Material-extrusion additive manufacturing of biodegradable, mechanics-driven reinforcement topologies on cellulose and fungal mycelium membranes

Abstract

This study explores the material effects of mechanics-driven reinforcement topologies on fully compostable membranes made from fungal mycelium or recycled cellulose tissue using material extrusion. Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) was additively printed as defined diamond and re-entrant lattice structures onto compliant substrates. The systematic Make–Break–Simulate approach combines fabrication, tensile testing, simplified mechanical modelling and Life Cycle Assessment (LCA).

Additive reinforcement significantly increased ultimate tensile strength and Young’s modulus in all configurations. Cellulose-based hybrids showed higher stiffness and ultimate tensile load than mycelium systems, indicating more efficient stress transfer due to substrate homogeneity. Diamond lattices exhibited stretching-dominated behavior with axial load amplification, whereas re-entrant lattices produced geometry-induced stiffening and progressive fracture. The re-entrant topology consistently achieved the highest stiffness values and enabled distributed fracture behaviour through geometric stress redistribution.

The screening-level LCA further showed that the mechanical gains of re-entrant reinforcement exceeded the corresponding increase in global warming potential (GWP).

The findings demonstrate that mechanical properties of bio-based membranes can be tuned through geometric pattern design without altering the biological substrate. Topology-controlled additive reinforcement thus offers a scalable strategy to enhance structural reliability while preserving full compostability and material circularity. The presented approach further highlights the potential of geometry-controlled reinforcement as a design strategy for lightweight biodesign and membrane-based applications.