This book reviews the latest advancement of microfluidics and nanofluidics with a focus on electrokinetic phenomena in microfluidics and nanofluidics. It provides fundamental understanding of several new interfacial electrokinetic phenomena in microfluidics and nanofluidics. Chapter 1 gives a brief review of the fundamentals of interfacial electrokinetics. Chapter 2 shows induced charge electrokinetic transport phenomena. Chapter 3 presents the new advancement in DC dielectrophoresis. Chapter 4 introduces a novel nanofabrication method and the systematic studies of electrokinetic nanofluidics. Chapter 5 presents electrokinetic phenomena associated with Janus particles and Janus droplets. Chapter 6 introduces a new direction of electrokinetic nanofluidics: nanofluidic iontronics. Chapter 7 discusses an important differential resistive pulse sensor in microfluidics and nanofluidics.
Author(s): Dongqing Li
Series: Fluid Mechanics and Its Applications, 133
Publisher: Springer
Year: 2022
Language: English
Pages: 287
City: Cham
Preface
Contents
About the Author
1 Basics of Interfacial Electrokinetics
1.1 Electrical Double Layer
1.1.1 Electrical Field in a Dielectric Medium
1.1.2 Origin of Surface Charge
1.1.3 Electrical Double Layer (EDL)
1.1.4 Boltzmann Distribution
1.1.5 Theoretical Model and Analysis of EDL
1.1.6 EDL Field Near a Flat Surface
1.1.7 EDL Field Around a Spherical Surface
1.1.8 EDL Field Around a Cylinder
1.1.9 Concentration and pH Dependence of Surface Charge and Zeta Potential
1.2 Electroosmotic Flows in Microchannels
1.2.1 Electroosmotic Flow Velocity
1.2.2 Electroosmotic Flow in a Slit Microchannel
1.2.3 Electroosmotic Flow in a Cylindrical Microchannel
1.3 Introduction to Electrophoresis
References
2 Induced Charge Electrokinetic Transport Phenomena
2.1 Basics of Induced Charge Electrokinetics
2.2 Induced Charge Electroosmotic Flow [3, 4, 8, 9, 10, 11]
2.2.1 Flow Field with Vortices in the Converging–Diverging Section
2.2.2 Regulating Flow
2.3 Flow Mixing by Induced Charge Electroosmotic Flow
2.4 Induced Charge Electrokinetic Motion of Fully Polarizable Particles
2.4.1 Electric Field
2.4.2 Flow Field
2.4.3 Particle Motion
2.4.4 Transient Motion of Conducting Particles Along the Center of a Microchannel
2.4.5 Wall Effects on Induced Charge Electrokinetic Motion of Conducting Particles
2.4.6 Particle Focusing in a Microchannel
2.4.7 Particle Separation by Density
2.5 Induced Charge Particle–Particle Interactions
2.6 Polarizability Dependence of Electrokinetic Motion of Dielectric Particles
2.6.1 Polarization of Dielectrics
2.6.2 The Induced Surface Potential and Electroosmotic Flow
2.6.3 Interaction of Two Dielectric Particles Due to Induced Charge EOF
References
3 DC-Dielectrophoresis in Microfluidic Chips
3.1 Basics of Dielectrophoresis
3.2 DC-DEP Separation of Micro-particles and Cells
3.3 DEP Produced by Asymmetric Orifices on Sidewalls of Microchannel
3.3.1 DC-DEP Separation of Micro-particles By Size
3.3.2 DC-DEP Separation of Nano-particles By Size
3.3.3 DC-DEP Separation of Nano-particles By Type
3.3.4 AC-DEP Separation of Biological Cells
References
4 Electroosmotic Flow and Electrophoresis in Nanochannels
4.1 Difference and Challenge
4.2 Single Nanochannel Fabrication by Nano-crack Method
4.2.1 Effect of Reagents
4.2.2 Effects of Alcohol Volume and Heating Time
4.2.3 Concentration Effects and the Role of Water
4.2.4 Temperature Effects
4.2.5 Number of Nano-cracks
4.2.6 Controlling the Locations of the Nano-cracks
4.2.7 How to Transfer the Pattern of a Nano-crack into a Positive Nanochannel Mold
4.2.8 Effects of Photoresist Type (Solvent Content)
4.2.9 Effects of Spin-Coating Time
4.2.10 Effects of UV Exposure Dose
4.2.11 Thickness of the Photoresist Layer
4.2.12 Bi-layer PDMS Microchannel and Nanochannel Fabrication
4.2.13 Durability of Nanochannel Molds
4.2.14 Chip Bonding
4.3 Characteristics of Electroosmotic Flow in Nanochannels
4.3.1 EOF Velocity Measurement by the Current Slope Method
4.3.2 Channel Size Effects
