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Péclet number (Pe) - Nishanth Saldanha

59 bytes removed, 06:31, 23 March 2017
Applications to Microfluidics
== Applications to Microfluidics ==
[[Image:Tsensor.jpeg|150px|right|thumbnail|'''Figure 2''' Diffusion dominated mixing that occurs in a T-sensor makes it useful in florescence based analytical tests . The analyte (in grey) diffuses through the test stream]]
The low inertial forces present within many microfluidic setups , due to low velocity and length scales, often yield low Reynolds number flows <sup>[54]</sup> : low levels of turbulence can also be expected in these flow regimes. Thus convection is not prevalent in microfluidic setups, unless they are purposely induced Low length and velocity scales . Most mixing that do occur in microfluidic setups- > Low Reynolds number. This also implies lower convective forces when compared these devices occur due to larger devicesdiffusion [4]. As such, Pe in a microfluidic device Diffusion induced mixing is usually lower much slower than 1 and as suchconvective mixing, implying that these regimes are diffusion dominantwith mixing times in different order of magnitude. [Squires and Quake4]
This has an effect in making turbulence non existent in microfluidic devices. Turbulence in macro-world often leads to faster mixing -> Diffusion induced In units where quick mixing is slower than covective mixing not desired, such as many analytical tests or separation systems, low Pe is ideal. T->Slow sensors, as shown in different time scales (order figure 2, are an example of a class of minutes) [Squires and Quake]analytical devices that benefit from low Pe.
Thus, low Pe systems (Pe<1), have trouble getting good mixing -> If no mixing is desired, this can be optimal. However, in reaction systems, where mixing is necessary for reactions, Low Pe can be a hindrance [Squres and Quake]. While length of channels can be increased to increase Pe, this may not be optimal in all cases.

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