Lightweight portable sensors for health care

In this article, textile electrodes and semiconductor thin film piezoresistive sensors on plastic substrates were manufactured and fabricated with CMOS processes, respectively. An armband made of plain weave fabric, integrating embroidery textile electrodes of stainless steel (SS) and elastics to conform to human forearms were manufactured. The textile electrodes with an area of 1cm2 were made of two stitching layers for ease of manufacture and electrode robustness and connected through snap fasteners and SS/cotton threads to a signal processing electronic module. Piezoresistive sensors, consisting of n-type hydrogenated nanocrystalline silicon thin films patterned into rectangular bars and having metallic thin leads connecting the sensor to large pads were fabricated on 25µm thick flexible (polyimide) substrates. The textile and thin film piezoresistive sensors were connected to a small lightweight signal processing electronic module of a wireless portable unit for real-time monitoring and recording of the sensors signals. Surface electromyography signals of the forearms of a volunteer wearing the armband with textile electrodes exhibit amplitudes and baseline noise levels comparable to those obtained with standard Ag/AgCl electrodes. The piezoresistive sensor on plastic substrate was stuck with grease to the neck of a volunteer and small front/back neck movement monitored and recorded.