Valve passive

The structurally programmable micro fluidic system consists of passive valves and flow conduits, which provide different pressure drops. These pressure drops depend on the structure and surface properties of the fluidic paths. The pressure drops can be controlled by tailoring the length of the flow paths and the relative restriction ratio of the passive valves [71]. 

The hydrophobic passive valve was constructed at the junction of a narrow side channel and a wide main channel on a PDMS chip for liquid droplet... 

Jeon, N.L., Chiu, D.T., Wargo, C.J., Wu, H.K., Choi, I.S., Anderson, J.R., White-sides, G.M., Microfluidics section Design and fabrication of integrated passive valves and pumps for flexible polymer 3-dimensional microfluidic systems. Biomed. Microdevices 2002, 4(2), 117-121. 

Andersson H, van der Wijngaart W, Stemme G. Micromachined filter-chamber array with passive valves for biochemical assays on beads. Electrophoresis 2001 22 249-257. 

Figure 10-6 Example of a microfluidic valve constructed in silicon I200x 1200fxm) with an etched aperture to form the inlet for gas or liquid. The movable valve plate is supported by four polycrystalline-silicon arms,-400 jim long and 200 p,m wide, attached to the silicon substrate. (From Bien DCS, Mitchell SjN, Gamble HS. Fabrication and characterization of a micrornachined passive valve. J Micromech Microeng 2003 13 557-62.)...

Jeon NL et al (2002) Design and fabrication of integrated passive valves and pumps for flexible polymer 3-dimensional microfluidic systems. Biomed Microdevices 4(2) 117-121... 

Fig. 5 Determination of the chemotactic sensitivity of E. colt, (a) Schematic of the microfluidic device. Chemoattractant and fluorescein were injected in the microcapillary via inlet C by means of a passive valve, (b) Flow in the main channel (from A to B) was used to transport E. coll past the entrance (M) of the microcapillary, (c, d) Epifluorescence images of the microcapiflary filled with...

Solid Electrolyte-Ionic Electronic Transport Iron Passivation Valve Metals Dielectric Layers... 

Whether the total corrosion process is determined by the kinetics of anodic metal dissolution or the cathodic process depends on the size of the cathode and the kinetics of the partial electrode processes. The slowest reaction is the rate-determining step, as is usual in kinetics. In the case of a well-passivated valve metal, this is most probably the cathodic reaction, whereas for metals with semiconducting oxides, the rate-determining step win he anodic metal dissolution. In order to study the partial reactions of pitting corrosion separately, potentiostatic experiments are preferred. The cathodic process is replaced hy the electronic circuit of the potentiostat to investigate the anodic metal... 

This chapter has been structured into four sections firstly, the principles governing the centrifugal hydrodynamics on rotational platforms are briefly discussed. Next, externally actuated (active) and rotationally controlled ( passive ) valving schemes are outlined. To form fully integrated centrifugal LoaD platforms that can operate in a sample-to-answer fashion with low-complexity instrumentation, we finally present process automation of networked LUOs through novel, rotationally, and/ or event-triggered flow control schemes as well as common detection techniques. 

Active valving (Fig. 1) can offer more flexibility than passive valves but at the expense of greater instmmentation requirements and cost, particularly if they need to be synchronized with the rotational motion of the centrifugal cartridge. 

In recent years efforts have also been made to decouple the opening of passive valves from the spin rate. In so-called event-triggered operation, the arrival of liquid at dedicated points on the disc - rather than the rotational... 

Eurthermore, devices have been developed demonstrating reactions and passive valves with self-assembled monolayers of OTS via either multi-stream laminar flow or photolithography [12,13]. The pressure-sensitive valves were demonstrated with silane solutions and water with trace amounts of rhodamine-B for visualization... 

The rapid development of new methods of fabrication and microfluidic components enables the desired control and manipulation of small amounts of fluids. The microvalves in microelec-tromechanical systems (MEMS) are essential elements of a micro total analysis system. Typically, there are two types of microvalve one is the passive valve, the operation of which is dependent upon its surrounding pressure conditions, and the other is the active valve, which can be controlled actively. Active valves are categorized in three major ways initial working state, control pattern, and actuation principle. Each microvalve has advantages and disadvantages from the... 

Passive valves open and close as a consequence of the pressure distribution of the fluid at both side of the valve. They function as safety guards or as checker valves in a pump (next section). Active valves are controlled by signals from the system and therefore need an actuator to deliver the work for opening or closing the valve or put it in a correct position in a flow controller. Apart from the action, the actuators must be designed such, that they can maintain the valve position in a steady state. There are... 

A flapper is a passive valve that opens when the flow is below a set value to allow for the creation of a natural circulation circuit on the loss of forced flow. 

Large experimental facility (Integral Test Loop, ITL) is imder constmction the tests will include validation of the isolation condensers, large passive heat sink located within containment, passive valves, steam driven poison injection, passive ECCS of enhanced effectiveness, passive containment isolation, etc. 

Microfluidic valves are essential for flow control of sample and reagents on a microfluidic CD. There are two categories of valves, namely passive valves, and active valves. Passive valves have no moving parts and work on the principle of the capillary effect [6]. Active valves on the other hand require moving parts such as a membrane or plunger that requires external mechanical, pneumatic, electric or thermal force for actuation. 

Shut-down cooling through isolation condensers in gravity-driven water pool by opening passive valve... 

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