MicroChannel structures

Peng, X. F., Wang, B. X., Cooling characteristics with microchanneled structures, J. Enhanced Heat Transfer 1 (1994) 315-326. 

Zhu et al. [76] designed and fabricated microfluidic devices on polymethylmethacrylate (PMMA) substrates for electrochemical analysis applications using an improved UY-LIGA process. The microchannel structures were transferred from a nickel mold onto the plastic plates by the hot embossing... 

The distinguishing feature of membrane emulsification technique is that droplet size is controlled primarily by the choice of the membrane, its microchannel structure and few process parameters, which can be used to tune droplets and emulsion properties. Comparing to the conventional emulsification processes, the membrane emulsification permits a better control of droplet-size distribution to be obtained, low energy, and materials consumption, modular and easy scale-up. Nevertheless, productivity (m3/day) is much lower, and therefore the challenge in the future is the development of new membranes and modules to keep the known advantages and maximize productivity. 

Gosch, M., Blom, H., Holm, J., Heino, T., Rigler, R., Hydrodynamic flow profiling in microchannel structures by single molecule fluorescence correlation spectroscopy. Anal. Chem. 2000, 72, 3260-3265. 

Kitamori s group has proposed selective chemical surface modification utilizing capillarity (called the capillarity restricted modification or CARM method) (Hibara et al., 2005). In the CARM method, a microchannel structure combining shallow and deep microchannels and the principle of capillarity are utilized. The procedures are shown in Figure 19. A portion of an ODS/toluene solution (lwt%) is dropped onto the inlet hole of the shallow channel, and the solution is spontaneously drawn into this channel by capillary action. The solution is stopped at the boundary between the shallow and deep channels by the balance between the solid-liquid and gas-liquid interfacial energies. Therefore, the solution does not enter the deep channel. It remains at the boundary for several minutes and is then pushed from the deep channel side by air pressure. 

Design of microchannel structures for respective synthesis purposes... 

Peng, X.F. and Peterson, G.P., Convective Heat Transfer and Flow Friction for Water Flow in MicroChannel Structures, Int. J. Heat Mass Transfer, 1996, 39(12), 2599-2608. 

Positive tone resins based on a photoacid generator and either a random copolymer of tetrahydropyranyl methacrylate and methyl methacrylate [137] or random copolymers of tetrahydropyranyl methacrylate, methyl methacrylate, and t-butyl methacrylate (180) were used for fabrication of 3D microchannel structures [264], Simple placed channels connected to cubic or prismatic trenches, which are open to the surface as well as optical grating structures, comprise a set of several parallel channels placed about 10 pm below the surface with connecting reservoirs on both ends. They were fabricated by positive TP microlithography (Fig. 3.75) [264]. 

FIGURE 51.1 Schematic diagram of the general processing steps involved in the fabrication of microchannel structures using sacrificial materials. 

R. Willingale and G. W. Fraser. Broad band X-ray imaging with microchannel structures. In preparation. 

In the same years, new methods to fabricate open microchannel structures in silicon or glass substrate using various etching techniques were developed, such as reactive ion etching, hydrofluoric acid, or potassium hydroxide wet etching. 

Biochemical analysis on nanoliter scale is precisely carried out by micrototal analysis system (pTAS) which consists of microreactors, microfluidic systems, and detectors. Performance of the pTAS depends on micromachined and electrochemically actuated micropump capable of precise dosing of nanoliter amounts of liquids such as reagents, indicators, or calibration fluids [28]. The dosing system is based on the displacement of the liquid from a reservoir which is actuated by gas bubbles produced electrochemically. Electrochemical pump and dosing system consist of a channel structure micro-machined in silicon closed by Pyrex covered with novel metal electrodes. By applying pulsed current to the electrodes, gas bubbles are produced by electrolysis of water. The liquid stored in the meander is driven out into the microchannel structure due to expansion of gas bubbles in the reservoir as shown in Fig. 11.8. 

The larger inertia of denser CTCs has also been used to isolate them on the microscale. MicroChannel structures such as herringbones can be used to induce secondary vortex flows which can promote movement of cells so that wall adhesion is promoted. Similarly, curved microchannels can induce Dean flows, which will laterally displace cells based upon their inertia. 

In this section, numerical simulations of the Joule heating-induced temperature field and the sample solute concentration distributions in a microchannel structure with a step change in cross section (see Fig. 2) will be presented. Because the total current passing through a dielectric channel is constant, the current density in the narrow channel is higher than that in the wide channel. As shown in Eq. 10, the Joule heating is proportional to the second power of the current density, so more heat is generated in the... 

A system for microchannel structures has been described that is particularly useful for the high precision delivery of drugs (52). 

X. F. Peng, G. P. Peterson, Convective heat transfer and flow friction for water flow in microchannel structures. International Journal of Heat and Mass Transfer, 1996, 39, 2599-2608. 

Figure 25.9 Scheme of the reactor housing (left) and photograph (middle) ofthe heat-shielded reactor under operation (gold mirror becomes transparent) [40] and different reactor sizes (right inset magnification of microchannel structure) [47]. 

---