Towards fungal sensing skin

Abstract

A fungal skin is a thin flexible sheet of a living homogeneous mycelium made by a filamentous fungus. The skin could be used in future living architectures of adaptive buildings and as a sensing living skin for soft self-growing/adaptive robots. In experimental laboratory studies we demonstrate that the fungal skin is capable for recognising mechanical and optical stimulation. The skin reacts differently to loading of a weight, removal of the weight, and switching illumination on and off. These are the first experimental evidences that fungal materials can be used not only as mechanical 'skeletons' in architecture and robotics but also as intelligent skins capable for recognition of external stimuli and sensorial fusion.

Keywords: Biomaterials; Fungi; Sensing; Sensorial fusion; Soft robotics.

Fig. 1

Phototropism is one of the leading guiding factors in the formation of basidiocarps in Ganoderma spp.

Fig. 2

Fungal skin response to mechanical and optical stimulation. a Exemplar recording of fungal skin electrical activity under tactile and optical stimulation. Moments of applying and removing a weight are shown as ‘W*’ and ‘Wo’ and switching light ON and OFF as ‘L*’ and ‘Lo’. b Exemplar response to mechanical stimulation. Moments of applying and removing a weight are shown as ‘W*’ and ‘Wo’. High-amplitude response is labelled ‘s’. This response is followed by a train of spikes ‘r’. A response to the removal of the weight is labelled ‘p’. c Exemplar response of fungal skin to illumination, recorded on three pairs of differential electrodes. ‘L*’ indicates illumination is applied, ‘Lo’ illumination is switched off

Fig. 3

a A scheme of the fungal skin responses to mechanical load and optical stimulations. b Slime mould P. polycephalum response to application of 0.01 g glass capillary tube. Redrawn from [30]

Fig. 4

Recording of electrical activity of fungal skin. a Close-up texture detail of a fungal skin. b A photograph of electrodes inserted into the fungal skin. c Train of three low-frequency spikes, average width of spikes there is 1500 s, a distance between spike peaks is 3000 s and average amplitude is 0.2 mV. d Example of several train of high-frequency spikes. Each train $T_{\mathit{xy}}=(A_{\mathit{xy}},W_{\mathit{xy}},P_{\mathit{xy}})$ is characterised by average amplitude of spikes $A_{\mathit{xy}}$ mV, width of spikes $W_{\mathit{xy}}$ sec and average distance between neighbouring spikes’ peaks $P_{\mathit{xy}}$ sec: $T_{\mathit{ab}}=(2.6,245,300)$, $T_{\mathit{cd}}=(1.7,160,220)$, $T_{\mathit{ef}}=(1.6,340,340)$, $T_{\mathit{gh}}=(2.5,240,350)$, $T_{\mathit{ij}}=(2.5,220,590)$, $T_{\mathit{kl}}=(2.6,290,440)$