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Mem-fractive properties of mushrooms
Abstract
Memristors close the loop for I-V characteristics of the traditional, passive, semi-conductor devices. A memristor is a physical realisation of the material implication and thus is a universal logical element. Memristors are getting particular interest in the field of bioelectronics. Electrical properties of living substrates are not binary and there is nearly a continuous transitions from being non-memristive to mem-fractive (exhibiting a combination of passive memory) to ideally memristive. In laboratory experiments we show that living oyster mushrooms Pleurotus ostreatus exhibit mem-fractive properties. We offer a piece-wise polynomial approximation of the I-V behaviour of the oyster mushrooms. We also report spiking activity, oscillations in conduced current of the oyster mushrooms.
... The current-voltage behaviour of the fruit bodies of grey oyster fungi Pleurotus ostreatus was investigated experimentally in [23]. The pinching and the size of hysteresis lobes in the measurement data were compared with the lobes in I-V relation of the ideal memristor. ...
... The pinching and the size of hysteresis lobes in the measurement data were compared with the lobes in I-V relation of the ideal memristor. It was concluded that the fungi' electrical memory behaviour acts as the memfractors between memristors and mem-capacitors [23]. Electrical current responses measured on human skin have shown an increase in the current amplitude from one cycle to another [24]. ...
Recent works show that the plants can exhibit nonlinear memristive behavior when excited with low-frequency signals. However, in the literature, only linear bio-impedance models are extensively considered to model the electrical properties of biological tissues without acknowledging the nonlinear behavior. In this paper, we show with experiments, for the first time, the pinched hysteresis behavior in seven fruits and vegetables including tomato, orange, lemon, aubergine, and kiwi which exhibit single pinch-off point, and others such as carrot and cucumber exhibit double pinch-off points (i.e., three lobes). We also proposed a memristive fractional-order bio-impedance model by extending the Hayden bio-impedance model. The proposed model is used to fit the measurements of the seven fruits and vegetables showing very good matching.
... Memristors hold substantial promise for neuromorphic architectures due to their memory retention and synaptic emulation capabilities, addressing limitations in conventional computing architectures. Its amazing properties made researchers curious to look into nature, where they recently discovered that mushrooms are also memristors [29,30], having the potential to advance the field of hybrid electronic systems. Many efforts are made in developing neuromorphic circuits and AI applications using memristors [31][32][33][34][35][36][37][38][39]. ...
This paper presents a novel approach to in situ memristive learning by training spiking neural networks (SNNs) entirely within the circuit using memristor emulators in SPICE. The circuit models neurons using Lapicque neurons and employs pulse-based spike encoding to simulate spike-timing-dependent plasticity (STDP), a key learning mechanism in SNNs. The Lapicque neuron model operates according to the Leaky Integrate-and-Fire (LIF) model, which is used in this study to model spiking behavior in memristor-based SNNs. More exactly, the first memristor emulator in PySpice, a Python library for circuit simulation, was developed and integrated into a memristive circuit capable of in situ learning, named the “In Situ Memristive Learning Method for Pattern Classification.” This novel technique enables time-based computation, where neurons accumulate incoming spikes and fire once a threshold is reached, mimicking biological neuron behavior. The proposed method was rigorously tested on three diverse datasets: XPUE, a custom non-dominating 3 × 3 image dataset; a 3 × 5 digit dataset ranging from 0 to 5; and a resized 10 × 10 version of the Modified National Institute of Standards and Technology (MNIST) dataset. The neuromorphic circuit achieved successful pattern learning across all three datasets, outperforming comparable results from other in situ training simulations on SPICE. The learning process harnesses the cumulative effect of memristors, enabling the network to learn a representative pattern for each label efficiently. This advancement opens new avenues for neuromorphic computing and paves the way for developing autonomous, adaptable pattern classification neuromorphic circuits.
