Assessment of the Durability of Microelectrode Array Insulator Using Electrochemical Impedance Spectroscopy
Karttu, Antti (2018)
Karttu, Antti
2018
Automaatiotekniikka
Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences
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Hyväksymispäivämäärä
2018-06-06
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201805241815
https://urn.fi/URN:NBN:fi:tty-201805241815
Tiivistelmä
Microelectrode arrays (MEAs) are used to measure electrophysiological signals of cultured neuronal and cardiac cells. The simultaneous measurement of several parallel channels from planar electrodes enables monitoring of cellular activity in entire cell networks. Activity of cultured cell networks can be used for study of development and plasticity of cells, toxicology, disease modelling and pharmacological screening.
Performance of the MEA recordings is highly dependent on the impedance levels of the measurement electrodes, which have been widely studied. Conduction of signals is desired only through the surface of the opened electrodes, so an insulation layer is needed to separate the conductive tracks from the cell culture medium. Loss of insulation due to corrosion can result in the detection of signals outside the electrode surface, which leads to the loss of spatial information in the measurement.
A measurement method based on electrochemical impedance spectroscopy (EIS) was developed to assess the thickness and electrical properties of the insulation during exposure to cell culture media. A simplified test electrode array was designed and fabricated to study the durability of the insulator without the effect of opened electrodes. Two sample sets were fabricated with silicon nitride deposited at two different temperatures. The samples were immersed in three solutions and maintained at 37 °C for 16 days to study the stability of the insulator.
Decrease of insulator thickness and localized failures were detected on the tested samples from the impedance measurement data. Thickness estimates based on EIS were in good agreement with profilometer readings performed at the end of the experiment. Localized insulator failures were identified from the distinctive impedance waveforms. Corrosion of silicon nitride is suggested to occur by dissolution in water. Observed corrosion the insulator was extensive, which questions the use of silicon nitride as an insulator in physiological solutions. The presented measurement method can be used to study coating materials currently in use and for further testing and development of more durable alternatives.
Performance of the MEA recordings is highly dependent on the impedance levels of the measurement electrodes, which have been widely studied. Conduction of signals is desired only through the surface of the opened electrodes, so an insulation layer is needed to separate the conductive tracks from the cell culture medium. Loss of insulation due to corrosion can result in the detection of signals outside the electrode surface, which leads to the loss of spatial information in the measurement.
A measurement method based on electrochemical impedance spectroscopy (EIS) was developed to assess the thickness and electrical properties of the insulation during exposure to cell culture media. A simplified test electrode array was designed and fabricated to study the durability of the insulator without the effect of opened electrodes. Two sample sets were fabricated with silicon nitride deposited at two different temperatures. The samples were immersed in three solutions and maintained at 37 °C for 16 days to study the stability of the insulator.
Decrease of insulator thickness and localized failures were detected on the tested samples from the impedance measurement data. Thickness estimates based on EIS were in good agreement with profilometer readings performed at the end of the experiment. Localized insulator failures were identified from the distinctive impedance waveforms. Corrosion of silicon nitride is suggested to occur by dissolution in water. Observed corrosion the insulator was extensive, which questions the use of silicon nitride as an insulator in physiological solutions. The presented measurement method can be used to study coating materials currently in use and for further testing and development of more durable alternatives.