A flexible and conformable dry electrode design on nonwoven fabrics is examined as a sensing platform for biopotential measurements. Due to limitations of commercial wet electrodes (e.g., shelf life, skin irritation), dry electrodes are investigated as the potential candidates for long-term monitoring of ECG signals. Multilayered dry electrodes are fabricated by screen printing of Ag/AgCl conductive inks on flexible nonwoven fabrics. This study focuses on the investigation of skin-electrode interface, form factor design, electrode body placement of printed dry electrodes for a wearable sensing platform. ECG signals obtained with dry and wet electrodes are comparatively studied as a function of body posture and movement. Experimental results show that skin-electrode impedance is influenced by printed electrode area, skin-electrode interface material, and applied pressure. The printed electrode yields comparable ECG signals to wet electrodes, and the QRS peak amplitude of ECG signal is dependent on printed electrode area and electrode on body spacing. Overall, fabric-based printed dry electrodes present an inexpensive health monitoring platform solution for mobile wearable electronics applications by fulfilling user comfort and wearability.

This article provides the latest advances from the NSF Advanced Self-powered Systems of Integrated sensors and Technologies (ASSIST) center. The work in the center addresses the key challenges in wearable health and environmental systems by exploring technologies that enable ultra-long battery lifetime, user comfort and wearability, robust medically validated sensor data with value added from multimodal sensing, and access to open architecture data streams. The vison of the ASSIST center is to use nanotechnology to build miniature, self-powered, wearable, and wireless sensing devices that can enable monitoring of personal health and personal environmental exposure and enable correlation of multimodal sensors. These devices can empower patients and doctors to transition from managing illness to managing wellness and create a paradigm shift in improving healthcare outcomes. This article presents the latest advances in high-efficiency nanostructured energy harvesters and storage capacitors, new sensing modalities that consume less power, low power computation, and communication strategies, and novel flexible materials that provide form, function, and comfort. These technologies span a spatial scale ranging from underlying materials at the nanoscale to body worn structures, and the challenge is to integrate them into a unified device designed to revolutionize wearable health applications.

An interface dipole model explaining threshold voltage $\left(V_t\right)$ tuning in HfSiON gated $n$ -channel field effect transistors $\left(n\mathrm{FETs}\right)$ is proposed. $V_t$ tuning depends on rare earth (RE) type and diffusion in $\mathrm{Si}∕\mathrm{Si}{\mathrm{O}}_x∕\mathrm{Hf}\mathrm{Si}\mathrm{O}\mathrm{N}∕{\mathrm{REO}}_x$ /metal gated $n\mathrm{FETs}$ as follows: $\mathrm{Sr}<\mathrm{Er}<\mathrm{Sc}+\mathrm{Er}<\mathrm{La}<\mathrm{Sc}<\text{none}$ . This $V_t$ ordering is very similar to the trends in dopant electronegativity (EN) (dipole charge transfer) and ionic radius $\left(r\right)$ (dipole separation) expected for a interfacial dipole mechanism. The resulting $V_t$ dependence on RE dopant allows distinction between a dipole model (dependent on EN and $r$ ) and an oxygen vacancy model (dependent on valence).