... These applications encompass the development of logical circuits, stateful logic operations, passive crossbar arrays of memristors for logic operations, memory-aided logic circuits, self-programmable logic circuits, and memory devices. The investigation of mem-fractive characteristics in fungi arises from the possible advantages it presents 35 .If the strands of fungal mycelium present in mycelium bound composites, along with the fruit bodies, have mem-fractive characteristics, it creates opportunities to include different memory and computer devices directly into architectural construction materials made from fungal substrates. In addition, the idea of wearable fungi that may be used as clothing is still in its initial phases but has demonstrated favourable characteristics including a sleek design, great flexibility, and minimal energy usage in comparison to traditional artificial wearable sensory devices 32 . ...
The work introduces a composite material that combines Kombucha cellulose mats with synthetic thermal proteinoids to create electroactive biofilms, capable for sensing and computation. The synthesis of proteinoids involves heating amino acid mixtures, which leads to the formation of proto–cell structures capable of biological electrical signalling. We demonstrate that these hybrid biofilms exhibit adjustable memristive and memfractance properties, which can be utilised for unconventional computing tasks. The potential applications of living biofilms extend beyond neural interfaces, encompassing bioinspired robotics, smart wearables, adaptive biorobotic systems, and other technologies that rely on dynamic bioelectronic materials. The composite films offer a wide range of options for synthesis and performance customisation. Current research is dedicated to customising the composition, nanostructure, and integration of proteinoids in hybrid circuits to achieve specific electronic functionalities. Overall, these cross–kingdom biofilms are an intriguing category of materials that combine the unique properties of biological organisms and smart polymers. The Kombucha–proteinoid composites are a significant step forward in the development of future technologies that bridge the gap between living and artificial life systems. These composites have the remarkable ability to support cellular systems and demonstrate adaptive bioelectronic behaviour.
... We have already demonstrated that we achieved in implementing memristors (Beasley et al., 2022), oscillators , photo-sensors (Beasley et al., 2020), pressure sensors (Adamatzky and Gandia, 2022), chemical sensors and Boolean logical circuits (Roberts and Adamatzky, 2021) with living mycelium networks. Due to nonlinear electric response of fungal tissues, they are ideally suited for transformation of lowfrequency AC signals. ...
We stimulate mycelian networks of oyster fungi Pleurotus ostreatus with low frequency sinusoidal electrical signals. We demonstrate that the fungal networks can discriminate between frequencies in a fuzzy-like or threshold based manner. Details about the mixing of frequencies by the mycelium networks are provided. The results advance the novel field of fungal electronics and pave ground for the design of living, fully recyclable, electron devices.
... The fungal materials are used in acoustic insulation panels ( Pelletier et al., 2013 ;Elsacker et al., 2020 ;Robertson et al., 2020 ), thermal insulation wall cladding ( Wang et al., 2016 ;Yang et al., 2017 ;Xing et al., 2018 ;Girometta et al., 2019 ;Cárdenas-R, 2020 ;Dias et al., 2021 ), packaging materials ( Holt et al., 2012 ;Mojumdar et al., 2021 ;Sivaprasad et al., 2021 ) and wearables ( Karana et al., 2018 ;Silverman et al., 2020 ;Appels, 2020 ;Jones et al., 2021 ;Adamatzky et al., 2021c ). In Adamatzky et al. (2019) , we proposed to develop a structural substrate by using live fungal mycelium, functionalise the substrate with nanoparticles and polymers to make mycelium-based electronics ( Beasley et al., 2020a ;2020b ;2020c ), implement sensorial fusion and decision making in the mycelium networks ( Adamatzky et al., 2020 ). The structural substrate -the mycelium bound composites -will be used to grow monolithic buildings from the functionalised fungal substrate ( Adamatzky et al., 2021a ). ...
Fungal construction materials—substrates colonised by mycelium—are getting increased recognition as viable ecologically friendly alternatives to conventional building materials. A functionality of the constructions made from fungal materials would be enriched if blocks with living mycelium, known for their ability to respond to chemical, optical and tactile stimuli, were inserted. We investigated how large blocks of substrates colonised with mycelium of Ganoderma resinaceum responded to stimulation with heavy weights. We analysed details of the electrical responses to the stimulation with weights and show that ON and OFF stimuli can be discriminated by the living mycelium composites and that a habituation to the stimulation occurs. Novelty of the results in the reporting on changes in electrical spiking activity of mycelium bound composites in response to a heavy loads.
