Elastic Textile Threads for Fog Harvesting.

ABSTRACT

The potential applications of textile materials in fog harvesting have long been demonstrated. This work designed novel fog harvesters according to the distinct features of elastic textile threads (ETTs) to enhance droplet capture, large-droplet growth, and droplet pouring and improve fog harvesting efficiency. We prepared m@ETTs (modified ETTs) using three novel chemical and physical methods. First, we prepared spandex elastic threads with a non-uniform rough surface containing silica nanoparticles and titanium particles through the sol-gel triethoxymethylsilane method. Second, we prepared a rubber/polyester thread with a rough surface by breaking the thread shell with toluene solution, creating knots on the surface of the rubber core. Third, we prepared a polyurethane thread with a bumpy superhydrophobic surface by spraying a tetrafluoroethylene adhesive and silica nanoparticles on the thread. Furthermore, we connected ETTs to an automatic stretching-recovery system to obtain auto-ETTs as another group of harvesters. We obtained auto-i@ETTs by introducing elastic bumps/knots onto the auto-ETT surface. The fog harvesting efficiencies of m@ETTs were approximately 60-120% greater than those of the ETTs. The water harvesting rate of the auto-i@ETT was 2.5 times that of the ETT, with the highest water harvesting rate of auto-i@ETT reaching 3.35 g/h/cm2. Moreover, several novel principles of droplet behavior and thread elasticity were revealed. The elastic elongation level of the ETTs was proportional to their water harvesting efficiency. The stretching-recovery state of the elastic thread did not influence the water contact angle but affected the droplet state on the thread surface. The temporary slack/stick state of adjacent elastic threads on auto-ETTs contributed to droplet convergence and pouring. Overall, this novel approach demonstrates the significant potential of elastic threads in fog harvesting applications.