I work with planar interdigitated electrodes (IDEs). The finger width and the spacing between the fingers are 5 micron. The surface of the IDEs is coated by a non-conductive polymer layer (thickness is around 300-900 nm). This polymer layer acts as a transducer, where it was developed to detect target components (bacteria in particular). This biosensor chip is used for (non-faradaic) capacitive detection of target bacteria. The EIS measurements are performed with PBS solution without using any redox probes (under 0 DC voltage), and two electrode concept is employed.
Regarding the AC amplitude, some reports in literature mentioned that higher (e.g., >50mV) AC amplitude is required due to the insulating polymer layer. Would you agree on this approach? How important do you think to optimise the AC amplitude to achieve the best sensing performance?
What are the key points to be considered while deciding the AC amplitude and How do you decide an optimal AC amplitude for non-faradaic electrochemical impedance spectroscopy?
I usually use 5 mV and make a comparison with EIS spectra measured under 10 mV as Eac, but I can not see any difference. Obviously, this depends on the system I am working on it.
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