Time Evolution of the Skin–Electrode Interface Impedance under Different Skin Treatments

Abstract

A low and stable impedance at the skin–electrode interface is key to high-fidelity acquisition of biosignals, both acutely and in the long term. However, recording quality is highly variable due to the complex nature of human skin. Here, we present an experimental and modeling framework to investigate the interfacial impedance behavior, and describe how skin interventions affect its stability over time. To illustrate this approach, we report experimental measurements on the skin–electrode impedance using pre-gelled, clinical-grade electrodes in healthy human subjects recorded over 24 h following four skin treatments: (i) mechanical abrasion, (ii) chemical exfoliation, (iii) microporation, and (iv) no treatment. In the immediate post-treatment period, mechanical abrasion yields the lowest initial impedance, whereas the other treatments provide modest improvement compared to untreated skin. After 24 h, however, the impedance becomes more uniform across all groups (<20 kΩ at 10 Hz). The impedance data are fitted with an equivalent circuit model of the complete skin–electrode interface, clearly identifying skin-level versus electrode-level contributions to the overall impedance. Using this model, we systematically investigate how time and treatment affect the impedance response, and show that removal of the superficial epidermal layers is essential to achieving a low, long-term stable interface impedance.

Dependence of Skin-Electrode Contact Impedance on Material and Skin Hydration

“…Both Table 1 and Table 2 indicate the chi-squared value ranging from 0.7 × 10 −2 and 4.4 × 10 −2 for the fitting of the parameters to the circuit model. The obtained goodness of fit values is of the same order of magnitude as that of previous research works that depicted a good agreement between the fitting and experimental data [ 6 , 40 ].…”

“…The modeling parameters representing deeper tissue layers ( R d ), stratum corneum ( R sc , CPE sc ) and contact interface ( CPE c ) were computed by fitting the obtained impedance response. The fitting of the circuit parameters was restricted to lower and upper bounds, to avoid physically unreasonable values [ 6 ]. As per values found in the literature, R d was assigned 100 Ω–10 kΩ, R sc varied in the range of 10 kΩ–10 MΩ, and CPE sc ranged from 1–500 nSs α (S and s represent Siemen and seconds, respectively) with 0 < α ≤ 1 [ 6 , 17 ].…”

“…The fitting of the circuit parameters was restricted to lower and upper bounds, to avoid physically unreasonable values [ 6 ]. As per values found in the literature, R d was assigned 100 Ω–10 kΩ, R sc varied in the range of 10 kΩ–10 MΩ, and CPE sc ranged from 1–500 nSs α (S and s represent Siemen and seconds, respectively) with 0 < α ≤ 1 [ 6 , 17 ]. CPE c was assigned a wide range of 1–20,000 nSs β with 0.5 < β ≤ 1.…”

“…However, dry electrodes have an unstable electrochemical interface due to the absence of gel, which results in high and variable contact impedance, drift, and therefore low repeatability. Skin-electrode contact impedance plays a significant role in the performance of dry electrodes and a low skin-electrode contact impedance is desirable for the acquisition of a high-quality signal [ 6 ]. To achieve a lower skin-electrode contact impedance, it is important to understand the signal transfer mechanism occurring at the interface and the factors contributing to the skin-electrode contact impedance.…”

Биоимпедансный Анализ Состояния Поверхностных Тканей Пациента

“…Биоимпедансные измерения отдельных сегментов и локальных участков, в частности кожи и подкожной жировой ткани на произвольных участках тела паци-ента, с использованием стандартных методов, зондов и накладных электродов [7][8][9][10][11] затруднены вследствие большой площади поверхности тела, сложной структуры, а также существенного различия удельного электрического сопротивления кожи и подкожной жировой ткани пациента. Таким образом, можно констатировать, что существует потребность в новых биоимпедансных методах диагностики состояния и физиологических процессов в биологических тканях пациента, происходящих во время терапевтической обработки.…”