Development of a conductivity microsensor considering electric double layer capacity

An electrochemical sensor of a novel design has been developed for the electric sensing of conductive particles in a solution. System is made of PMMA plastic (plexiglass) by means of UV lithography and galvanic electroplating to assure a low manufacturing cost. Our sensor consists of a gold microelectrode array embedded in plexiglass. Sensor design allows the simple integration of control electronics. Sensor characteristics were investigated by the impedance spectroscopy and its functionality examined by the conductivity measurement. The effect of ion concentration on the impedance spectra was studied. Three electrode fields with different characteristic electrode dimension of 250, 100 and 50 μm were manufactured and scale-down effects were verified. The impedance responses of the sensor are interpreted through an equivalent RC circuit. Capacitive dispersion of the electric double layer (EDL) impedance was discovered and the substitution by the constant phase element (CPE) is discussed.

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► Gold microelectrode array sensor conductivity sensor has been developed.
► Sensor functionality was examined by the impedance spectroscopy.
► Data was interpreted through the equivalent circuit.
► Scale-down behavior was deduced from measured data.
► Strong non-ideal polarization occurred and is discussed.