In situ assembly of well-dispersed Ag nanoparticles throughout electrospun alginate nanofibers for monitoring human breath - smart fabrics.

Alginate nanofibers assembled with sliver nanoparticles throughout the whole nanofiber were fabricated by three steps including electrospinning of Na-alginate nanofibers, ion exchange between the sodium and silver ions, and in situ reduction of silver nanoparticles. The content, distribution and size of the nanoparticles are controllable by tuning reaction conditions. Ag/alginate nanofibers exhibit good humidity sensitivity in a wide humidity range from ambient RH (20%) to 85% RH. Interestingly, these humidity sensors can be attached to a 3M-9001V mask for monitoring human breath during exercise and emotion changes, and this smart exhibits accurate and continuous human-breath tracking no matter how fast or slow as well as how deep or shallow. The obtained frequencies of respiration during normal, running, delight and sadness conditions were 16, 13, 14 and 8 times min-1, respectively. Moreover, the signal waveform obtained under emotion changes is distinguishable, implying its potential applications in lie detection and interrogation. Thanks to this smart mask could accurately capture the rate and depth of the respiration, providing an effective, low-cost and convenient approach for tracking respiration, it was utilized as smart fabrics in avoiding sleep apnea.