Living co-culture fabrication for biologically crosslinked mycelium-cellulose hydrogels and films

Living materials, owing to their inherent capacities for growth, self-healing, sensing, and adaptation, have attracted widespread attention in recent years. However, controlling growth of living matter to achieve robust and tunable material properties remains a challenge. Here, we report a co-culture strategy that integrates mycelial microfibers with bacterial cellulose nanofibers into hierarchical hydrogels and transparent films. The biological crosslinking between fungal cell wall mannans and cellulose chains yields an interpenetrating micro-nano network with enhanced interfacial hydrogen bonding. As a result, the films achieve simultaneous high tensile strength (195.62 ± 9.06 MPa) and toughness (11.51 ± 0.94 MJ m^-3), surpassing most reported biodegradable films. The micro-nano architecture also enables wide-range optical tunability: haze increases from 16.0% to 78.5% while maintaining approximately 80% transparency by controlling culture duration. Mycelium/bacterial cellulose films with tailored properties are promising candidates for applications such as radiative cooling coatings on outdoor displays. This strategy demonstrates a generalizable principle for programming material structure and properties through microbial activity, offering a green pathway toward next-generation sustainable films for transparent radiative cooling, flexible electronics, and optical devices.