Gradient-Janus Wires for Simultaneous Fogwater Harvesting and Electricity Generation

A Gradient-Janus wire (GJW) with a diameter of 0.3 mm has been fabricated on a large scale through liquid confined modification, enabling the opposite conical wetting phenomenon along the same orientation of the GJW, characterized by an increasing superhydrophilic region and a decreasing hydrophobic region. This property allows the GJW to exhibit controllable water hovering, transport, and pinning during fog harvesting, i.e., at a large tilting angle α of 60° (mass increased with decreased α), the GJW can hover 0.6 mg of harvested fogwater in 30 s, can transport 3 mg of fogwater along the gradient in 30 s at α = 4° (with maximal mass reaching up to 4.3 mg at α = −10°), and finally, pin the water droplet at the end of the GJW. Such ability generates an effective torque that serves as the driving force for rotation. We designed a GJWs-wheel by radially arranging 60 GJWs together, resulting in an extremely lightweight structure weighing only 1.9 g. The cumulative torque generated during fog harvesting activates the rotation of the GJWs-wheel. When loaded with a coil within a magnetic field, electricity is generated as output power peaks at around 0.25 μW while maintaining a high water harvesting efficiency averaging approximately 38 ± 2.12 mg/min. This finding is significant as it provides valuable insights into designing materials capable of efficiently harnessing both energy and water resources.