scholarly journals Shrinking microbubbles with microfluidics: mathematical modelling to control microbubble sizes

2021 ◽  
Author(s):  
A. Salari ◽  
V. Gnyawali ◽  
I. M. Griffiths ◽  
R. Karshafian ◽  
Michael C. Kolios ◽  
...  
Keyword(s):  
Life Sciences ◽  
Microfluidic Channel ◽  
Flow Focusing ◽  
Bubble Generation ◽  
Microfluidic Platform ◽  
Interfacial Tensions ◽  
Precise Control ◽  
Ultrasound Diagnostics ◽  
Bubble Sizes ◽  
Good Agreement

Microbubbles have applications in industry and life-sciences. In medicine, small encapsulated bubbles (< 10 μm) are desirable because of their utility in drug/oxygen delivery, sonoporation, and ultrasound diagnostics. While there are various techniques for generating microbubbles, microfluidic methods are distinguished due to their precise control and ease-offabrication. Nevertheless, sub-10 μm diameter bubble generation using microfluidics remains challenging, and typically requires expensive equipment and cumbersome setups. Recently, our group reported a microfluidic platform that shrinks microbubbles to sub-10 μm diameters. The microfluidic platform utilizes a simple microbubble-generating flow-focusing geometry, integrated with a vacuum shrinkage system, to achieve microbubble sizes that are desirable in medicine, and pave the way to eventual clinical uptake of microfluidically generated microbubbles. A theoretical framework is now needed to relate the size of the microbubbles produced and the system’s input parameters. In this manuscript, we characterize microbubbles made with various lipid concentrations flowing in solutions that have different interfacial tensions, and monitor the changes in bubble size along the microfluidic channel under various vacuum pressures. We use the physics governing the shrinkage mechanism to develop a mathematical model that predicts the resulting bubble sizes and elucidates the dominant parameters controlling bubble sizes. The model shows a good agreement with the experimental data, predicting the resulting microbubble sizes under different experimental input conditions. We anticipate that the model will find utility in enabling users of the microfluidic platform to engineer bubbles of specific sizes.

scholarly journals Shrinking microbubbles with microfluidics: mathematical modelling to control microbubble sizes

2021 ◽  
Author(s):  
A. Salari ◽  
V. Gnyawali ◽  
I. M. Griffiths ◽  
R. Karshafian ◽  
Michael C. Kolios ◽  
...  
Keyword(s):  
Life Sciences ◽  
Microfluidic Channel ◽  
Flow Focusing ◽  
Bubble Generation ◽  
Microfluidic Platform ◽  
Interfacial Tensions ◽  
Precise Control ◽  
Ultrasound Diagnostics ◽  
Bubble Sizes ◽  
Good Agreement

Microbubbles have applications in industry and life-sciences. In medicine, small encapsulated bubbles (< 10 μm) are desirable because of their utility in drug/oxygen delivery, sonoporation, and ultrasound diagnostics. While there are various techniques for generating microbubbles, microfluidic methods are distinguished due to their precise control and ease-offabrication. Nevertheless, sub-10 μm diameter bubble generation using microfluidics remains challenging, and typically requires expensive equipment and cumbersome setups. Recently, our group reported a microfluidic platform that shrinks microbubbles to sub-10 μm diameters. The microfluidic platform utilizes a simple microbubble-generating flow-focusing geometry, integrated with a vacuum shrinkage system, to achieve microbubble sizes that are desirable in medicine, and pave the way to eventual clinical uptake of microfluidically generated microbubbles. A theoretical framework is now needed to relate the size of the microbubbles produced and the system’s input parameters. In this manuscript, we characterize microbubbles made with various lipid concentrations flowing in solutions that have different interfacial tensions, and monitor the changes in bubble size along the microfluidic channel under various vacuum pressures. We use the physics governing the shrinkage mechanism to develop a mathematical model that predicts the resulting bubble sizes and elucidates the dominant parameters controlling bubble sizes. The model shows a good agreement with the experimental data, predicting the resulting microbubble sizes under different experimental input conditions. We anticipate that the model will find utility in enabling users of the microfluidic platform to engineer bubbles of specific sizes.

scholarly journals Numerical and Experimental Study on the Internal Flow of the Venturi Injector

