Mobile Health: Design of Flexible and Stretchable Electrophysiological Sensors for Wearable Healthcare Systems

Flexible and stretchable sensors have recently emerged as an active area of research for designing wearable, implantable and ingestible systems that allow pervasive and unobtrusive health monitoring in mobile health (m-Health) applications. Nevertheless, there lacks systematical study that compares the performances of these new types of sensors with their conventional counterparts. In this study, we reported the fabrication of serpentine-shape, flexible and stretchable electrodes that can be conformally attached to the skin via a printing-transfer process, and we introduced Area Density (AD) as a key parameter to guide the future design of these sensors. Sensors of AD 10, 20 and 40 percentages were designed and fabricated. The performances of these sensors for capturing one type of electrophysiological signals, i.e. electrocardiogram (ECG), were compared against ECG obtained by conventional gold and stainless steel metal clips. The results of this study found that flexible sensors designed with larger AD resulted in ECG of higher signal-to-noise ratio (SNR). In particular, ECG with SNR comparable to those measured by conventional metal clips (SNR>25dB) can be achieved when this new type of flexible sensors were designed with AD=40%. The results of this study shed light on the design of novel wearable and flexible electrodes, which can be used not only for on-body sensing but also in-body measurement inside the gastrointestinal tract.