Large-scale robotic extrusion-based additive manufacturing with living mycelium materials

Environmental pollution and scarcity of natural resources have led to an increased interest in developing more sustainable materials. Mycelium material fabrication is an emerging bio-based and circular technology to produce materials ranging from foam to particleboard applications. In this process, organic waste streams – such as agricultural waste – are valorised, while biodegradable material is created at the end of its life cycle; a process fitting with the spirit of a circular economy. Up to now, mycelium composites have mostly been grown in moulds, by packing a substrate of lignocellulosic fibres with a fungal strain. This fabrication method restricts not only the size and geometry of the final product, but also the access to oxygen needed for the organism to grow in the centre of the material. Additive manufacturing can potentially overcome those limitations. To establish the groundwork of 3D printing with living mycelium material, this paper provides guidance regarding the technological requirements for 3D-printing fungal material. The purpose is to generate scientific insights on all relevant challenges, processes, production steps by disentangling interdependent process variables ranging from biocompatibility with the living organism, the robotic fabrication system and hardware, the determination of the printing parameter and the sterile printing process to rheological, biological, and geometric properties. Therefore, an extrusion system is developed specifically for robotic printing living biological material. Various manufacturing processes, such as the concentration of ingredients, impact of autoclaving, and time on the viscosity, extrusion pressure, toolpath geometry, the nozzle size, printing speed and mycelium growth, are investigated in detail. These parameters, combined with the rheological and biological behaviour of living material deposition led to the emergence of an experimental fabrication methodology, using a custom robotic manufacturing set-up.