Microstructure and surface monitoring of ECG signals for CrTiN-Ni coatings as dry bioelectrodes

Abstract

The CrTiN-Ni coatings were fabricated using unbalanced magnetron sputtering. These coatings primarily consist of CrN and TiN crystalline phases, with a relatively high Ni content ranging from 52.4 at.% to 64.0 at.%. The coatings exhibit relatively low contact impedance with a Ni content of 58.9–61.0 at.%. The noise impedance (R_n) of the CrTiN-Ni coating dry electrodes ranges from 1.11–1.90 × 10⁶ Ω at a frequency of 1Hz, which is lower than that of the Ag/AgCl wet electrode (2.58 × 10⁶ Ω). In the static testing of electrocardiogram (ECG) signals, the signal power of CrTiN-Ni coated dry electrodes was measured to be 1.1 × 10⁻³ to 1.3 × 10⁻³ W, which is approximately one order of magnitude higher than that of commercial wet electrodes (7.2× 10⁻⁴ W). In dynamic measurements, the signal power of all coating dry electrodes consistently exceeded that of commercial wet electrode. Additionally, the coated dry electrodes exhibited a relatively high signal-to-noise ratio (SNR), ranging from 56.7 to 65.1 dB, which is comparable to that of commercial wet electrodes (63.3 dB). This suggests that coated dry electrodes have considerable potential for use as dry bioelectrodes in practice.