MicroFluidizer Subject

Mapping of transport parameters in complex pore spaces is of interest for many respects. Apart from classical porous materials such as rock, brick, paper and tissue, one can think of objects used in microsystem technology. Recent developments such as lab-on-a-chip devices require detailed knowledge of transport properties. More detailed information can be found in new journals such as Lab on a Chip [1] and Microfluidics and Nanofluidics [2], for example, devoted especially to this subject. Electrokinetic effects in microscopic pore spaces are discussed in Ref. [3]. 

Quantitative entrapment of vaccines into small (up to about 200 nm diameter) liposomes in the absence of microfluidization (which can damage DNA and other labile materials when extensive) can be carried out by a novel one-step method (7) as follows SUVs (e.g., cationic) prepared as in section Preparation of Small Unilamellar Vesicles are mixed with sucrose to give a range of sucrose-to-lipid weight/weight ratio of 1.0 to 5.0 and the appropriate amount of plasmid DNA (e.g., 10-500 pg) and/or protein (e.g., up to 1 mg). The mixture is then rapidly frozen and subjected to dehydration by freeze-drying, followed by rehydration as in section Preparation of Vaccine-Containing Dehydration-Rehydration Vesicles. ... 

The content of vaccine within the small liposomes is estimated as in the section Estimation of Vaccine Entrapment in Dehydration-Rehydration Vesicles Liposomes for both microfluidized and sucrose liposomes and expressed as percentage of DNA and/or protein in the mixture subjected to freeze drying as in the section Preparation of Vaccine-Containing Small Liposomes by the Sucrose Method in the case of sucrose small liposomes or in the original DRV preparation (obtained in the section Estimation of Vaccine Entrapment in DRV Liposomes ) for microfluidized liposomes. Vesicle size measurements are carried out by PCS as described elsewhere (6,8,17). Liposomes can also be subjected to microelectrophoresis in a Zetasizer to determine their zeta potential. This is often required to determine the net surface charge of DNA-containing cationic liposomes. 

The various sample preparation methods mentioned in Section 5.6 have been tried in microfluidic devices off-line for biological and environmental matrices followed by analysis of the extracted samples by NLC and NCE. The available papers in the literature on this subject are discussed in the following sections. 

The last decade has been credited with major developments in microfluidic devices as many workers have reported on this subject. It is important to... 

Future markets for biomedical microdevices for human genome studies, drug discovery and delivery in the pharmaceutical industry, clinical diagnostics, and analytical chemistry are enormous (tens of billions of U.S. dollars).In the following sections, major bioMEMS applications and microfluidics relevant to bioMEMS applications are briefly introduced. Because of the very large volume of publications on this subject, only selected papers or review articles are referenced in this entry. 

We first introduce the basic concepts in physics of flow of simple and multiphase fluid in networks of microchannels. We then go on to demonstrate the phenomenology of the flow of droplets through the simplest network - a single loop of channels - and then provide examples of experiments on more complicated systems. The third part of the lecture introduces the subject of modeling of the dynamics of flow of units of resistance through networks of conductors, and show the results of these efforts and their correspondence to microfluidic flows. Finally, we provide an introduction to the subject of automation of flows of droplets in microchannels and demonstrate an example of the droplet-on-demand system constmcted in our laboratory. 

Microfluidics is also a cross-disciplinary subject that uses the methods and principles of microelectronics to construct very small analogs or models of such macroscopic fluidic elements as wind tunnels, valves, or fluidic amplifiers. The natural question that comes to mind is at what dimensional scale does fluid motion depart from the extremely well understood and well established laws of fluid dynamics There is no definitive answer to that question yet since the study of fluid motion in microscale and nanoscale structures is still at an early stage. 

To close this chapter, it should be clear that the future of this topic is as likely to be decided by researchers who are outside this field at present as the current students of the subject. The stroke of intuition that led a clinical chemist to use a microchannel to monitor sperm motility will undoubtedly be repeated in different venues for different problems. In light of the results obtained to date, there is every expectation that completely unique applications of microfluidics will arise shortly. 

Finally, a section summarizing the general advantages of microfluidic mixers/ reactors is presented. Although of high interest and importance, an in-depth review of microfluidic mixers in a diversity of microsystems for specific applications is not addressed since it falls out of the scope of this chapter. The reader is therefore directed to a number of excellent recent review articles on the specific subjects [9,19, 29-36]. 

Dealing with real fluids on the microscale is difficult. Bubbles, dust and surface tension can cause real problems due to the small size the fluid encounters. In fact, a whole science called microfluidics has built up and books have been written on the subject" Challenges to all microfluidic systems include ... 

Miniemulsions are typically formed by subjecting the oil/water/surfactant/ cosurfactant system to a high shear field created by devices such as an ultra-sonifier, the Manton Gaulin homogenizer and the Microfluidizer. These rely tn mechanical shear and/or cavitation to break the oil phase into submicron size droplets. When monomer is used as the oil phase, free radical polymerizatim can subsequently be carried out by addition of an initiator (e.g. potassium persulfate, KPS). 

Cheng X, Irimia D, Dixon M, Sekine K, Demrrci U, Zamir L, Tompkins RG, Rodriguez W, Toner M (2007) A microfluidic device for practical label-free CD4-I- T cell counting of HIV-infected subjects. Lab Chip 7 170-178... 

Cellular Mechanotransduction in Microfluidic Systems, Fig. 7 A novel microfabricated array that is capable of subjecting cyclic equibiaxial tensile strains of different magnitude, (a) Overview of a microarray mechanical stimulator, (b) Schematic cross-sectional... 

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