Asymmetric Porous and Wettable Membrane Fabricated by Single‐Step Electrospinning for Thermally Comfortable Wearable Sweat Sensor

Existing multi‐layered Janus structure for wearable sweat sensors complicates the fabrication process and often introduces interfacial barriers that hinder fluid transport. Here, we designed a binary fibrous membrane composed of penetrated hydrophobic polyvinylidene fluoride (PVDF)@hexagonal boron nitride ( h ‐BN) and hydrophilic polyacrylonitrile (PAN) fibers through a single‐step electrospinning process. By dynamically adjusting electrospinning parameters and component ratios, we create an asymmetric structure with a pore‐size gradient and wettability, which facilitates rapid and directional sweat transport without the need for multilayer assembly. The resulting PVDF@h‐BN/PAN membrane demonstrates high sensing performance for key biomarkers, detecting glucose in the range of 0.05–1 m m and lactate from 2.5 m m to 25 m m , with sensitivities of 2.16 µA mM −1 cm −2 and 0.79 µA mM −1 cm −2 , respectively. Furthermore, the incorporation of h ‐BN provides outstanding thermal management, characterized by a solar reflectance of 95.7% and a thermal conductivity of 1.147 W m −1 K −1 , which collectively enable sub‐ambient cooling of up to 6°C under outdoor conditions. The membrane also exhibits excellent flexibility, mechanical robustness, and biocompatibility, ensuring comfort and safety during prolonged wear. This work offers a scalable and integrated material strategy for next‐generation wearable biosensors that combine efficient sweat transport, precise biochemical detection, and passive thermal regulation in a single platform.