Reactive fungal wearable
Andrew Adamatzky, Anna Nikolaidou, Antoni Gandia, Alessandro Chiolerio, Mohammad Mahdi Dehshib
RReactive fungal wearable
Andrew Adamatzky a,1 , Anna Nikolaidou a,c , Antoni Gandia b , Alessandro Chiolerio a,d , Mohammad MahdiDehshibi a,e a Unconventional Computing Laboratory, UWE, Bristol, UK b Mogu S.r.l., Inarzo, Italy c Department of Architecture, UWE, Bristol, UK d Center for Sustainable Future Technologies, Istituto Italiano di Tecnologia, Torino, Italy e Department of Computer Science, Universitat Oberta de Catalunya, Barcelona, Spain
Abstract
Smart wearables sense and process information from the user’s body and environment and report results oftheir analysis as electrical signals. Conventional electronic sensors and controllers are commonly, sometimesaugmented by recent advances in soft electronics. Organic electronics and bioelectronics, especially with livingsubstrates, offer a great opportunity to incorporate parallel sensing and information processing capabilities ofnatural systems into future and emerging wearables. Nowadays fungi are emerging as a promising candidateto produce sustainable textiles to be used as ecofriendly biowearables. To assess the sensing potential offungal wearables we undertook laboratory experiments on electrical response of a hemp fabric colonised byoyster fungi
Pleurotus ostreatus to mechanical stretching and stimulation with attractants and repellents. Wehave shown that it is possible to discern a nature of stimuli from the fungi electrical responses. The resultspaved a way towards future design of intelligent sensing patches to be used in reactive fungal wearables.
Keywords:
Fungi, Wearables, Biosensing, Unconventional computing
1. Introduction
Smart wearables are devices that extend the functionality of clothes and gadgets, they are responsive tothe wearer and can act as an interface between the wearer and the environment producing a user respon-sive symbiotic system. The smart wearables have been developed as a result of the convergence betweentextiles and electronics (e-textiles). They integrate a high level of technology to provide complex functionsand an easy operation and maintenance [1]. They can be divided into three subgroups: (1) passive smartwearables: able to sense the environment/user, (2) active or reactive smart wearables: able to sense theenvironment/user, and react performing some actions, therefore integrating an actuator, (3) advanced smartwearables: able to sense, react and adapt their behaviour to given circumstances. Sensors provide means todetect signals, actuators react upon stimuli either autonomously or after commands received from a centralprocessing unit [2]. Textile-embedded sensing systems have been developed and commercially exploited inboth the biomedical and safety communities [3]. Smart wearables have been used to record electrocardiogra-phy signals [4], electromyography signals [5], electroencephalography signals [6], temperature [7], biophotonicsensing [8], movement [9], oxygen content, salinity, moisture, or contaminants [10, 11]. Active functionali-ties might include power generation or storage capabilities [12], machine to human interface elements [13],radio frequency communication capabilities [14]. Wearable intelligent systems, intrinsically soft and bettercompliant with extension, deformation and skin stiffness have been developed since a long time [15].The electronic wearables cannot self-grow and self-repair. This deficiency limits their application in thefield of soft robotics and self-growing robots [16, 17, 18, 19]. We can overcome these limits by incorporatingliving fabric in the smart wearables. One of the solutions, explored by us previously, would be to grow slimemould
P. polycephalum on a surface of the cloths or a body of a robot [20]. The slime mould is proven to be abiosensor for the chemical, mechanical and optical stimuli [21, 22, 23]. Despite the sufficient sensorial abilities,the slime mould is rather fragile, highly dependent on environmental conditions and requires particular sourcesof nutrients.Fungi could, however, make a feasible alternative to the slime mould. Fungal materials — grow substratescolonised with mycelium of filamentous fungi — are emerging to be robust, reliable and ecologically friendly
Preprint submitted to Journal Name September 15, 2020 a r X i v : . [ c s . ET ] S e p eplacement for conventional building materials and fabrics [24, 25, 26, 27, 28, 29, 30, 31, 32, 33]. Fungi“possess almost all the senses used by humans” [34]. Fungi sense light, chemicals, gases, gravity and electricfields. Fungi show a pronounced response to changes in a substrate pH [35], mechanical stimulation [36],toxic metals [37], CO [38], stress hormones [39]. Thus, wearables made of or incorporating fabric colonisedby fungi might act as a large distributed sensorial network. Fungi is known to respond to chemical andphysical stimuli by changing patterns of its electrical activity [40, 41, 42] and electrical properties [43]. Thisfeature would allow to interface fungal wearables with conventional electronics. In view of their extension andinterconnectivity, fungal networks represent certainly a sustainable infrastructure-forming substrate, able towire loci separated by considerable space. Moreover, there are indications that mycelium networks not justsense the external stimuli but also process information, and that there is feasible opportunity to convert fungalresponses into Boolean circuits, thus making fungal wearables parallel biological processing networks [44].Previously conducted experiments on sensorial properties of fungi have been using experimental laboratorysetups where substrates colonised by fungi have been kept in ‘comfortable’ conditions of closed containerswith preserved humidity [45]. To assess the feasibility of a fungal wearable prototype in the real world weconducted experiments with a thin hemp-mycelium composite fabric incorporated on a t-shirt wore by amannequin.The paper is structured as follows. We introduce experimental techniques in Sect. 2. Section 3 analysesthe fungal response to stimulation with chemo-attractants, chemo-repellents and mechanical stretching. InSect. 4 we talk about mechanisms of the fungal wearable response and propose directions for further studies.
