Self-grown mycelium in confined geometries as nanofluidic devices.

Precise control of ion and molecular transport at the nanoscale underpins next-generation nanofluidic technologies. However, current approaches such as top-down fabrication and bottom-up assembly remain constrained by cost, scalability, or limited programmability. Fungal mycelium-the largest natural ion transport network in soil-offers a living bio-derived route to nanofluidics. Here, we harness mycelium's self-growth and hyphal anastomosis to construct nanofluidic structures that autonomously conform to confined geometries. With interconnected fibrous networks, nanoscale porosity, and negatively charged surfaces (-2.8 to -4.1 mC m-2), multispecies mycelium generates in situ adaptive pathways through channels, gaps, and open volumes. Specifically, a mycelium-integrated microchannel achieves a pH-gating switch ratio of up to 3.0 and a 55-fold enrichment for dilute cation detection. These results establish the principle that nanofluidic functionality can be biologically grown rather than fabricated, introducing a scalable, sustainable, and geometrically adaptable platform. By bypassing lithography and energy-intensive processing, this bio-derived strategy may enable living and self-organizing ion transport networks with potential applications in sensing, ionic computing, and energy conversion.