Rotary Peristaltic Pump

Linear peristaltic pumps transport fluid through a flexible duct using traveling contraction waves. In a typical linear peristaltic pump, discrete translational elements rhythmically compress a straight section of flexible tube, moving fluid volumes. In contrast to rotary peristaltic pumps, linear peristaltic pumps usually do not use rollers or sliding contact elements. Because a moving boundary displaces fluid and induces the flow, linear peristaltic pumps are an example of positive-displacement pumps. 

Aschematic diagram of the flow injection system used by Anderson [126] is shown in Fig. 2.4. An Ismatec model MP13 peristaltic pump was used. Different flow rates were obtained by changing the pump tube diameter, as indicated in the legend to Fig. 2.4. The injection port was a rotary valve [131,170]. The sample volume could be varied between 10 and 1000 pi simply by changing the length of the sample loop. 

The mixing ability of microfluidic systems was tested using a rotary pump, a circular channel with inputs and outputs that can be peristaltically pumped, opeued, and closed. It was found that after only a few minutes of active mixing (due to pumping), a uniform mixture of particles is obtained that would have taken hours to achieve by diffusion. This is also useful for accelerating diffusion-... 

Although this seeems to be a difficult combination of conditions to achieve, it is in fact simple. Inexpensive rotary injection valves, such as those used for low-pressure liquid chromatography, will inject highly reproducible volumes. Dispersion and timing are also reproducible if a constant flow rate ( 1 %) is maintained in the reaction tube. Constant flow rates can be produced with peristaltic pumps. A simple FIA system can, therefore, be assembled from common components. 

While a linear pump can easily be bruit up from two or more basic actuation units, microscale rotary mechanisms face significant fabrication challenges. Accordingly, rotary peristaltic micropumps have seen very limited implementation. While several rotary mechanical micropumps are described in the literature (e.g., see the summaries in Refs. [1, 3], and [2]), to our knowledge there is only one example in the literature of a true rotary peristaltic micropump Kim et al. (Sensors and Actuators A 128 43—51, 2006) use a sflicmie membrane for the deformable charmel surface and a rotating ferrofluid plug... 

The individual actuators in a peristaltic pump can also serve as individual valves. Additional flexibility in integrating peristaltic pumps into large microfluidic systems can be gained from providing components with multiple functions. An example of this is the rotary mixer described in Ref. [12], which can serve as an effective dynamic micromixer or as a peristaltic pump, depending on the actuation pattern of the individual valves. 

The flow analyzer involves simple apparatus such as samplers, liquid drivers (peristaltic pumps, piston pumps, solenoid pumps), injection devices (rotary valves, injector-commutators), reactors and flow lines (usually narrow bore tubing), mixing chambers, and flow-through detectors. As a rule, these devices are readily available in most laboratories devoted to chemical analysis. Regarding detection, almost all analytical techniques have been used in flow analysis a small flow cell volume and a short response time that is compatible with system dynamics are important detector parameters. 

Apparatus. The flow injection system was composed of a model MV-CA4 peristaltic pump (Ismatec, Switzerland), a rotary injection valve (Ig Instrumenten Gesellschaft) and a perspex flow through cell (on loan from Ciba-Geigy). For longer term measurements under continuous flow conditions two electronically controlled valves were used in conjunction with the pump so that the electrode was exposed to either streams of carrier or sample. In all experiments the electrodes were controlled using... 

To conclude, Figure 5.8 depicts the operation of a peristaltic pump. The selection of a pump is sometimes constrained by non-mechanical considerations. In a peristaltic pump, the fluid flows in a flexible pipe which is independent from the pump mechanism. The hose is inserted into a circular cavity against whose surface it is forced by cylindrical rollers attached to a rotating hub. These rollers squeeze the hose at regular intervals. The fluid contained in the hose is driven by the rotation of the rotary hub. One benefit of such an apparatus is that the fluid is not in contact with the pumping mechanism. After use, the hose can be replaced if necessary. Peristaltic pumps are very simple to use. The use of small peristaltic pumps is very common in chemistry and biology, whenever product containment is required for safety reasons, or when the products can prove harmful for the mechanical parts (abrasion, corrosion, etc.). Less widely known is the existence of peristaltic pumps of significant size, whose flow rates can reach several tens of mVh. 

FIGURE 9,3 Manifold of the FIAD-HPLC system used for the determination of some food additives. Flow rate of carrier of donor and acceptor streams 0.2 mL/min. Pj and P2 peristaltic pumps 1 and 2 Ps, HPLC pump Vj manual-rotary injection valve V2 HPLC manual-rotary injection valve DC dialysis cell MXp mixing coil 1 (12 cm x 0.8 mm i.d.) MX2 mixing coil 2 (7.5 cm x 0.8 mm i.d.) Cisa Cjg analytical column Cigc Cxg guard column UV photodiode array detector and Wj, W2, W3, and W4 wastes 1, 2, 3, and 4. 

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