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Example: Electrokinetic valve. Introduction This model shows the modeling of electrokinetic flow in micro channels in MEMS, bio chips, and micro laboratories.

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Presentation on theme: "Example: Electrokinetic valve. Introduction This model shows the modeling of electrokinetic flow in micro channels in MEMS, bio chips, and micro laboratories."— Presentation transcript:

1 Example: Electrokinetic valve

2 Introduction This model shows the modeling of electrokinetic flow in micro channels in MEMS, bio chips, and micro laboratories. The model shows the combination of ready-to-use applications in COMSOL Multiphysics and the possibility of using free equation-based expressions in the edit fields. The model is solved using the electrokinetic flow application mode in the Chemical Engineering Module and the General Form in COMSOL Multiphysics Electrokinetic valve

3 Geometry and assumptions Model solved in two stages –Electric field and flow profile solved at steady-state in the focusing stage. –The concentration profile is calculated as a function of t for the injection and separation stages. –Supporting electrolyte is assumed, i.e. the concentration of the species does not influence the conductivity of the medium. Electrokinetic valve – Problem Definition Focusing Injection

4 Domain Equations, steady-state solution Focusing stage Electrokinetic valve – Problem Definition Momentum and global mass balance: Global charge balance for supporting electrolyte: Mass balance for diluted species:

5 Domain Equations, time-dependent problem Injection and separation stages Electrokinetic valve – Problem Definition Mass balance for solute: Global charge balance:

6 Boundary Conditions, focusing stage all inlets outlet all boundaries main inlet vertical inlets outlet Momentum and global mass balances: Global charge balance: Mass balance, solute: Electrokinetic valve – Problem Definition

7 Conditions, time-dependent injection and separation stages Electrokinetic valve – Problem Definition all other boundaries buffer inlet Initial condition obtained from the steady state solution

8 Concentration profile in the focusing, injection, and separation stages. Field configuration 1 Electrokinetic valve – Results Cross section plot Poor detachment gives pulse broadening

9 Concentration profile in the focusing, injection, and separation stages. Field configuration 2 Electrokinetic valve – Results Cross section plot Good detachment gives well-defined pulse

10 Concluding remarks The model is very simple to define and solve in COMSOL Multiphysics. The results agree with similar models from literature. The model is able to predict the field configuration that gives a well defined sample pulse in the sample channel. Electrokinetic valve – Concluding remarks


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