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Impedance Sensors Made in PCB and LTCC Technologies for Monitoring Growth and Degradation of Pseudomonal Biofilm

Chabowski K., Junka A. F., Piasecki T., Nowak D., Nitsch K., Smutnicka D., Bartoszewicz M., Moczała M., Szymczyk P.

Metrology and Measurement Systems

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2017

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Vol. 24, nr 2

369--380

EN

The suitability of low-cost impedance sensors for microbiological purposes and biofilm growth monitoring was evaluated. The sensors with interdigitated electrodes were fabricated in PCB and LTCC technologies. The electrodes were golden (LTCC) or gold-plated (PCB) to provide surface stability. The sensors were used for monitoring growth and degradation of the reference ATCC 15442 Pseudomonas aeruginosa strain biofilm in invitro setting. During the experiment, the impedance spectra of the sensors were measured and analysed using electrical equivalent circuit (EEC) modelling. Additionally, the process of adhesion and growth of bacteria on a sensor’s surface was assessed by means of the optical and SEM microscopy. EEC and SEM microscopic analysis revealed that the gold layer on copper electrodes was not tight, making the PCB sensors susceptible to corrosion while the LTCC sensors had good surface stability. It turned out that the LTCC sensors are suitable for monitoring pseudomonal biofilm and the PCB sensors are good detectors of ongoing stages of biofilm formation.

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Simple Wide Frequency Range Impedance Meter Based on AD5933 Integrated Circuit

Chabowski K., Piasecki T., Dzierka A., Nitsch K.

Metrology and Measurement Systems

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2015

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Vol. 22, nr 1

13--24

EN

As it contains elements of complete digital impedance meter, the AD5933 integrated circuit is an interesting solution for impedance measurements. However, its use for measurements in a wide range of impedances and frequencies requires an additional digital and analogue circuitry. This paper presents the design and performance of a simple impedance meter based on the AD5933 IC. Apart from the AD5933 IC it consists of a clock generator with a programmable prescaler, a novel DC offset canceller for the excitation signal based on peak detectors and a current to voltage converter with switchable conversion ratios. The authors proposed a simple method for choosing the measurement frequency to minimalize errors resulting from the spectral leakage and distortion caused by a lack of an anti-aliasing filter in the DDS generator. Additionally, a novel method for the AD5933 IC calibration was proposed. It consists in a mathematical compensation of the systematic error occurring in the argument of the value returned from the AD5933 IC as a result. The performance of the whole system is demonstrated in an exemplary measurement.

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Porównanie elektrycznych właściwości mikroczujników impedancyjnych wykonanych na podłożach krzemowych i szklanych

Chabowski K., Piasecki T., Nitsch K., Gotszalk T., Sierakowski A., Grabiec P.

Elektronika : konstrukcje, technologie, zastosowania

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2014

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Vol. 55, nr 4

51-55

PL

Przedstawiono technologię wykonania, wyniki obliczeń oraz pomiarów parametrów elektrycznych mikroczujników impedancyjnych wykonanych na podłożu szklanym i krzemowym. Pomiary wykonywano w środowiskach modelowych: powietrzu, wodzie destylowanej i wodnym roztworze 0,9% NaCl. Ustalono, że czujniki wykonane na utlenionym krzemie wykazują bardzo duże sprzężenie pojemnościowe przez podłoże co negatywnie wpływa na ich czułość. Sprzężenie to można zniwelować poprzez uziemienie podłoża, niestety występuje wtedy dodatkowy efekt uboczny w postaci pojawienia się dodatkowej, pozornej rezystancji, pojemności i indukcyjności w mierzonym czujniku. W tym przypadku czujniki wykonane na szkle mają konstrukcję optymalną ze względu na niewielkie sprzężenie pojemnościowe przez podłoże.

EN

In this paper we presented a manufacturing technology, parameters calculation and electrical measurements results of impedance microsensors made on glass and silicon substrates. Measurements were held in model environments: air, distilled water and 0.9% NaCl aqueous solution. The sensors made on oxidized silicon express a large capacitive coupling through the substrate, which has a negative influence on its sensitivity. This coupling can be eliminated by grounding the substrate, however by doing this, an additional side effect occurs. The side effect relies on appearance of an additional apparent resistance, capacitance and inductance in measured sensor. In this case sensors made on glass has the optimal construction because of a low capacitive coupling.

4

Electrical properties of dielectric foil for embedded PCB capacitors

Piasecki T., Nitsch K., Dziedzic A., Chabowski K.

Materials Science Poland

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2012

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Vol. 30, No. 4

335--341

EN

One of the methods of achieving high packaging density of passive elements on the PCB is using the capacitors embedded in multilayer PCB. Test structures consisting of embedded capacitors were fabricated using the FaradFlexŽ capacitive internal layers. Impedance spectroscopy and equivalent circuit modelling was used to determine their electrical properties such as the capacitance, parasitic resistance and inductance. The use of several stages of accelerated ageing allowed us to test the durability of the structures. The results showed good quality stability of the embedded elements. The spatial distribution of the capacitance of the test structures on the surface of the PCB form was tested. The influence of the process parameters during lamination on the values of embedded capacitors was revealed.

5

Badanie wpływu alkoholi na odpowiedź funkcjonalizowanych czujników impedancyjnych

Chabowski K., Pałetko P., Nitsch K., Piasecki T., Grabiec P., Janus P., Gotszalk T.

Elektronika : konstrukcje, technologie, zastosowania

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2012

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Vol. 53, nr 6

53-55

PL

Przedstawiono wyniki badań funkcjonalizowanych chemicznie miniaturowych czujników impedancyjnych wykonanych w technologii krzemowej. Pomiary widm impedancyjnych i analiza elektrycznych modeli równoważnych sensorów zanurzonych w alkoholach wykazały występowanie relaksacji dielektrycznej w zakresie bardzo małych częstotliwości związanej z istnieniem dipolowych stanów energetycznych na powierzchni SiO₂/SAM/alkohol. Zaobserwowano korelację pomiędzy wartościami przenikalności elektrycznej alkoholi a pojemnością czujnika zmierzoną przy częstotliwości 1 MHz.

EN

The results of investigations of chemically functionalized miniaturized impedance sensors made on silicon were performed. Measurement of impedance spectra and analysis of the electrical equivalent circuit of sensors immersed in alcohols revealed the presence of dielectric relaxation in the range of very low frequencies. This relaxation was associated with the existence of dipole energy states on the surface of SiO₂/SAM/alcohol. There was a correlation between alcohol and the dielectric sensor capacitance measured at a frequency of 1 MHz.