Tortoise beetle-inspired sustainable films with tunable properties based on on-demand embedding and release of functional microspheres

Inspired by tortoise beetle, a novel method for preparing sustainable films, leveraging the on-demand embedding or release behavior of the functional fillers to impart or eliminate functions to the film is reported. The microscopic shape-memory behavior of the film surface was characterized using microscopy techniques and finite-element analysis to investigate the embedding and release of single micro-/nanospheres on the film surface, which were affected by sphere diameters and programming temperatures. By utilizing different functional fillers and distribution densities, the transformation and tunability of film properties such as optical reflection and fluorescence was demonstrated. Different functions of the film were altered through multiple cycles, showcasing the ability to immobilize patterns, step-wise release, recycle materials and create temperature-sensitive anticounterfeiting codes and decoration on objects. This approach offers a promising avenue for developing sustainable films with tunable functions and highlights the potential for recycling functional fillers, contributing to both environmental sustainability and material reusability.