... Fungal electronics can be embedded into fungal materials and wearables or used as stand alone sensing and computing devices. In experimental laboratory conditions we demonstrated that fungi can be used as memristors [7], photosensors [8,3], chemical sensors [14,5], humidity sensors [23], and tactile sensors [3]. To make a functional fungal circuits one must connect several fungal electronic devices. ...
Living fungal mycelium networks are proven to have properties of memristors, capacitors and various sensors. To further progress our designs in fungal electronics we need to evaluate how electrical signals can be propagated through mycelium networks. We investigate the ability of mycelium-bound composites to convey electrical signals, thereby enabling the transmission of frequency-modulated information through mycelium networks. Mycelia were found to reliably transfer signals with a recoverable frequency comparable to the input, in the \SIrange{100}{10000} {\hertz} frequency range. Mycelial adaptive responses, such as tissue repair, may result in fragile connections, however. While the mean amplitude of output signals was not reproducible among replicate experiments exposed to the same input frequency, the variance across groups was highly consistent. Our work is supported by NARX modelling through which an approximate transfer function was derived. These findings advance the state of the art of using mycelium-bound composites in analogue electronics and unconventional computing.
... We have already demonstrated that we achieved in implementing memristors (Beasley et al., 2022), oscillators , photo-sensors (Beasley et al., 2020), pressure sensors (Adamatzky and Gandia, 2022), chemical sensors and Boolean logical circuits (Roberts and Adamatzky, 2021) with living mycelium networks. Due to nonlinear electric response of fungal tissues, they are ideally suited for transformation of lowfrequency AC signals. ...
We stimulate mycelian networks of oyster fungi Pleurotus ostreatus with low frequency sinusoidal electrical signals. We demonstrate that the fungal networks can discriminate between frequencies in a fuzzy or threshold based manner. Details about the mixing of frequencies by the mycelium networks are provided. The results advance the novel field of fungal electronics and pave ground for the design of living, fully recyclable, electronic devices.
... Fungal physiology and behaviour gave rise to a novel field of fungal computing and fungal electronics Adamatzky [2018], Adamatzky et al. [2020a], Beasley et al. [2021]. Whilst experimental laboratory prototyping of fungi-based computing devices is underway it is imperative to establish a wider theoretical background for fungal computing. ...
Cells in a fungal hyphae are separated by internal walls (septa). The septa have tiny pores that allow cytoplasm flowing between cells. Cells can close their septa blocking the flow if they are injured, preventing fluid loss from the rest of filament. This action is achieved by special organelles called Woronin bodies. Using the controllable pores as an inspiration we advance one and two-dimensional cellular automata into Elementary fungal cellular automata (EFCA) and Majority fungal automata (MFA) by adding a concept of Woronin bodies to the cell state transition rules. EFCA is a cellular automaton where the communications between neighboring cells can be blocked by the activation of the Woronin bodies (Wb), allowing or blocking the flow of information (represented by a cytoplasm and chemical elements it carries) between them. We explore a novel version of the fungal automata where the evolution of the system is only affected by the activation of the Wb. We explore two case studies: the Elementary Fungal Cellular Automata (EFCA), which is a direct application of this variant for elementary cellular automata rules, and the Majority Fungal Automata (MFA), which correspond to an application of the Wb to two dimensional automaton with majority rule with Von Neumann neighborhood. By studying the EFCA model, we analyze how the 256 elementary cellular automata rules are affected by the activation of Wb in different modes, increasing the complexity on applied rule in some cases. Also we explore how a consensus over MFA is affected when the continuous flow of information is interrupted due to the activation of Woronin bodies.
