Survey on Textile Electrode Technologies for Electrocardiographic (ECG) Monitoring, from Metal Wires to Polymers

Wearable technologies represent the new frontier of vital sign monitoring in different applications, from fitness to health. With the progressive miniaturization of the electronic components, enabling the implementation of portable and hand-held acquisition and recording devices, the research focus has shifted toward the development of effective and unobtrusive textile electrodes. These electrodes can represent an alternative to the Ag/AgCl disposable gelled electrodes usually adopted in clinical practice. This survey presents the main requirements for these electrodes, with a particular emphasis on those conceived for electrocardiographic signals, and the main challenges to be faced. An overview of the main materials and fabrication technologies presented so far in the scientific literature for this purpose is also given. The pieces of evidence resulting from the test of these electrodes clearly reveal the virtues and vices of current technologies, prospectively opening to their use in smart garments for real application scenarios.