Experimental study of 3D printed biochar-mycelium composites via liquid deposition modeling for sustainable building components: compatibility, shrinkage control, structural integrity and prefabrication

What if building components could be 3D printed, grown, and welded together by living organisms? 3D printed mycelium-based composites (MBC) offer this potential but are limited by high shrinkage and low mechanical performance. This study pairs biochar, a stable, carbon-sequestering filler not yet tested with mycelium in additive manufacturing, with toolpaths inspired by brain-coral geometry designed to distribute oxygen-rich corridors and material-dense regions across the printed element, to support biological colonization and buildability. Eight empirical experiments address: biochar–mycelium compatibility, relationships between biomimetic toolpaths and bio-mechanical performance, and upscaling via segmented printing and bio-welding. Results show reduced vertical shrinkage (3–5%) under specific conditions, below typical lignocellulosic MBC values. Preliminary compressive tests suggest potential improvement, though sample size limits significance. A larger demonstrator was successfully printed and bio-welded, but dimensional stability still remained inconsistent. Future work will focus on water regulation for dimensional stability and mechanical analysis of gradients.