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 64 ◽  
Author(s):  
Hao Li ◽  
Hong Li ◽  
Xiuqiao Huang ◽  
Qibiao Han ◽  
Ye Yuan ◽  
...  
Keyword(s):  
Energy Loss ◽  
Internal Flow ◽  
Hydraulic Performance ◽  
Mixing Process ◽  
Cavitation Model ◽  
Precise Control ◽  
Mixing Chamber ◽  
Numerical Simulation Methods ◽  
The Stability ◽  
Good Agreement

To study the appropriate numerical simulation methods for venturi injectors, including the investigation of the hydraulic performance, mixing process, and the flowing law of the two internal fluids, simulations and experiments were conducted in this study. In the simulations part, the cavitation model based on the standard k–ε turbulence and mixture models was added, after convergence of the calculations. The results revealed that the cavitation model has good agreement with the experiment. However, huge deviations occurred between the experimental results and the ones from the calculation when not considering the cavitation model after cavitation. Thus, it is inferred that the cavitation model can exactly predict the hydraulic performance of a venturi injector. In addition, the cavitation is a crucial factor affecting the hydraulic performance of a venturi injector. The cavitation can ensure the stability of the fertilizer absorption of the venturi injector and can realize the precise control of fertilization by the venturi injector, although it affects the flow stability and causes energy loss. Moreover, this study found that the mixing chamber and throat are the main areas of energy loss. Furthermore, we observed that the internal flow of the venturi injector results in the majority of mixing taking place at the diffusion and outlet sections.

scholarly journals High-resolution sampling of beam-driven plasma wakefields

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Schröder ◽  
C. A. Lindstrøm ◽  
S. Bohlen ◽  
G. Boyle ◽  
R. D’Arcy ◽  
...  
Keyword(s):  
Electric Fields ◽  
High Energy ◽  
Acceleration Process ◽  
Plasma Parameters ◽  
Particle Beams ◽  
Particle In Cell ◽  
Precise Control ◽  
Plasma Wakefield Accelerators ◽  
Plasma Wakefield ◽  
Good Agreement

AbstractPlasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities. Such applications require particle beams with a well-controlled energy spectrum, which necessitates detailed tailoring of the plasma wakefield. Precise measurements of the effective wakefield structure are therefore essential for optimising the acceleration process. Here we propose and demonstrate such a measurement technique that enables femtosecond-level (15 fs) sampling of longitudinal electric fields of order gigavolts-per-meter (0.8 GV m−1). This method—based on energy collimation of the incoming bunch—made it possible to investigate the effect of beam and plasma parameters on the beam-loaded longitudinally integrated plasma wakefield, showing good agreement with particle-in-cell simulations. These results open the door to high-quality operation of future plasma accelerators through precise control of the acceleration process.

scholarly journals Three step flow focusing enables image-based discrimination and sorting of late stage 1 Haematococcus pluvialis cells

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0249192
Author(s):  
Daniel Kraus ◽  
Andreas Kleiber ◽  
Enrico Ehrhardt ◽  
Matthias Leifheit ◽  
Peter Horbert ◽  
...  
Keyword(s):  
Late Stage ◽  
Haematococcus Pluvialis ◽  
Lateral Displacement ◽  
Microfluidic Channel ◽  
Image Features ◽  
Target Cells ◽  
Flow Focusing ◽  
Step Flow ◽  
Stage 1 ◽  
Mixed Stage

Label-free and gentle separation of cell stages with desired target properties from mixed stage populations are a major research task in modern biotechnological cultivation process and optimization of micro algae. The reported microfluidic sorter system (MSS) allows the subsequent investigation of separated subpopulations. The implementation of a viability preserving MSS is shown for separation of late stage 1 Haematococcus pluvialis (HP) cells form a mixed stage population. The MSS combines a three-step flow focusing unit for aligning the cells in single file transportation mode at the center of the microfluidic channel with a pure hydrodynamic sorter structure for cell sorting. Lateral displacement of the cells into one of the two outlet channels is generated by piezo-actuated pump chambers. In-line decision making for sorting is based on a user-definable set of image features and properties. The reported MSS significantly increased the purity of target cells in the sorted population (94%) in comparison to the initial mixed stage population (19%).

