Pumping hydrodynamic

Fig. 4.1-5. Time behaviour of the fluid flow. A Hydrodynamic pump/compressor. B Hydrostatic (double-acting) piston machine. Vm Average flow V(t) time volume flow...

Lin, Y.H., Lee, G.B., Li, C.W., Huang, G.R., Chen, S.H., Flow-through sampling for electrophoresis-based microfluidic chips using hydrodynamic pumping. J. 

Microreactors provide a safe means by which reactions, including multistage schemes, can be undertaken where, otherwise, products involving unstable intermediates may be formed. This is exemplified by Fortt who showed that for a serial diazonium salt formation and chlorination reaction performed in a microreactor under hydrodynamic pumping, significant yield enhancements (15-20%) could be observed and attributed them to enhanced heat and mass transfer [77]. This demonstrates the advantage of microreactor-based synthesis where diazonium salts are sensitive to electromagnetic radiation and static electricity, which in turn can lead to rapid decomposition. Microreactors facilitate the ability to achieve continuous-flow synthesis, which is often not possible with conventional macroscale reactors and batch production. 

Fig. 4.18. (a) Schematic of PDMS microchip used for on-chip chemiluminescence assay. Reagents are loaded into inlets 1 and 2 and are hydrodynamically pumped towards outlet three. Light is generated when the two reagents mix. For detection a P3HT PCBM photodetector is placed underneath the detection chamber of the microchip, (b) Responsivity of the organic photodetector and emission spectra of the chemiluminescence dyes (Prom [21] - Reproduced by permission of The Royal Society of Chemistry)... 

Spence et al. employed a method by which endothelial cells were vacuum delivered into a channel that was coated with fibronectin. Li et al. described the use of a trough method for immobilizing a dopaminergic cell model. This method appears to be useful for cell types that have a tendency to cluster. Other methods have been described as well. In most cases, hydrodynamic pumping schemes have been employed for such immobilization determinations. ... 

Suzuki-Miyaura coupling Functionalised biphenols <76% Hydrodynamic pumping 2005/[42]... 

Typically, rapid repair of main cracks in slabs is realized using bituminous masses covering only the damages. Unfortunately, this kind of protection is ineffective just after few months of exploitation, because the degraded mass (Fig. 2b, 2c) allows for infiltration of water under slabs [8]. The coming into being hydrodynamic pump effect (due to moving loads - Fig. 3a) destructs sealants in joints (Fig. 3b) and causes uneven settlement of concrete slabs (Fig. 3c). The solution of this problem is the use of special polymer flexible joints. 

Figure 3. Scheme of the hydrodynamic pump effect (a) and caused by it damages of bituminous sealant (b, c) and the vertical movement of concrete slab forming fault (c)... 

Figure 2 SEM images of MIP monoliths fabricated inside capillary columns. Image a represents a polymer which is too dense and cannot undergo hydrodynamic pumping. Image b illustrates the other side of the spectrum where only a thin him of polymer remains, thereby compromising the capacity of the polymer. (Reproduced with permission from Ref 35.)...

Unfortunately, the commonly used imprinting solvents such as chloroform and toluene may not work for all systems. For example, in preparing an CEC monolith composed of functional monomers MAA, cross-linking monomer trimethylolpro-pane trimethacrylate (TRIM), and radical initiator 2,2 -azobis(isobutyronitrile) (AIBN), Schweitz et al. found that the use of toluene as the only porogenic solvent failed to produce sufiSciently porous monoliths [34]. The polymers produced using toluene were very dense and hydrodynamic pumping was not possible. Under these... 

In order to use the first method, the polymerization time and temperature must be carefully optimized through trial and error in order to achieve good flow-through properties. Too much polymerization results in a monolith that cannot be flushed via hydrodynamic pumping while lower degree of polymerization yields a small amount of polymer that the capacity is compromised. The tedious work necessary to optimize the polymer porosity is the main drawback of this method. The polymerization is often difficult to control. However, once conditions for polymerization are determined, the success rate for making the monoliths appropriately porous has been shown to be 100% [39]. 

The small size of these aggregates and the macroporous structure (200 A) helped with analyte diffusion and access to imprinted sites [38]. Wide interconnecting superpores (1-20 pm) surrounded the aggregates and permitted bulk flow and easy electrolyte exchange by hydrodynamic pumping. The protocol below details the procedures set forth by Schweitz to successfully prepare these columns [34,40-42]. 

One of the general ways for the fluid pumping is hydrodynamic pumping using HPLC pump or... 

Hydrodynamic, for instance, magneto-hydrodynamic pumps for which magnetic fields can induce currents in a moving conductive fluid... 

Fluids are often pumped hydrodynamically to exert the flow. Various pumps are used, including syringe pumps, peristaltic pumps, piezoelectric pumps, and gas-pressure-driven hydrodynamic pumps. In the case of hydrodynamic pumps, an inert gas is pressurized in the headspace of the vial containing the sample or carrier fluid. The force exerted by the gas on the liquid phase sustains flow of the liquid in the channel. When a liquid moves along the circular cross-section channel, the Poiseuille equation can be used to relate the... 

Alternatively, electrolyte solutions can be moved along microfluidic channels using elec-troosmotic flow (EOF see Chapter 6). In this case, an electric field rather than mechanical force is used to move the liquid. Implementation of EOF allows one to handle the backpressure problem associated with hydrodynamic pumping. However, EOF is mainly used to transport dilute aqueous electrolyte solution, and is sensitive to pH change. 

Microreactors provide a safe means by which reactions, including multistage schemes, can be undertaken where, otherwise, products involving unstable intermediates may be formed. This is exemplified by Fortt et al. who showed that for a serial chloro-diazotation Sandmeyer reaction performed in a microreactor under hydrodynamic pumping. 

Stojkovic, M., T. D. Mai, and P. C. Hauser. 2013. Determination of artificial sweeteners by capillary electrophoresis with contactless conductivity detection optimized by hydrodynamic pumping. Anal. Chim. Acta 787 254-259. 

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