Flexible ATO/CNT/rGO composite electrodes with high conductivity for superior ECG signal fidelity

The development of skin-compatible, high-conductivity electrodes is essential for reliable wearable electrocardiogram (ECG) monitoring. A novel ternary antimony (Sb)-doped tin oxide hybridized with carbon nanotubes and reduced graphene oxide (ATO-CNT-rGO) was developed using a solid-state technique. X-ray diffraction (XRD) confirmed the preservation of the rutile ATO phase, while Raman spectroscopy revealed a balanced defect density (I_D/I_G) in the CNT-rGO network, which enabled efficient charge transport. Scanning Electron Microscopy (SEM) revealed a well-connected 1D-2D carbon framework anchored onto the ATO nanoparticles, forming a continuous percolation pathway. IV-point probe measurements demonstrated that the ternary composite exhibited the highest conductivity (193.2 S/m), which was approximately four times greater than that of pure ATO. Electrochemical Impedance Spectroscopy (EIS) showed low skin-to-electrode impedance (50 kΩ at 10 Hz). The screen-printed hybrid material's flexible dry electrode delivered high-fidelity ECG signals with clear P-QRS-T waveforms compared to the screen-printed Ag/AgCl electrodes. It exhibited an enhanced signal-to-noise ratio (SNR) of 15:1 after filtering, significantly outperforming the Ag/AgCl electrode. It has a stable skin-electrode interface, which validates the material's suitability for wearable bioelectronics applications. This study established ATO-CNT-rGO hybrids as viable alternatives to conventional electrodes for next-generation low-noise flexible wearable ECG monitoring systems.