2. Methods
A commercial strain of the fungus
P. ostreatus (Mogu’s collection code 21-18) was cultured on a hempbedding substrate in plastic boxes c. 35 ×
20 c m in darkness at ambient room temperature c. 22 o C.A hemp substrate well colonised by the fungus was spread on rectangular fragments, c. 12 ×
12 cm ,of moisturised hemp fabric. When the fragments were colonised, as visualised by white mycelial growth onsurface, they were used for experiments. The colonised fabric was attached to a cloth, which in turn wasplaced on a mannequin (Fig. 1(a)). The mannequin was covered by a plastic sheet to prevent a quick decreaseof moisture in the fungal fabric. The fabric was sprayed with distilled water once per two days. The humidityof the fungal fabric was 70%-80% (MerlinLaser Protimeter, UK). The experiments were conducted in a roomwith ambient temperature 21 o C and illumination 30-150 LUX (ISO-Tech ILM 1332A).Electrical activity of the colonised fabric was recorded using pairs of iridium-coated stainless steel sub-dermal needle electrodes (Spes Medica S.r.l., Italy), with twisted cables and ADC-24 (Pico Technology, UK)high-resolution data logger with a 24-bit A/D converter, galvanic isolation and software-selectable samplerates all contribute to a superior noise-free resolution. To keep electrodes stable we have been placing apolyurethane pad under the fabric. The pairs of electrodes were pierced through the fabric and into thepolyurethane pad (Figs 1(b) and 1(c)). We recorded electrical activity one sample per second, where theminimum and maximum logging times were 60.04 and 93.45 hours, respectively. During the recording, thelogger has been doing as many measurements as possible (typically up to 600 per second) and saving theaverage value. We set the acquisition voltage range to 156 mV with an offset accuracy of 9 µ V at 1 Hz tomaintain a gain error of 0.1%. Each electrode pair was considered independently with the noise-free resolutionof 17 bits and conversion time of 60 ms. Each pair of electrodes, further called a Channel (Ch), reporteda difference of the electrical potential between the electrodes. Distance between electrodes was 1-2 cm. Ineach trial, we recorded 5–8 electrode pairs (Ch) simultaneously. We stimulated the fungus with 96% ethanol,malt extract powder (Sigma Aldrich, UK) dissolved in distilled water, dextrose (Ritchie Products Ltd, UK)and by attaching weights (using foldback clips) to the hemp pads.
