Chemical Microsensor: Precise conductivity measurements using planar electrodes

Chemical Microsensor: Precise conductivity measurements using planar electrodes

Dissertation

Microelectronics technologies are used increasingly to miniaturise sensors as well as with intelligent processing of signals (SMART sensors). Planar electrodes are used in chemical sensors, but only a few published work are focused on an influence development of the electrode structure in a detection of measured variables. In this work, the planar structure of electrodes was studied and simulated to find a suitable method for a precise conductivity measurement with possibility to integrate in a chip. Results have shown possible impedance behaviors of the planar electrodes under conductivity measurements of a electrolytic solution, a influence of technologies, and parasitic factors. A method of the bipolar pulse was studied to eliminate an influence of capacitance part of the sensor impedance on the measurement. The method was modified to solve problems with CMOS realisation which brings parasitic factors of circuits. Designed microsystem was submitted to patent. The chip was fabricated under a support of the program Europractice. The thick-film sensors with interdigital (combs) structure was fabricated and characterised.

Microelectronics technologies are used increasingly to miniaturise sensors as well as with intelligent processing of signals (SMART sensors). Planar electrodes are used in chemical sensors, but only a few published work are focused on an influence development of the electrode structure in a detection of measured variables. In this work, the planar structure of electrodes was studied and simulated to find a suitable method for a precise conductivity measurement with possibility to integrate in a chip. Results have shown possible impedance behaviors of the planar electrodes under conductivity measurements of a electrolytic solution, a influence of technologies, and parasitic factors. A method of the bipolar pulse was studied to eliminate an influence of capacitance part of the sensor impedance on the measurement. The method was modified to solve problems with CMOS realisation which brings parasitic factors of circuits. Designed microsystem was submitted to patent. The chip was fabricated under a support of the program Europractice. The thick-film sensors with interdigital (combs) structure was fabricated and characterised.

Conductivity, cell constant, interelectrode distance, interdigitated electrodes, thick-film, thin-film, bipolar pulse technique, double layer, interface impedance, Faraday impedance, Warburg impedance, thin-film, thick-film, ridge frequency, iterative adapting, cell constant correction factor, planar electrodes, spherical current, CMOS, chip

Conductivity, cell constant, interelectrode distance, interdigitated electrodes, thick-film, thin-film, bipolar pulse technique, double layer, interface impedance, Faraday impedance, Warburg impedance, thin-film, thick-film, ridge frequency, iterative adapting, cell constant correction factor, planar electrodes, spherical current, CMOS, chip

HUBÁLEK, J.

09.06.2003

Brno

Ph.D. THESIS

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