Fluidic high-pressure

Reactor 5 [R 5] Specially High-pressure Fluidic Interconnect - Chip-to-chip... 

The thin and sheet-like design of the micro mixer makes an interconnect with a fluidic environment difficult Also the small external dimensions of the micro mixer (see Table 4.3) cause some problems, e.g. the access ports are smaller than most off-the shelf parts, handling of the chip itself is difficult and tedious, the distances between inlet and outlet holes are very small, the chip is made from a brittle material, and consequently, high pressures cannot be applied by clamping [70],... 

The concept presented here in much detail as an example of cooperative project work in micro structured reactor plant development is based on the bus system and simultaneously handles a number of tasks such as mechanical stability, fluidic flow and signal transmission. A key feature of the so-called backbone interface is its open architecture. It does not rely on standardized reactors or devices, thus allowing the combination of devices from various suppliers. A robust interface was developed which withstands high pressures and temperatures. Thermal cross-talk was minimized through the use of different heat-conducting materials. 

Modern pumps have more features and better reliability and performance than earlier models because of better designs in seals, pistons, and check valves as well as innovations such as dual-piston in-series and piston seal wash.2 Performance at low rates can be improved by variable stroke mechanism, micro pistons, or active check valves. The fluidic components in more inert pumps for bio-purification or ion-chromatography are often constructed from titanium or polyetheretherketone (PEEK). Low-pressure mixing quaternary pumps have become standard equipment in research laboratories whereas high-pressure mixing pumps are popular for LC/MS, HTS, and micro LC applications. 

FIGURE 3.27 An elastomeric peristaltic pump using three valve control channels. The fluidic channel is 100 pm wide and 10 pm high. Dimension of microvalve control channels = 100 pm by 100 pm by 10 pm applied air pressure = 50 kPa. Peristalsis was typically actuated by the pattern 101, 100, 110, 010, Oil, 001, where 0 and 1 indicate valve open and valve closed, respectively [167]. Reprinted with permission from the American Association for the Advancement of Science. 

Also known as gradient delay volume, system dwell volume is the liquid holdup volume of the HPLC system from the point of solvent mixing to the head of the column. This includes the additive volumes of the injector, the sample loop, all fluidic connection tubing, and any internal pump volumes of a low-pressure mixing system. The typical dwell volume of a modem HPLC is 0.5-2 mL, but can be as high as 5-7 mL in older systems. 

Based on the high elasticity of PDMS, the elementary microfluidic unit operation is a valve which is typically made of a planar glass substrate and two layers of PDMS on top of each other. One of the two elastomer layer contains the fluidic ducts while the other elastomer layer features pneumatic control channels. To realize a microfluidic valve, a pneumatic control channel crosses a fluidic duct as depicted in Fig. 9a. A pressure p applied to the control chaimel squeezes tlie elastomer into the lower layer, where it blocks the liquid flow. Because of the small size of this valve in the order of 100 x 100 pm, a single integrated fluidic circuit can accommodate thousands of valves. Comparable to developments in microelectronics, this approach is called microfluidic large scale integration (LSI) [122]. 

A high degree of temporal control over the (micro)fluidics is a prerequisite to carry out time-dependent studies of (bio)chemical reactions. In the MALDI-based lab-on-a-chip device described here the fluid is transported through the microchannels due to a pressure difference between the inlet, where a small air bubble is present (atmospheric pressure), and the outlet (vacuum). The relation between the generated flow rate and the applied vacuum pressure is defined by the equation41,42... 

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