Wearable Multi-Biosignal Analysis Integrated Interface with Direct Sleep-Stage Classification

This paper presents a wearable multi-biosignal wireless interface for sleep analysis. It enables comfortable sleep monitoring with direct sleep-stage classification capability while conventional analytic interfaces including the Polysomnography (PSG) require complex post-processing analyses based on heavy raw data, need expert supervision for measurements, or do not provide comfortable fit for long-time wearing. The proposed multi-biosignal interface consists of electroencephalography (EEG), electromyography (EMG), and electrooculography (EOG). A readout integrated circuit (ROIC) is designed to collect three kinds of bio-potential signals through four internal readout channels, where their analog feature extraction circuits are included together to provide sleep-stage classification directly. The designed multi-biosignal sensing ROIC is fabricated in a 180-nm complementary metal & x2013;oxide & x2013;semiconductor (CMOS) process. For system-level verification, its low-power headband-style analytic device is implemented for wearable sleep monitoring, where the direct sleep-stage classification is performed based on a decision tree algorithm. It is functionally verified by comparison experiments with post-processing analysis results from the OpenBCI module, whose sleep-stage detection shows reasonable correlation of 74% for four sleep stages

Batch Nanofabrication of Suspended Single 1D Nanoheaters for Ultralow-Power Metal Oxide Semiconductor-Based Gas Sensors

The demand for power-efficient micro-and nanodevices is increasing rapidly. In this regard, electrothermal nanowire-based heaters are promising solutions for the ultralow-power devices required in IoT applications. Herein, a method is demonstrated for producing a 1D nanoheater by selectively coating a suspended pyrolyzed carbon nanowire backbone with a thin Au resistive heater layer and utilizing it in a portable gas sensor system. This sophisticated nanostructure is developed without complex nanofabrication and nanoscale alignment processes, owing to the suspended architecture and built-in shadow mask. The suspended carbon nanowires, which are batch-fabricated using carbon-microelectromechanical systems technology, maintain their structural and functional integrity in subsequent nanopatterning processes because of their excellent mechanical robustness. The developed nanoheater is used in gas sensors via user-designable localization of the metal oxide semiconductor nanomaterials onto the central region of the nanoheater at the desired temperature. This allows the sensing site to be uniformly heated, enabling reliable and sensitive gas detection. The 1D nanoheater embedded gas sensor can be heated immediately to 250 degrees C at a remarkably low power of 1.6 mW, surpassing the performance of state-of-the-art microheater-based gas sensors. The presented technology offers facile 1D nanoheater production and promising pathways for applications in various electrothermal devices