Superwetting, Self-Sterilizing Cu/CuZn-ZnO Grating via Laser Engineering for Advanced Droplet Sensing.

Controlling metal properties is essential for achieving functional applications, as metals show extreme tunability on surface energies, structural surface areas, and sterilization ability. Existing materials for respiratory droplet detection, critical for controlling infectious disease spread, often lack combined extreme wettability and intrinsic antimicrobial activity. Inspired by the photonic crystals of peacock feathers, a highly sensitive and self-sterilizing optical grating sensor is developed based on a core-shell nanostructured copper/copper-zinc and zinc oxide (Cu/CuZn-ZnO) composite (interconnected Cu or CuZn nanoparticles encapsulated by ZnO). A two-step laser-induced process controls the composite's properties, creating hierarchical, core-shell nanostructures and simultaneously tailoring surface energy and morphology for superhydrophilicity. This laser-engineered superwetting surface, combining increased surface area and low surface energy, amplifies aqueous droplet footprint diameter over fivefold, enabling picoliter-range electrical detection. The amounts and distribution of droplets can be analyzed using point-to-point optical Fourier translation analysis and classical statistics. The laser-generated ZnO and residual copper species provide inherent antimicrobial properties, achieving effective self-disinfection. This integrated superhydrophilicity and self-disinfection platform offers significant potential for advanced respiratory droplet analysis and public health monitoring.