3. Results
A response of the fungal wearable to a chemo-attractant was studied using malt extract and dextrose. Anexemplar response to application of malt extract is shown in Fig. 2(a). The immediate, first 3 hr, response ismanifested in the spikes up to 15 mV and duration up to 140 min, and is due to a sudden increase in humidityof the substrate. Further response is attributed to fungi sensing malt extract as a chemo-attractant and asource of nutrients. The onset of the response is characterised by low frequency trains of spikes (Fig. 2(b)).2 a)(b) (c)Figure 1: Experimental setup. (a) Overall view of the experimental setup. (b) Close up of the fungal wearable incorporatedinto real cloth. (c) Exemplar locations of electrodes. P o t e n ti a l , m V − × × × × × (a) P o t e n ti a l , m V × × × × × × (b) P o t e n ti a l , m V × × × (c) * P o t e n ti a l , m V × × × × × × × (d) Ch5 P o t e n ti a l , m V − − − −
50 Time, sec1.0984 × × (e) Ch11Ch7 Ch1Ch3 Ch13 P o t e n ti a l , m V − − × × (f)Figure 2: (a) Response to application of malt extract. The moment of malt extract application is shown by asterisk. (b) Lowfrequency trains of spikes. (c) High frequency trains of spikes. (d) Response to application of dextrose. The moment of maltextract application is shown by asterisk. (ef) Response to stimulation with ethanol. An overall response is shown in (e) withsome channels zoomed in (f). h1Ch3Ch5Ch7Ch13 P o t e n ti a l , m V − −
202 Time, sec2.580 × × × (a) P o t e n ti a l , m V (b) P o t e n ti a l , m V − − × × × (c) P o t e n ti a l , m V −
505 Time, sec1.644 × × (d)Figure 3: Fungal wearable’s response to stretching. (a) An exemplar response to stretching of the fabric by attaching 50 g weightto it. (b) Response to removal of 200 g weight recorded from five pairs of differential electrodes. (c) An exemplar response toremoval of the weight recorded on one pair of differential electrodes. (d) Typical response to removal of 200 g weight, recordedon a one pair of differential electrodes. There are 3-4 spikes, with amplitude over 2 mV, in each train. Average distance between spikes in eachtrain is 291 sec, σ = 90, average spike width is 273 sec, σ = 110, average spike amplitude 2.6 mV, σ = 0 . σ = 3, a distance is up to one hour. Typically, a frequency of spiketrains increases with time, a distance between trains decreases to 15 min in average, σ =5 (Fig. 2(c)). Averageamplitude of spike trains is 4.6 mV, σ =2.5.Results of experiments with malt extract echo in the experiments with application of dextrose (Fig. 2(d)).The fungi show low frequency oscillatory activity before stimulation: average distance between spikes is197 min, σ = 13 .
9, average amplitude 0.3 mV, σ = 0 .
2. In first 5 hours after the dextrose application thefrequency of spikes substantially increases: average distance between spikes becomes 22 min, σ = 13 andamplitude increases to average 0.43 mV, σ = 0 .
27. In next 5 hours average amplitude of spikes increases to1.3 mV, σ = 0 .
35, and distance between spikes 20 min, σ = 7.To assess a response to chemo-attractants we used ethanol. We applied 1 ml of 96 % ethanol on thecolonised fabric near loci of Ch5. The response on one of the channel close to the application loci is shown inFig. 2(e). We observed a drop by nearly 8 mV followed by further drop of the electrical potential by nearly8 mV. The time to the peak of the response is c. 7 sec. The drop in potential followed by repolarisationphase, which lasted c. 14 sec. The potential remained c. 11 mV lower than that before stimulation. Theresponse on channels further from the application loci is less pronounced, as seen in Fig. 2(f). The spikes ofelectrical potential recorded on the channels have the following amplitudes: 0.65 mV on Ch1, 0.34 mV onCh3, 0.31 mV on Ch7, 0.5 mV on Ch11, and 0.3 mV on Ch13, where Ch1 is the closest to the applicationloci and Ch13 is the farthest one.To uncover the fungal wearable’s response to stretching we attached 50 g and 200 g weights to the bottompart of the fabric colonised by the fungus. A typical response to the application of 50 g weight is shownin Fig. 3(a)). The response duration is 97 sec in average, σ =37 sec with average response amplitudes is1.3 mV, σ =0.74 mV. Differential electrode pairs, labelled as channels in Fig. 3(a) have been arranged in a5ine from the top to the bottom (Fig. 1(c)), with Ch1 being closest to the top of the fabric and Ch13 tothe bottom part. Most of the response spikes show action potential like depolarisation, repolarisation andhyperpolarisation phases. Ch1 and Ch13 show hyperpolarisation phases set up at higher, compared to thatbefore stimulation, base potential.On application of 200 g weight to lower part of the fabric, variety of response from differential electrodespairs have been recorded. An exemplar response is shown in Fig. 3(b). The response has an average duration38 min, σ =2 min, and average amplitude 1.56 mV, σ =1.24 mV. The response in the example consists of twotrains of high (‘high’ in the frameworks of fungal temporal activity) frequency spikes. Average spike width is80 sec ( σ = 50), average amplitude 0.31 mV ( σ =0.32), average distance between spike in each train is 71 sec( σ =47 sec).Overall reaction to the removal of the stretching stimuli is in the drift of the base potentials on electrodestowards zero, e.g. in Fig. 3(c) we see that the average based potential is -1.17 mV, σ =2 mV, before stimulationwas removed, and -0.8 mV, σ =1.3 mV, after the weight was removed. A typical response, to removal of 200 g,recorded on a single Ch is shown in Fig. 3(d)). The spike there has a duration of 9 sec and amplitude 11 mV.