... We have already demonstrated that we achieved in implementing memristors [21], oscillators [22], photosensors [23], pressure sensors [24], chemical sensors [25] and Boolean logical circuits [26] with living mycelium networks. Due to nonlinear electric response of fungal tissues, they are ideally suited for transformation of low-frequency AC signals. ...
We stimulate mycelian networks of oyster fungi Pleurotus ostreatus with low frequency sinusoidal electrical signals. We demonstrate that the fungal networks can discriminate between frequencies in a fuzzy or threshold based manner. Details about the mixing of frequencies by the mycelium networks are provided. The results advance the novel field of fungal electronics and pave ground for the design of living, fully recyclable, electron devices.
... Second, we can prototype neuromorphic circuits with kombucha mats. There is a high likelihood of kombucha mats exhibiting memristive properties (similar to memristive properties of slime mould [51] and fungi [52]). The memristive properties would further imply [53,54,55,56] that it is possible to implement learning, memory and construct synaptic connections in the zoogleal mats. ...
A kombucha is a sugared tea fermented by a symbiotic community of over twenty species of bacteria and yeasts. The community produces and inhabits cellulosic gelatinous zoogleal mats. We studied electrical activity of the kombucha mats using pairs of differential electrodes. We discovered that the mats produce action like spikes of electrical potential. The spikes are often grouped in the trains of spikes. Characteristics of the spikes and trains of spikes are presented. We demonstrated that electrical responses of kombucha mats to chemical, electrical and optical stimulation are distinctive and therefore the mats can be used as sensors, or even unconventional computing devices.
... Following this, a successful implementation included the analysis of the electrical properties of fungi belonging to Pleurotus spp. [37], a significant step taken towards building a biological memory-storing device. In a previous study [38], it was shown that fungi are able to record the action of exogenous stimuli as fluctuations in the electrical signalling between distinct members of the same population, in a similar fashion to how information is passed from sensory neurons to the central nervous system and then motor neurons. ...
The engineering of living cells able to learn algorithms by themselves, such as playing board games —a classic challenge for artificial intelligence— will allow complex ecosystems and tissues to be chemically reprogrammed to learn complex decisions. However, current engineered gene circuits encoding decision-making algorithms have failed to implement self-programmability and they require supervised tuning. We show a strategy for engineering gene circuits to rewire themselves by reinforcement learning. We created a scalable general-purpose library of Escherichia coli strains encoding elementary adaptive genetic systems capable of persistently adjusting their relative levels of expression according to their previous behavior. Our strains can learn the mastery of 3×3 board games such as tic-tac-toe, even when starting from a completely ignorant state. We provide a general genetic mechanism for the autonomous learning of decisions in changeable environments.
One-Sentence Summary
We propose a scalable strategy to engineer gene circuits capable of autonomously learning decision-making in complex environments.
... The fungal materials are used in acoustic insulation panels ( Pelletier et al., 2013 ;Elsacker et al., 2020 ;Robertson et al., 2020 ), thermal insulation wall cladding ( Wang et al., 2016 ;Yang et al., 2017 ;Xing et al., 2018 ;Girometta et al., 2019 ;Cárdenas-R, 2020 ;Dias et al., 2021 ), packaging materials ( Holt et al., 2012 ;Mojumdar et al., 2021 ;Sivaprasad et al., 2021 ) and wearables ( Karana et al., 2018 ;Silverman et al., 2020 ;Appels, 2020 ;Jones et al., 2021 ;Adamatzky et al., 2021c ). In Adamatzky et al. (2019) , we proposed to develop a structural substrate by using live fungal mycelium, functionalise the substrate with nanoparticles and polymers to make mycelium-based electronics ( Beasley et al., 2020a ;2020b ;2020c ), implement sensorial fusion and decision making in the mycelium networks ( Adamatzky et al., 2020 ). The structural substrate -the mycelium bound composites -will be used to grow monolithic buildings from the functionalised fungal substrate ( Adamatzky et al., 2021a ). ...
