Polydopamine (PDA) has emerged as a uniquely versatile, biomimetic polymer with profound implications for environmental, biomedical, and energy applications. However, traditional substrate-dependent deposition methods often obscure its intrinsic supramolecular ordering and limit the fabrication of free-standing architectures. This talk highlights recent breakthroughs in harnessing the air-water interface for the bottom-up synthesis of highly oriented, nanometric PDA thin films. By carefully controlling intermolecular interactions at the gas-liquid boundary, we demonstrate the formation of PDA films with a unique 2D-like layered structure, driven by ordered eumelanin-like protomolecule stacking.

Crucially, this interfacial self-assembly enables extraordinary physical properties that surpass those of conventional PDA coatings. Nanoindentation studies reveal superior mechanical resilience in these films—exhibiting a Young’s modulus of 13 ± 4 GPa and a hardness of 0.21 ± 0.03 GPa—allowing these ultrathin layers to be easily transferred to diverse substrates or utilised as robust, free-standing membranes. Furthermore, we will explore the multi-responsive nature of these polycatecholamine nanomembranes, showcasing their capacity for rapid, reversible mechanical actuation triggered by light irradiation, thermal variations, and atmospheric moisture.

The combination of exceptional mechanical robustness, tunable supramolecular ordering, and stimulus-responsiveness establishes air-water interface-derived PDA thin films as a highly scalable and versatile platform. By connecting fundamental structural analysis with practical utility, this presentation will outline how these free-standing films can be integrated into next-generation technologies, with a focus on advanced electrochemical sensors, energy harvesting, actuators and more.