Additional data: From Biotechnological Residues to Biodegradable Printed Circuit Boards: Aspergillus niger Mycelium as a Structural Support Material

The electronics industry urgently seeks sustainable, biodegradable alternatives to conventional substrates for printed circuit boards (PCBs) to reduce the environmental impact of electronic waste and CO2 emissions. Here, we introduce a biobased, plastic-like material derived from Aspergillus niger mycelium, AnimatRT. This material is produced from residual biomass generated in industrial citric acid production, offering a circular-economy approach. The raw mycelial biomass, consisting of spherical pellets, is processed via mold casting and air-drying, consolidating the pellets into a dense, plastic-like monolith (1.23 g cm⁻³). When formed into sheets, AnimatRT serves as a viable substrate for low-complexity PCB fabrication, allowing for direct ink writing and manual soldering of electronic components. Although its electrical properties are lower than those of FR-2 (flame retardant 2), a common, low-cost PCB laminate made of paper bonded with a phenolic resin, it remains suitable for low-frequency and proof-of-concept applications and, on average, has 56% lower embodied carbon. The mycelium boards disintegrate in water, allowing recovery of operative electronic components, whose functionality was demonstrated by re-soldering them onto a conventional PCB. The material exhibits high mechanical performance, with compressive strengths of up to 121 MPa, a flexural modulus of 2.3 GPa, and a flexural strength of 30 MPa. It is fully biodegradable (ISO 20200), redispersible in water, has low flammability, and favorable thermal insulation properties (0.21 W (mK)‑1). Heat treatment at 120°C enhances the mechanical properties, improves water resistance, and slows biodegradation. This study demonstrates the first use of biotechnology–derived A. niger mycelium as a biodegradable substrate for PCBs, addressing circularity and end-of-life challenges in electronics.