Sustainable UV-shielding sodium alginate films via direct nanostructure replication from cicada wings

The development of environmentally friendly, biodegradable films with functional performance is essential for reducing dependence on petroleum-based polymers and mitigating environmental pollution. In this study, we present a sustainable and straightforward method for producing UV shielding sodium alginate films by directly transferring natural nanostructures from cicada wings onto the film surface through a simple casting process. The nanostructured films were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and ultraviolet visible (UV-Vis) transmission spectroscopy. Replication of the wing nanostructures produced a significant reduction in UV transmittance, attributed to enhanced Rayleigh and Mie scattering. Ionic crosslinking with calcium chloride further altered the surface morphology, increased thermal stability, and modified wettability. Notably, these effects were achieved without the use of petroleum-based polymers, chemical additives, or complex fabrication techniques. This approach demonstrates a viable pathway for developing sustainable, functional biopolymer films with potential applications in packaging, coatings, and biomedical products.