Electrode-skin impedance changes due to an externally applied force

The objective of this research is to analyze the effect of an externally applied force on surface biopotential electrodes. Electrode-skin impedance is an important factor in biopotential measurements. Lower electrode-skin interface impedance is desired because it improves the measurement of biological signals and helps mitigate noise/artifacts. Electrode-skin interface impedance was measured from two subjects (from 1 Hz to 1 MHz) while applying different magnitudes of force (0 N, 8.8 N, and 22.3 N) on Ag/AgCl electrodes that were placed on the ventral side of the forearm. When 8.8 N of force was applied, the impedance at 10 Hz decreased compared to when there was no externally applied force. Increasing the applied force to 22.3 N produced inconsistent results between the two subjects, with one exhibiting an increase in impedance, while the other a decrease. When all applied forces were removed from the electrodes, there was a sustained decrease in impedance, as compared to the initial impedance with no externally applied force. An externally applied force can reduce the electrode-skin impedance, which is maintained even after the force was removed.