Microchannel flow rate sensor based on impedance spectroscopy
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
12th Workshop of Chemical and Biological Micro Laboratory Technology
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
We propose an Electrical impedance-spectroscopy-supported (EIS) sensor concept, which measures the flow rate v and the test liquids conductivity ? inside a microchannel. Impedance spectroscopy is an analytical method for investigating the electrical properties of materials, particularly solids and electrolytes. The method is useful for basic research and e.g., development of batteries, fuel cells, sensors, corrosion protection or semiconductors. The principle of the sensor involves subjecting the liquid to a sinusoidal AC voltage and measuring the current response, generating complex impedance spectra for parameter evaluation. A connection between the measurement data and the physical properties of the liquid must be established. This is usually done via an electrical equivalent circuit diagram, whose behavior is as similar as possible to the real system. For our setup, we measure flow rate and conductivity by examining certain parameter changes of the systems equivalent circuit. Such flow measurements have already been shown for fixed ?. However, equivalent circuit parameters also change with conductivity ?, so various liquids will have different EIS responses for the same flow rate v. A change in v alters the circuits parameters and so does a change in ?. By now, other works neglect this change in ?, or only measure ? at a fixed frequency f, thus losing the equivalent circuit parameter information, aquired from the full impedance spectrum.
The influence of the volume flow and conductivity of the liquid on the impedance spectrum is given in the corresponding EIS plots, leading to an alteration of the fitting parameters in the equivalent circuit. The evaluation of this parameters, for both conductivity and flow rate simultaneously, will enable the adjustment for the influence of different conductivity liquids on the equivalent circuit parameters for flow rate measurements.
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