An impedance model to estimate the effective active area of neuro-electrode for quality control

Numerous studies have demonstrated the effectiveness of electrical stimulation as a therapy to treat a wide range of deficits. In particular, the design of more sophisticated neuro-electrodes has led to major breakthroughs in the field. However, these new electrodes are generally manufactured in laboratories in a semi-manual, non-industrial way. As a result, there can be considerable variability in the dimensions of the electrodes manufactured, particularly in the final surface area of the electrode active sites. In this paper, we explore the use of impedance measurement as a tool for estimating the post-manufacturing effective surface area of active sites. LIFEs with variable active site sizes and electrical impedance spectroscopy were used to evaluate the approach. The relationship between impedance and active surface area was estimated by two methods: a direct method based on single frequency impedance measurement, and an indirect method based on parameter extraction from a serial R-CPE model and whole impedance spectrum. Both methods were successful in providing an accurate estimate of the active site area, with an advantage for the second method, which achieves an estimation error of less than 5%.