A study of multifilament yarn microstructure effects on polyester harp fog collection efficiency

Fog harvesting is an effective and low-cost strategy for meeting part of the water demand in fog-prone areas. However, the efficiency of conventional fog collectors is compromised by limitations in the effective collection and drainage of droplets. In this study, the fog collection efficiency of harp-based polyester multifilament fog collectors fabricated from partially oriented yarns (POY) and fully drawn yarns (FDY) was evaluated. The fog collection efficiencies of the harp structures were compared with those of three commercial fog collectors: Aqualonis (Cloudfisher), Ditf (FogHa-Tin), and Knitwire. The results revealed that polyester harp collectors exhibited a relative increase of 37–54% in fog collection efficiency compared with the Aqlo-back sample under the full-output condition. The structure based on 300 denier/48-filament FDY yarn exhibited the highest fog collection efficiency of 39.33% and the shortest onset time of 35 s. Capillary rise measurements showed that the initial water imbibition in the yarns follows the Lucas–Washburn model, whereas the equilibrium contact angle did not follow the scaling predicted by Jurin’s law. In addition, the dynamic contact angle was found to depend on the effective pore radius. The spatial arrangement of filaments in the FDY yarns resulted in loop-shaped filaments, which provide suitable sites for coalescing water droplets. Overall, the results demonstrated that FDY yarn-based harp structures, produced through a single-step draw-winding process, showed higher fog collection efficiency than the commercial samples.