Abstract
In a new era for digital health, dry electrodes for biopotential measurement enable the monitoring of essential vital functions outside of specialized healthcare centers. In this paper, a new type of nanostructured titanium-based thin film is proposed, revealing improved biopotential sensing performance and overcoming several of the limitations of conventional gel-based electrodes such as reusability, durability, biocompatibility, and comfort. The thin films were deposited on stainless steel (SS) discs and polyurethane (PU) substrates to be used as dry electrodes, for non-invasive monitoring of body surface biopotentials. Four different Ti–Me (Me = Al, Cu, Ag, or Au) metallic binary systems were prepared by magnetron sputtering. The morphology of the resulting Ti–Me systems was found to be dependent on the chemical composition of the films, specifically on the type and amount of Me. The existence of crystalline intermetallic phases or glassy amorphous structures also revealed a strong influence on the morphological features developed by the different systems. The electrodes were tested in an in-vivo study on 20 volunteers during sports activity, allowing study of the application-specific characteristics of the dry electrodes, based on Ti–Me intermetallic thin films, and evaluation of the impact of the electrode–skin impedance on biopotential sensing. The electrode–skin impedance results support the reusability and the high degree of reliability of the Ti–Me dry electrodes. The Ti–Al films revealed the least performance as biopotential electrodes, while the Ti–Au system provided excellent results very close to the Ag/AgCl reference electrodes.
Highlights
Used conventional electrodes for biopotential recordings, in clinical and research applications, are silver–silver chloride (Ag/AgCl) based electrodes, in combination with electrolyte gels or pastes
In the study at hand, we focused on a comprehensive analysis of the electrode characteristics including chemical composition, structural composition, morphology, and the electrode
Ti–Me intermetallic thin films with different Me/Ti atomic ratios were deposited on different substrates to investigate their potential use as dry electrodes for biopotential sensing
Summary
Used conventional electrodes for biopotential recordings, in clinical and research applications, are silver–silver chloride (Ag/AgCl) based electrodes, in combination with electrolyte gels or pastes These electrodes present the characteristics of non-polarizable electrodes including outstanding reliability, and low, almost frequencyindependent skin contact impedance. Ag/AgCl electrodes are considered the gold standard for measurements involving low voltage signals of electrophysiological origin such as e.g., electromyography (EMG), electroencephalography (EEG), or electrocardiography (ECG). Despite their popularity, the gel-based electrodes present several considerable drawbacks such as short service life, extensive preparation time, and skin reaction ranging from liquid-related discomfort to eventual allergic contact dermatitis [1,2]. Dry electrodes are user-friendly solutions offering improved applicability without the need for hydrogels or other types of wet electrolytes [3,12,13,14,15,16,17]
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