Simulation and Experimental Research for Microparticles in Microchannels With Dielectrophoretic Field-Flow Fractionation

2010 ◽  
Author(s):  
Minghao Song ◽  
Hongwei Sun
Keyword(s):  
Microfluidic Channel ◽  
Biological Molecules ◽  
Spherical Particles ◽  
Uniform Electric Field ◽  
Field Flow Fractionation ◽  
Particle Movement ◽  
Moment Theory ◽  
Particle Hydrodynamics ◽  
Flow Fractionation ◽  
Good Agreement

The Dielectrophoretic Field-flow Fractionation (DEP-FFF) is a very promising separation technique for particles and biological molecules. To further explore this technology, we conducted a computational and experimental investigation of a single particle movement in a PDMS microfluidic channel under DEP force, where both electrokinetic effects and particle hydrodynamics are considered. The model was first validated with dipole moment theory, and a polystyrene particle (∼10 μm) behavior in a non-uniform electric field created by a pair of non-symmetrical electrodes was then studied numerically. The simulation results were compared with experimental results and a good agreement was obtained. Further research is underway to study the behavior of non-spherical particles (such as nanowire, nanorod, and nanofiber) in other microfluidic systems.

Impedance spectroscopy-based cell/particle position detection in microfluidic systems

Lab on a Chip ◽  
2017 ◽  
Vol 17 (7) ◽  
pp. 1264-1269 ◽  
Author(s):  
H. Wang ◽  
N. Sobahi ◽  
A. Han
Keyword(s):  
Impedance Spectroscopy ◽  
High Throughput ◽  
Low Cost ◽  
Microfluidic Channel ◽  
Microfluidic Systems ◽  
Microfluidic Platform ◽  
Particle Position ◽  
Position Detection

A high-throughput and low-cost impedance spectroscopy-based microfluidic platform capable of detecting/discriminating the transverse positions of cells/particles flowing within a microfluidic channel.

Enhanced Electroluminescence of CdSe/ZnS Quantum Dot Light–emitting Diodes with Phosphorescent Donors

2011 ◽  
Vol 1348 ◽  
Author(s):  
Yiqiang Zhang ◽  
X. A. Cao
Keyword(s):  
Energy Transfer ◽  
Light Emitting Diodes ◽  
Organic Dyes ◽  
Effective Means ◽  
Organic Light Emitting Diodes ◽  
Exciton Energy ◽  
Light Emitting ◽  
Precise Control ◽  
Organic Light ◽  
Good Agreement

ABSTRACTWe demonstrated the enhancement of electroluminescence (EL) from green CdSe/ZnS QDs in hybrid QD/organic light-emitting diodes (QD-LEDs) by employing blue phosphorescent dyes Bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium (FIrpic) as efficient exciton harvesters and energy transfer donors. Precise control of the concentration of the FIrpic donors doped in a 4,4’-N, N’-dicarbazole-biphenyl (CBP) host and their distance from the QD layer led to complete triplet exciton energy transfer and EL enhancement by a factor of 2.5. The Förster distance between FIrpic molecules and green CdSe/ZnS QDs was determined to be ∼ 8 nm, which is in a good agreement with the value calculated using the Förster model. Our study shows that integrating colloidal QDs with phosphorescent organic dyes provides an effective means for improving the quantum efficiency of QD-based hybrid LEDs.

scholarly journals On the breakup of an air bubble injected into a fully developed turbulent flow. Part 1. Breakup frequency

1999 ◽  
Vol 401 ◽  
pp. 157-182 ◽  
Author(s):  
C. MARTÍNEZ-BAZÁN ◽  
J. L. MONTAÑÉS ◽  
J. C. LASHERAS
Keyword(s):  
Bubble Size ◽  
Critical Diameter ◽  
Air Bubble ◽  
Wide Range ◽  
Fully Developed Turbulent Flow ◽  
Flow Part ◽  
Bubble Sizes ◽  
Rate Of Dissipation ◽  
Processing Techniques ◽  
Good Agreement

The transient evolution of the bubble-size probability density functions resulting from the breakup of an air bubble injected into a fully developed turbulent water ow has been measured experimentally using phase Doppler particle sizing (PDPA) and image processing techniques. These measurements were used to determine the breakup frequency of the bubbles as a function of their size and of the critical diameter Dc defined as Dc = 1.26 (σ/ρ)3/5ε−2/5, where ε is the rate of dissipation per unit mass and per unit time of the underlying turbulence. A phenomenological model is proposed showing the existence of two distinct bubble size regimes. For bubbles of sizes comparable to Dc, the breakup frequency is shown to increase as (σ/ρ)−2/5ε−3/5 √D/Dc−1, while for large bubbles whose sizes are greater than 1.63Dc, it decreases with the bubble size as ε1/3D−2/3. The model is shown to be in good agreement with measurements performed over a wide range of bubble sizes and turbulence intensities.

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