One-step fabrication of a porous hBN/PDMS composite membrane for breathable and thermally dissipative skin-interface applications

Skin-interfaced materials for wearable applications must simultaneously provide effective thermal management, breathability, and mechanical conformability, yet conventional approaches often sacrifice thermal performance for breathability. Here, we report a simple, one-step strategy for the fabrication of a porous hexagonal boron nitride (hBN)/polydimethylsiloxane (PDMS) membrane using perfluorohexane (PFH) as a volatile porogen. This approach directly produces a stable porous architecture during casting and curing, eliminating the need for washing, solvent extraction, or post-fabrication treatment. The pore size is tuned based on the curing temperature, which controls the kinetic competition between matrix curing and PFH volatilization. The overall porosity rises from about 15% to 31% with an increase in the PFH content. Importantly, this porous membrane overcomes the conventional trade-off between thermal conductivity and breathability. Although air voids are present, the membrane achieves a thermal conductivity of 0.22 W/m·K, which is comparable to that of the dense form of the composite. This is because the hBN nanoplatelets assemble along the pore walls, forming continuous heat-conduction pathways. Computational fluid dynamics (CFD) simulations reveal the more effective transfer of heat near the hBN/PDMS composite interface in the porous membrane, which is consistent with the lower heat accumulation observed experimentally. In vivo analysis demonstrates that the porous membrane maintains skin hydration at a stable level of approximately 103–107% and has a mechanical compliance close to that of bare skin, ensuring both physiological and mechanical comfort. These findings establish the proposed one-step fabrication strategy as a material-level foundation for the design of breathable, thermally functional membranes for future skin-interface applications.