System Identification of Electrode-Skin Interface for Flexible PDMS Electrodes and Microelectrode Arrays
MetadataShow full item record
The objective of this research is to perform transfer function modeling of the electrode - skin interface using System Identification Toolbox (MathWorks, Inc. USA). This computational modeling is essential for developing dry electrodes that are used in transcutaneous electrical stimulation and bio-signal recording. Medical practitioners heavily rely on the information obtained from electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG). ECG and other bio-signals are constantly monitored in the hospitals. [1,3] Accurate diagnosis and treatment can be achieved by obtaining accuracy in monitoring of the bio-signals. This helps in delivering a high level of patient care. Patient monitoring system needs to be designed which can reproduce the measured signal to the highest replicability.  Distortions in the signal acquisition can be due to electrode - skin impedance which can cause misinterpretation of the signal.  Therefore, electrode - skin impedance measurement can provide valuable information regarding the quality of the signal.An important driver of the signal quality is how well the electrodes are electrically connected to the skin to detect relevant information from the signal rather than ambient noise. Since the information obtained from ECG, EEG, and EMG is of utmost importance to doctors and other medical practitioners, it is very important to create electrodes whose electrode-skin impedance is maintained as low as possible. In this work, we validate a method for electrode-skin impedance measurement using test circuit of flexible PDMS electrodes, electrolytic solution and a known resistor of 1k ohm. Different frequencies of the injected excitation voltage of 5V peak-to-peak provided an impedance spectroscopy of the media. This method can be used for many electrode configurations as well, e.g., 3-electrode configuration where a potentiostat controls the voltage difference between a Working Electrode and a Reference Electrode, and measures the current flow between the Working and the Counter electrodes. Transfer function model of the electrode - skin impedance was found to vary with different excitation frequencies as well as different electrolytic solutions that indicated resonance effects especially due to cracks (increased capacitance) in the flexible PDMS electrodes. In this work, we use this impedance spectroscopy method for PDMS electrodes, Multi-Electrode Arrays (MEAs) and for different electrolytic solvents.