Biodegradable 3D‐Printable and Coatable Antifouling Composites for Marine Applications

ABSTRACT The intensive use of conventional, non‐biodegradable plastics in marine environments causes substantial ecological damage. Beyond releasing microplastics and toxic additives, these materials are highly susceptible to biofouling and often rely on biocidal antifoulants, increasing their environmental impact. Here are reported biodegradable antifouling biocomposites that provide tunable shapes and formats via conventional thermoplastic processing, like compression molding and 3D printing, and can be integrated as conformal coatings to retrofit existing structures. The materials pair non‐toxic ingredients: a beeswax matrix, Tween 80 as antifoulant and calcium stearate or stearic acid fillers to tune rheology and improve stability. Tween‐rich formulations demonstrate effective inhibition of Escherichia coli adhesion and, upon seawater immersion, maintain larger unfouled areas than conventional bioplastics. In seawater, the dip‐coated variants adhere efficiently to glass, steel, and plastic substrates. Biochemical oxygen demand in seawater shows biodegradation during 30‐days testing, supporting low persistence. Calcium stearate filler‐reinforced formulations display improved mechanics, endure at least 10 recycling cycles, and can be 3D‐printed into free‐standing architectures. This platform combines structural or coating deployment with effective antifouling, offering potential for underwater applications where complex geometries, integration into existing structures, and minimal impact on fragile ecosystems are critical, such as underwater robotics and coral restoration.