Spray-Coated, Magnetically Connectable Free-Standing Epidermal Electrodes for High Quality Biopotential Recordings

Acquiring biopotentials from the surface of the body is a common procedure both in the clinical practice and in non-clinical applications as sport and human- machine interfaces. To avoid bulky recording systems and to allow optimal long-term measurements, several tattooable solutions were recently developed, aiming at high-quality and imperceptible electrodes. However, a seamless connection with epidermal electrodes still represents one of the biggest challenges in this field. In this paper, we propose a simple and efficient approach for the fabrication of free-standing epidermal electrodes that can be contacted using small magnetic connectors, thus directly tackling this issue. The proposed electrodes are fabricated using a conductive ink based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) deposited by spray coating, and can be easily contacted using magnetic connectors without disrupting their conformability, thanks to the presence of ferrite nanoparticles integrated within the thin film itself. These electrodes have been successfully employed for the detection of different biopotentials, namely electrocardiogram, electromyogram and electro-oculogram, demonstrating excellent performances for the detection of biosignals from delicate body parts, such as the face, thus demonstrating the effectiveness of the approach for the development of a new generation of magnetically connectable epidermal electrodes for critical biopotentials monitoring.