Electrical signal transfer characteristics of mycelium-bound composites and fungal fruiting bodies

Abstract

Mycelium-bound composites are normally made of discrete lignocellulosic substrate elements bound together by filamentous fungal hyphae. They can be formed into bespoke components of desired geometries by moulding or extrusion. Mycelium-bound composites with live fungi have been shown to be electrically conductive with memfractive and capacitive attributes. They can be integrated into electrical circuits with nonlinear electrical properties. Advancing fungal electronics, we studied the AC conductive properties of mycelium-bound composites and fungal fruit bodies at higher frequencies across three overlapping bands; 20 Hz to 300 kHz, 10 Hz to 4 MHz and 50 kHz to 3 GHz. Measurements indicate that mycelium-bound composites typically act as low-pass filters with a mean cut-off frequency of ∼500 kHz; with ∼−14 dB/decade roll-off, and mean attenuation across the pass band of $<$1 dB. Fruiting bodies have between one or two orders of magnitude lower mean cut-off frequency (5 kHz–50 kHz depending on species); with −20 dB/decade to −30 dB/decade roll-off, and mean attenuation across the pass band of $<$3 dB. The mechanism for the frequency-dependent attenuation is uncertain; however, the high water content, which is electrically conductive due to dissolved ionisable solids is probably a key factor. The potential for mycelium-bound composites and fruiting bodies in analog computing is explored.