4. Discussion
We demonstrated that a fabric colonised by the fungus
P. ostreatus shows distinctive sets of responses tochemical and mechanical stimulation. The response to 50 g load, Fig. 3(a), is in the range of c. 1.5 min whichmight indicate that rather purely electro-mechanical events take place than reactions involving propagationof calcium waves [46]. A difference d between timing of the response spikes peaks at the electrodes pairs inthe line is as follows: d (Ch1, Ch3)=3.6 sec, d (Ch1, Ch5)=20 sec, d (Ch1, Ch7)=16 sec, d (Ch1, Ch13)=3 sec.This might indicate that the mycelium networks closer to the fixed end (Ch1) and the end where the load isattached (Ch13) react to the stretching first, the reaction then propagates further into the interior parts ofthe fabric, thus delayed reactions are recorded on the channels Ch5 and Ch7.The response to stimulation with ethanol is in a range of 7 sec. This would rather indicate physico-chemical damages to hyphae walls and corresponding electrical responses. Would amplitude of a responsespike reflect a distance to the stimulation loci? As seen in Fig. 2(f), on most channel the response amplitudesslightly decrease with increasing distance to the stimulation loci however more studies are required to give acertain answer. The response on the channels remote to the stimulation loci happens at the same time, as onthe channel in proximity of the stimulation loci. This indicates that the response might be purely electrical(due to damage to cell walls impulse) and not due to diffusion in the fabric or volatile ethanol.The increase of frequency of electrical potential oscillation in a response to application of chemo-attractantsor nutrients is consistent with previous studies, where intracellular electrical potential of stimulated fungi wasmeasured [40]. Even if in the case of malt extract solution increased spiking could be attributed to a waterthe experiments with dextrose, which was applied dry, show that the spiking shown increased frequency, andoften amplitude, due to reaction to a chemoattractant or nutrient. The increase in amplitude of spikingfive hours after the application of malt or dextrose might be due to the fungus ingesting the nutrients andtransposing them across the wide mycelial network.In laboratory conditions the fungal wearables survived for several months being kept in high humidityconditions. When considering the fungal wearables being used in the every day life measures should be takento preserved the moisture. For example, the fragments of fungal materials can be coated with a breathableplastic.In laboratory conditions the fungal wearables survive for several months being kept in high humidityconditions. For practical future applications of the fungal wearables, preserving the moisture is fundamental.For example, the fragments of fungal materials could be coated with a breathable plastic.Future developments in the field of fungal wearables may be along the following directions.First direction is a computational one. We demonstrate in computational models that a fungal colonycan implement a range of Boolean function [44]. It might be possible to implement an experimental mappingbetween a set of stimuli and distribution of Boolean gates implemented by fungal wearables, as we demon-strated on sensing and computing organic liquid skin [47]. In other words, in a response to a particularstimuli the fungal wearable will generate a unique set of Boolean function.Second direction is in development of a large scale fabric made purely from mycelium — fungal skin(Fig. 4) and tailoring the fabric into wearables. Such mycelial tissue can be prepared using trimitic polypore6 a) (b)(c) (d)Figure 4: Example of fungal flexible materials grown by Mogu S.rl. and branded as PURA Flex ™ . (a) Harvesting of a fungalskin, (b) size comparison with a human being, (c) texture detail resembling animal skin and (d) backpack prototype made withPURA Flex ™ material. a) (b)Figure 5: (a) Part of the hemp glove colonised by fungus is visible in reflected light. (b) Stands of hyphae on the hemp fabric. fungal cultures, which are apparently preferred for the production of sturdy fungal skins, such as fungalleather or mycoleather [33]. More specifically, a fungal fabric can be prepared by pouring a homogenisedslurry of a liquid culture of Ganoderma resinaceum into a static fermentation tray and incubated for twoweeks to allow the fungal hyphae to intermesh, forming a floating mat or skin [42]. Examples of such typeof fungal fabrics are shown in Fig. 4.Third direction would be to culture fungi directly onto the pieces of clothing (Fig. 5(a)). This will allowus to achieve full response cloths and garments.Fourth direction in the development of fungal wearables could be in using fungal hyphae (Fig. 5(b)) aswires and programmable (with e.g. light) resistor or electrically activated resistive switching devices in hybridarchitectures incorporating conventional flexible electronics [48] and live fungi. Routing the direction of thefungal wires can be done by arranging sources of attractants and repellents. Isolation of fungal wires, aswell as localized connections when ordered arrays like the cross-bar array arrangement are required, couldbe done using inorganic materials, such as metal oxides of the proper work function deposited by means ofatomic layer deposition [49], or digitally printed over a large scale, also in case of uneven surfaces [50].
Acknowledgement
This project has received funding from the European Union’s Horizon 2020 research and innovationprogramme FET OPEN “Challenging current thinking” under grant agreement No 858132.
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