Dry Electrodes for Surface Electromyography Based on Architectured Titanium Thin Films

• Published in: Materials Vol. 13; no. 9; p. 2135
• Main Authors: S Rodrigues, Marco, Fiedler, Patrique, Küchler, Nora, P Domingues, Rui, Lopes, Cláudia, Borges, Joel, Haueisen, Jens, Vaz, Filipe
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 05.05.2020; MDPI
• Subjects: Athletes; biopotential electrodes; dry electrodes; Electrical resistivity; Electrocardiography; Electrodes; Electromyography; glancing angle deposition; Incidence angle; Irritation; magnetron sputtering; Medical research; Microstructure; Muscle function; Physical properties; Physiology; Plasma; Polyurethane resins; Porosity; Scanning electron microscopy; Signal quality; Silver chloride; Skin; Stainless steels; Substrates; Thin films; Titanium; Urethane thermoplastic elastomers; United States > US; biopotential electrodes; magnetron sputtering; glancing angle deposition; dry electrodes; electromyography; thin films
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma13092135

Electrodes of silver/silver chloride (Ag/AgCl) are dominant in clinical settings for surface electromyography (sEMG) recordings. These electrodes need a conductive electrolyte gel to ensure proper performance, which dries during long-term measurements inhibiting the immediate electrode's reuse and is often linked to skin irritation episodes. To overcome these drawbacks, a new type of dry electrodes based on architectured titanium (Ti) thin films were proposed in this work. The architectured microstructures were zigzags, obtained with different sputtering incidence angles (α), which have been shown to directly influence the films' porosity and electrical conductivity. The electrodes were prepared using thermoplastic polyurethane (TPU) and stainless-steel (SS) substrates, and their performance was tested in male volunteers (athletes) by recording electromyography (EMG) signals, preceded by electrode-skin impedance measurements. In general, the results showed that both SS and TPU dry electrodes can be used for sEMG recordings. While SS electrodes almost match the signal quality parameters of reference electrodes of Ag/AgCl, the performance of electrodes based on TPU functionalized with a Ti thin film still requires further improvements. Noteworthy was the clear increase of the signal to noise ratios when the thin films' microstructure evolved from normal growth towards zigzag microstructures, meaning that further tailoring of the thin film microstructure is a possible route to achieve optimized performances. Finally, the developed dry electrodes are reusable and allow for multiple EMG recordings without being replaced.