RESUMEN
Flexible piezoresistive pressure sensors have received great popularity in flexible electronics due to their simple structure and promising applications in health monitoring and artificial intelligence. However, the contradiction between sensitivity and detection range limits the application of the sensors in the medium-pressure regime. Here, a flexible piezoresistive pressure sensor is fabricated by combining a hierarchical spinous microstructure sensitive layer and a periodic microsphere array spacer. The sensor achieves high sensitivity (39.1 kPa-1) and outstanding linearity (0.99, R2 coefficient) in a medium-pressure regime, as well as a wide range of detection (100 Pa-160.0 kPa), high detection precision (<0.63 full scale), and excellent durability (>5000 cycles). The mechanism of the microsphere array spacer in improving sensitivity and detection range was revealed through finite element analysis. Furthermore, the sensors have been utilized to detect muscle and joint movements, spatial pressure distributions, and throat movements during pronouncing words. By means of a full-connect artificial neural network for machine learning, the sensor's output of different pronounced words can be precisely distinguished and classified with an overall accuracy of 96.0%. Overall, the high-performance flexible pressure sensor based on a microsphere array spacer has great potential in health monitoring, human-machine interface, and artificial intelligence of medium-pressure regime.
RESUMEN
Nanofiber-based air filters and electrostatic precipitation have stimulated considerable interest because of their high-efficiency for PM2.5 capture. In this paper, we introduce a new method of in situ electrospinning (e-spinning) of nanostructures into a polluted enclosed space to efficiently clean the air. From the comparisons of different polymer precursors and different PM2.5 capture techniques, it can be seen that in situ e-spinning of chitosan aqueous solution into the air exhibits the best PM2.5 capture efficiency, which may be attributed to the stronger polarity of chitosan and the synergistic effect of the strong electrostatic adsorption and surface adhesion of the electrospun (e-spun) nanofibers. A removal rate as high as 3.7 µg m-3 s-1 was obtained using this technology with a high efficiency of more than 95% PM2.5 capture. The results obtained from a field test in a smoking room (â¼5 × 6 × 3 m3) are still in great agreement with those obtained in an experimental box (â¼25 × 30 × 35 cm3). More importantly, chitosan is non-toxic and biodegradable, and is harmless to human health when used as a precursor for in situ e-spinning for PM2.5 capture.
