A 3D-printable, general-purpose, sustainable insulator

Insulation materials are everywhere: they keep heat inside buildings, prevent noise from spreading, and protect electrical devices from short circuits. Yet many of the most widely used insulators are petroleum-based foams that persist in the environment after disposal.In this work, we explore a bioinspired alternative based on chito-cellulosic composites (i.e., materials made from chitin and cellulose, the two most abundant biopolymers on Earth). These composites belong to a family known as Fungal-like Adhesive Materials (FLAMs) and can be shaped by casting or additive manufacturing using water-based, biomimetic manufacturing processes.We produced several material variants (using different sources and qualities of cellulose and wood) and benchmarked them with conventional polyurethane foams, the most broadly used insulator. The results show that this new family of insulators, despite its low cost, provides electrical and thermal insulation comparable to that of polyurethane and performs better as an acoustic insulator.Beyond insulation performance, FLAMs offer three decisive advantages. First, they are fire-resistant: although cellulose and wood are combustible on their own, when combined with chitosan the composites become self-extinguishing under the testing conditions. Second, they can be 3D printed, enabling their simultaneous use as an insulator and a structural component. And third, they are fully biodegradable under environmental conditions (i.e., without the need for recovery or management), demonstrating that when buried, the composites lose about 60% of their mass over 40 days, while polyurethane showed negligible change.