Three-Dimensional Printing of Mycelium Hydrogels into Complex Living Materials

Biological materials constantly adapt to their environment, display low embodied energy, and possess remarkable mechanical properties granted by their hierarchical structures. Adapting these principles to human-made objects promises to disrupt the way we engineer our high-performance critical structures. However, today’s engineering materials remain lifeless, and show only limited abilities to adapt and reinforce under load, or to heal and repair in response to damage. Here we harness the livingness of fungal mycelium to reach emerging properties of complex adaptive systems in an engineering context. The potential of the resulting complex material is illustrated by 3D printing living functional skins. We show that fully biobased material is able to autonomously self-heal, self-regenerate and adapt its growth depending on the availability of nutrients in the environment. The adaptive nature of the living mycelium imbues the functional skin thus far inexistent in conventional synthetic materials. To create the animate complex material, we 3D print grid-like structures that provide a mechanically robust architecture combining open airways and a nutrient-rich environment for mycelial growth. The grid is printed using a granulated hydrogel ink that consist of a gelled culture medium inoculated with the fungus. The shaping freedom of the 3D printing process allows us to generate geometries that fulfill specific engineering requirements, such as the encapsulation of robotic parts with a living protective skin. The nutrient concentration in the grid is tuned such that the living mycelium features a balanced growth strategy that combines exploration and exploitation of its surrounding environment. In addition to this decision-making feature, the resulting living material presents several of the hallmarks of complex adaptive systems, such as the emergent behavior of decentralized cells, the efficient processing of information via a scale-free network, the dissipative self-organization processes that promote growth and the organization of building blocks over multiple length scales. This ultimately leads to self-healing, self-regeneration and adaptive properties that are chemically fueled by nutrients in the absence of human intervention.