4.3.3 Ionic Concentration Effects
4.3.4 Electric Field Effect
4.3.5 Ion Size Effects
4.3.6 Ion Valence Effects
4.3.7 pH Value Effects
4.4 Nanoparticle Transport in Nanochannels
4.4.1 Ionic Concentration Effects
4.4.2 Effects of Particle Size to Channel Size Ratio
4.4.3 Electric Field Effects
References
5 Janus Particles and Janus Droplets
5.1 Introduction
5.2 Induced Charge Electrokinetic Motion of Janus Particles
5.2.1 Electric Field
5.2.2 Flow Field
5.2.3 Particle Motion
5.2.4 Micro-vortex Generation and Particle Motion
5.2.5 Electrokinetic Motion of Janus Particle in Different Orientations
5.2.6 Zeta Potential Effect on Vortices Around Janus Particle
5.2.7 Effect of Janus Particle Size on Its Motion
5.2.8 Different Portion of Polarizable Material of Janus Particle
5.2.9 Experimentally Observed Motion of Janus Particles
5.3 Electrically Induced Janus Droplets
5.3.1 Effect of the Concentration of the Nanoparticle Suspension
5.3.2 Effect of the Applied Electric Field
5.3.3 Vortices Around EIJD
5.3.4 Effect of the Applied Electrical Field
5.3.5 Effect of the Surface Coverage Under the Same Electrical Field
5.4 Electrokinetic Motion of EIJD in Microchannels
5.4.1 Formation of EIJD with Different Surface Coverage by Nanoparticles (r)
5.4.2 Vortices in Vicinity of Janus Droplet
5.4.3 Effects of Applied Electrical Field and Surface Coverage of Nanoparticles on Electrokineitc Motion
5.4.4 Effect of the Janus Droplet Size on Electrokineitc Motion
5.4.5 Effect of Electrolyte Concentration on Electrokineitc Motion of EIJD
5.4.6 Flow Focusing with Positively Charged Droplets
5.5 Droplets with Multiple Heterogeneous Surface Strips
5.5.1 EOF Fields Around Janus Droplets
5.5.2 Electrokinetic Motion of Droplets with Different Nanoparticle Films
5.6 Micro-valve Controlled by an Electrically Induced Janus Droplet
5.6.1 Rotation of the EIJD by Switching Electric Field
5.6.2 Operation of the Micro-valve
5.6.3 Effect of the Electric Field Strength on Micro-valve Switching Time
5.6.4 Sealing Performance of the EIJD Micro-valve
References
6 Nanofluidic Iontronic Devices
6.1 Nanofluidic Based Iontronics
6.2 Ionic Diode Based on an Asymmetric-Shaped Nanoparticle Membrane
6.2.1 Fabrication of Asymmetric NCNM
6.2.2 Fabrication of Nanofluidic Chips
6.2.3 Measurement System and Experimental Procedures
6.2.4 Characterization of the Asymmetric NCNM Membrane
6.2.5 Mechanism of the Ionic Current Rectification
6.2.6 Performance Evaluation of the NCNM Ionic Diode
6.2.7 Modification of the NCNM Ionic Diode with Cationic Surfactant
6.2.8 NCNM Ionic Transistor
6.2.9 Ionic Diode Bridge
6.3 Surface Modification Using Layer-by-Layer Method—Change of Channel Size and Surface Charge
6.3.1 Surface Modification Using LBL Method
6.3.2 Growth of Polymer Layers on Flat Hard-PDMS Surfaces [2, 3]
6.3.3 Growth of Polymer Layers in Nanochannels [2, 3]
6.3.4 Ion Type Effects
6.4 Single Nanochannel Ionic Diode—Regulation of Ion Transport in Nanofluidics by Surface Modification
6.4.1 Surface Modification of Nanochannel for Nanofluidic Diode
6.4.2 Working Principle of the Nanofluidic Diode
6.4.3 Effects of Frequency of the Applied Electric Field
6.4.4 Effects of the Ionic Concentration
6.4.5 Effects of Nanochannel Length
6.4.6 Effects of Electric Field Strength
6.5 From Ionic Diode to Ionic Transistor and Ionic Circuit [4]
6.5.1 Ionic Bipolar Junction Transistor
6.5.2 Full-Wave Ionic Rectifier
References
7 Differential Resistive Pulse Sensor
7.1 Resistive Pulse Sensor
7.2 Microfluidic Differential Resistive Pulse Sensor
7.2.1 Effects of Particle-to-Sensing Gate Volume Ratio
7.2.2 Applied Voltage Effects
7.3 Improved Sensitivity by Electrokinetic Flow Focusing Method
7.4 High-Throughput Microfluidic Differential Resistive Pulse Sensor
7.5 Resistive Pulse Sensor with a Nanochannel Sensing Gate
7.6 Enhanced Sensitivity by Modifying Surface Charge of Nano Sensing Gate
7.7 Resistive Pulse Sensor with a Carbon Nanotube as Sensing Gate
7.7.1 Detection of Potassium Ions
7.7.2 Detection of 30-nt and 15-nt ssDNAs
References
