Electrochemical impedance spectroscopy (EIS) is a method for the non-destructive characterisiation of thin layers, membranes, surfaces and films. Typically a small amplitude AC voltage (or current) signal is applied to a sample while the amplitude and phase relationship of the corresponding current (or voltage) signal is monitored.
For an impedance spectrum, measurements are made over several decades of AC frequency with up to about 10 measurements per decade.
The results can be mathematically modelled, typically by treating the sample as a number of sublayers each with its own electrical resistance and capacitance. In particlular the capacitance and dielectric constant of each sublayer enables the thickness of that layer to be determined.
In other experiments sample impedance can be used for quantitative readings from biosensors.
eDAQ offers two EIS systems:
- ERZ100. This impedance system offers versatile performance at economical pricing and is suitable for many biosensor applications.
- INPHAZE HiRes EIS. This is a high resolution system where accuracy and precision are of paramount importance. It is capable of detectiing layer thicknesses down to atomic dimensions.