intersections and within the channels themselves, can lead to channel networks of non-uniform depth. A previously developed surface evolution model is used to predict the onset of blast lag in the channels and intersections, and thus explain these differences. Finally, methods to eliminate the differences are discussed.

scholarly journals S056024 Flow Properties of Several Solutions in Micro-Channels with Abrupt Contraction

2011 ◽  
Vol 2011 (0) ◽  
pp. _S056024-1-_S056024-3
Author(s):  
Hiroshige UCHIYAMA ◽  
Takatsune NARUMI ◽  
Tomiichi HASEGAWA ◽  
Akiomi USHIDA ◽  
Ryuichi KAYABA
Keyword(s):  
Flow Properties ◽  
Micro Channels ◽  
Abrupt Contraction

scholarly journals Effect of Joule Heating on Cell Viability and Device Reliability

2021 ◽  
Author(s):  
Mohamed Yousuff Caffiyar ◽  
Kashif Irshad ◽  
Vineet Tirth ◽  
Mohamed Zackria Ansar B.I ◽  
Ali Algahtani ◽  
...  
Keyword(s):  
Microfluidic Device ◽  
Joule Heating ◽  
Threshold Value ◽  
Cell Loss ◽  
Cell Types ◽  
Microfluidic Channels ◽  
Biological Entity ◽  
Heating Effects ◽  
Device Reliability ◽  
Micro Channels

The application of electrode-based microfluidic devices in biological entity often imposes a problem due to joule heating. The strong applied potentials or micro channels having narrow cross sections generate undesirable temperature inside the microfluidic channels leading to strong thermal distribution inside the micro channel. When intrinsic distribution of temperature, if not fix with threshold value, causes device damage or cell loss. In this work, we investigate the effects of temperature generated due to joules heating effects and we attempt to address the design constraints for minimizing the joule heating effects in the microfluidic device for developing effective microfluidic device. The device reliability was analyzed under different parametric constraints for various types of substrate materials (PDMS, PMMA, Polyimide and glass). We also attempt to investigate the effects of cell reliability due to strong temperature gradients generated through different applied potentials on different cell types. Furthermore, the response of the device performance due to different electrode configuration and different conductivity of the medium was also studied. Our investigation will eventually provide guidelines for microfluidic researchers to fabricate efficient electrode based microfluidic device which will ultimately help to choose a critical channel dimensions, threshold potentials, and conductivity of solutions in order to avoid device damage and cell loss.

Effects of Contraction Ratio on Elastic Instability of Hyaluronate Solution in a Micro Channel

2015 ◽  
Author(s):  
Taiki Oka ◽  
Ruri Hidema ◽  
Hiroshi Suzuki ◽  
Yoshiyuki Komoda
Keyword(s):  
Water Solution ◽  
Flow Behavior ◽  
Sodium Hyaluronate ◽  
Flow Characteristics ◽  
Micro Channel ◽  
Elastic Instability ◽  
Channel Geometry ◽  
Contraction Ratio ◽  
Abrupt Contraction ◽  
Phosphate Buffered Saline

Flow behaviors of sodium hyaluronate (HA-Na) in water solution and in phosphate buffered saline (PBS) solution as a viscoelastic fluids in planer abrupt contraction-expansion channels has been observed in this study. Especially, the effect of the geometry of the flow path on the flow behavior was focused on. The corner vortices in the corner of the upper region in the abrupt contraction-expansion channels were also analyzed to quantify the flow characteristics. The elasticity numbers of the solution, which is affected by rheological properties of the solution and the channel geometry had a big influence on the fluidity, that is, stable or unstable, when the concentration of the solution in lower. It was concluded that such stable and unstable flows are categorized on Wissenberg-Reynolds number space.

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