Multi-material Fabrication for Biodegradable Structures: Enabling the printing of porous mycelium composite structures

Our awareness of the earth's depleting resources has directed focus towards
biomaterials, which can be extracted sustainably and biodegraded after use.
Current fabrication of biomaterial structures is still restricted in strength and
geometry, limiting its use in construction. This paper presents a novel two-phase
multi-material fabrication process to create mycelium composite structures of
higher porosity and complexity with speculated improvements in strength. First,
cellulose pulp inoculated with mycelium is extruded. Then, each layer is filled by
a secondary supporting material. This material, in the form of a gravel- and
sand-slurry, acts as an inhospitable medium steering mycelial growth,
additionally improving aeration to produce stronger structures. After an
intermediate growth period, the secondary material, reusable in a closed-loop
production model, is removed to reveal the fully-grown mycelium structure. The
paper reports on each of the three aspects: the fabrication process, material
experimentation of primary and secondary substrates, as well as geometry of
varying porosity and performance.