Wettability gradient of photoresponsive electrospun yarns for harp-based fog water harvesting

Fog water harvesting offers a solution to water scarcity. Here, we introduce a method to enhance fog water harvesting systems utilizing electrospun yarns featuring a wettability gradient. These yarns, made from polyvinylidene fluoride (PVDF) and titanium dioxide (TiO₂), gain photoinduced hydrophilicity under UV light due to TiO₂ photocatalytic properties, allowing dynamic shifts from hydrophobic to hydrophilic states. Experiments show that an alternating PVDF-TiO₂ harp with a wettability gradient surpasses purely hydrophobic or hydrophilic versions in fog collection. The strategic mix of hydrophobic and hydrophilic sections enhances droplet movement and water capture, achieving a 16% increase in collection rate up to 400 mg cm⁻² h⁻¹. This approach introduces a novel method for creating wettability gradients in electrospun yarns via UV irradiation and represents a significant advancement in adaptable fog water harvesting systems.