Interstitium‐Mimicking Porous Alveolar Membranes Enable Physiologic Aerosol Transport and Distinct Acute‐Chronic Lung Injury Responses

Barrier membranes govern transport and mechanochemical coupling in lung‐on‐chip systems but typically exhibit low open porosity, limited pore interconnectivity, and diffusion distances exceeding native thin septal regions. An interstitium‐mimicking, alveolus‐shaped poly(ε‐caprolactone) membrane is developed using dual‐templated nonsolvent‐induced phase separation followed by controlled enzymatic pore enlargement. The resulting architecture achieves ∼40% total porosity with 97% pore interconnectivity and a locally thinned dome region (∼2.5 µm). This structure sustains cyclic deformation while increasing oxygen diffusivity fivefold compared with conventional Transwell membranes under acellular and epithelial‐endothelial co‐culture conditions. Integrated into an air‐liquid interface platform, the membrane enables aerosol deposition and quantitative interrogation of cross‐barrier mass transfer. Using carbonaceous nanoscale particulate matter as a model aerosol, controlled exposure induces dose‐dependent oxidative, inflammatory, and genotoxic responses. Matched cumulative dose studies reveal distinct biological trajectories: acute high‐dose exposure produces rapid cytotoxic stress and barrier disruption, whereas chronic low‐dose exposure preserves viability yet promotes sustained DNA repair and genome‐maintenance programs. Compartment‐resolved analysis and therapeutic intervention demonstrate the platform's utility for spatial and translational interrogation of lung injury. By restoring physiologically relevant diffusion distance, interconnectivity, and strain responsiveness, the interstitium‐mimicking membrane advances lung‐on‐chip design toward functional replication of alveolar transport dynamics for studying lung injury and barrier dysfunction.