Flow, focused hydrodynamic focusing

Malvern Sysmex SD-2000 particle counter and sizer delivers high-performance particle size analysis from 1 to 120 pm by combining electrozone sensing with hydrodynamic sheath flow focusing. 

Flow cytometers distribute suspensions of cells into a single column by laminar flow and hydrodynamic focusing. Individual cells are then intercepted by a laser source, and the scattered light and fluorescence emission (when using... 

There are three basic requirements of a separation colunm for cIEF zero or substantially reduced electroosmotic flow (EOF), hydrodynamic flow, and interaction between protein samples and the column wall. Columns used in cIEF are usually coated on their inner wall with stable, neutral coatings to control for EOF and prevent the protein from interaction with the wall [10]. During the focusing process, the two ends of the separation column should be maintained at the same level to eliminate the hydrodynamic flow. Under these conditions, at the end of the focusing process, all protein zones are stationary or near stationary within the separation column [3]. 

Chung S, Park SJ, Kim JK, Chung C, Han DC, Chang JK (2003) Plastic microchip flow cytometer based on 2- and 3-dimensional hydrodynamic flow focusing. Microsyst Technol 9 525-533. doi 10.1007/S00542-003-0302-2... 

In addition to the MFFD, another flow focusing device was first reported by Nisisako et al. [7] for the production of polymer particles. In that device, the hydrodynamic focusing of the dispersed phase is achieved thanks to two sheath fluids coming from both sides of the microchannel in which flows the dispersed phase (Figure 18.13, top). This sheath-flow microfluidic device (SFMD), etched in a quartz glass slab, was used in conjunction with a Y-junction to emulsify Janus droplets (Figure 18.13, middle). Two differently colored solutions of isobornyl acrylate (IBA) admixed with a small amount of a thermal initiator were fed to the... 

FIGURE 19.4 Flow-focusing cross-junction configuration for droplet formation. The center fluid (liquid A) is hydrodynamically focused by the continuous phase (liquid B) within the small orifice. Viscous forces overcome interfacial tension with thread instability in the enclosed orifice producing monodisperse droplets as rapidly as kilohertz frequencies. 

F. 9.14 2D microfluidic device using hydrodynamic flow focusing (data source from [33])... 

A 3D microfluidic device is a more recent development of hydrodynamic flow focusing, which helps to remove clogging in a 2D device [52, 53]. Thus, a 3D channel is a development over a 2D channel to improve the productivity. It has different inlets in the form of horizontal nozzles and vertical chimneys as shown in Fig. 9.15. It used PLGA-PEG as polymer. Acetonitrile (ACN) as solvent, and water as non-solvent. It produced nanoparticles of a small size in a controlled manner. 

There are different methods of nanoprecipitation, which are used to mix the two phases (organic and aqueous phases). To increase the yield and reduce the size of the nanoparticles, a proper method of mixing is necessary. The efiicient methods, like hydrodynamic flow focusing and CJIM were discussed with a common method like bulk pouring. Continuous efforts have been made to develop more efiicient configuration to precipitate nanoparticles and to improve the mixing with reduced mixing time. 

Rhee M, Valencia PM, Rodriguez MI, Langer R, Farokhzad OC, Kamik R (2011) Synthesis of size-tunable polymeric nanoparticles enabled by 3D hydrodynamic flow focusing in single-layer microchannels. Adv Mater 23(12) H79-H83... 

Miniaturisation of various devices and systems has become a popular trend in many areas of modern nanotechnology such as microelectronics, optics, etc. In particular, this is very important in creating chemical or electrochemical sensors where the amount of sample required for the analysis is a critical parameter and must be minimized. In this work we will focus on a micrometric channel flow system. We will call such miniaturised flow cells microfluidic systems , i.e. cells with one or more dimensions being of the order of a few microns. Such microfluidic channels have kinetic and analytical properties which can be finely tuned as a function of the hydrodynamic flow. However, presently, there is no simple and direct method to monitor the corresponding flows in. situ. 

The solid-liquid two-phase flow is widely applied in modern industry, such as chemical-mechanical polish (CMP), chemical engineering, medical engineering, bioengineering, and so on [80,81]. Many research works have been made focusing on the heat transfer or transportation of particles in the micro scale [82-88], In many applications, e.g., in CMP process of computer chips and computer hard disk, the size of solid particles in the two-phase flow becomes down to tens of nanometres from the micrometer scale, and a study on two-phase flow containing nano-particles is a new area apart from the classic hydrodynamics and traditional two-phase flow research. In such an area, the forces between particles and liquid are in micro or even to nano-Newton scale, which is far away from that in the traditional solid-liquid two-phase flow. 

Figure 2.45 Design of a multilamination mixer with hydrodynamic focusing (upper left) and flow pattern in such a mixer for a total volume flow of 10 ml h of water (lower left), taken from [141. The right side of the figure shows the orientation of liquid lamellae over a cross-section of the constriction for different Reynolds numbers [142].

This section focuses on steady and unsteady hydrodynamic modes that emerge as the rotational speed of the inner cylinder (expressed by Ta) and pressure-driven axial flow rate (scaled by Re) are varied, while the outer cylinder is kept fixed. These modes constitute primary, secondary and higher order bifurcations, which break the symmetry of the base helical Couette-Poiseuille (CP) flow and represent drastic changes in flow structure. Figure 4.4.2 presents a map of observed hydrodynamic modes in the (Ta, Re) space, and marks the domain where all of the hydrodynamic modes that interest us appear. We will return to this figure shortly. 

For the purpose of this study, particles are classified as Brownian or non-Brownian, where Brownian particles are defined as those for which the diameter is less than five microns and non-Brownian are those with diameter greater than five microns. The major focus of this work is on the second category. The particle release process has been studied both theoretically and experimentally, and it is found that for non-Brownian particles the surface charge and the electrolyte composition of the flowing phase are less significant factors than the hydrodynamic effects. However, Van der Waals forces are found to be important and the distortion of particles by these forces is shown to be crucial. 

A further option is to forget about simulating the flow and the processes in the whole vessel and to zoom into local processes by carrying out a DNS for a small box. The idea is to focus on the flow and transport phenomena within such a small box, such as mass transport and chemical reactions in or around a few eddies or bubbles, or the hydrodynamic interaction of a limited number of bubbles, drops, and particles including their readiness to collisions and coalescence. Examples of such detailed studies by means of DNS are due to Ten Cate et al. (2004) and Derksen (2006b). 

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