Fungal construction materials—substrates colonised by mycelium—are getting increased recognition as viable ecologically friendly alternatives to conventional building materials. A functionality of the constructions made from fungal materials would be enriched if blocks with living mycelium, known for their ability to respond to chemical, optical and tactile stimuli, were inserted. We investigated how large blocks of substrates colonised with mycelium of Ganoderma resinaceum responded to stimulation with heavy weights. We analysed details of the electrical responses to the stimulation with weights and show that ON and OFF stimuli can be discriminated by the living mycelium composites and that a habituation to the stimulation occurs. Novelty of the results cast in the reporting on changes in electrical spiking activity of mycelium bound composites in response to a heavy loads.
The socio‐economic struggles in Africa are partly attributed to the low productivity of the agricultural sector. The Sustainable Development Goals Centre for Africa (SDGC/A) and the African Development Bank Group (AfDBG) both agree that the continent needs sustainable interventions to boost agricultural productivity, employment, and income. In this regard, mycelium composite production can present one potential solution. The added value to agricultural waste used to produce mycelium composites can generate additional revenue for farmers, serving as an incentive to increase agricultural productivity. Furthermore, the establishment of mycelium composite start‐ups can increase employment and income, especially for women and the youth. Mycelium composites can also aid in mitigating environmental and health challenges caused by some of the current waste management practices in Africa. This review offers valuable insights into the potential use of mycelium composites as a sustainable alternative for Africa. It explores the potential use of locally accessible resources, the potential applications for the composites in Africa, and the potential challenges that may arise with this technology. It further assesses the potential contribution of this technology to sustainable development in Africa in line with the Sustainable Development Goals (SDGs) set by the United Nations (UN).
Living substrates are capable for nontrivial mappings of electrical signals due to the substrate nonlinear electrical characteristics. This property can be used to realise Boolean functions. Input logical values are represented by amplitude or frequency of electrical stimuli. Output logical values are decoded from electrical responses of living substrates. We demonstrate how logical circuits can be implemented in mycelium bound composites. The mycelium bound composites (fungal materials) are getting growing recognition as building, packaging, decoration and clothing materials. Presently the fungal materials are passive. To make the fungal materials adaptive, i.e. sensing and computing, we should embed logical circuits into them. We demonstrate experimental laboratory prototypes of many-input Boolean functions implemented in fungal materials from oyster fungi P. ostreatus. We characterise complexity of the functions discovered via complexity of the space-time configurations of one-dimensional cellular automata governed by the functions. We show that the mycelium bound composites can implement representative functions from all classes of cellular automata complexity including the computationally universal. The results presented will make an impact in the field of unconventional computing, experimental demonstration of purposeful computing with fungi, and in the field of intelligent materials, as the prototypes of computing mycelium bound composites.
Mycelium networks are promising substrates for designing unconventional computing devices providing rich topologies and geometries where signals propagate and interact. Fulfilling our long-term objectives of prototyping electrical analog computers from living mycelium networks, including networks hybridised with nanoparticles, we explore the possibility of implementing Boolean logical gates based on electrical properties of fungal colonies. We converted a 3D image-data stack of Aspergillus niger fungal colony to an Euclidean graph and modelled the colony as resistive and capacitive (RC) networks, where electrical parameters of edges were functions of the edges’ lengths. We found that and, or and and-not gates are implementable in RC networks derived from the geometrical structure of the real fungal colony.
Mycelium-bound composites consist of discrete substrate elements joined together by filamentous hypha strands. These composites can be moulded or extruded into custom components of desired shapes. When live fungi are present these composites exhibit electrical conductivity as well as memfractive and capacitive properties. These composites might be used in nonlinear electrical circuits. We investigated the AC conductive properties of mycelium-bound composites and fungal fruit bodies at higher frequencies, spanning three overlapping frequency ranges: 20 Hz to 300 kHz, 10 Hz to 4 MHz, and 50 kHz to 3 GHz, to advance fungal electronics. Our measurements revealed that mycelium-bound composites primarily function as low-pass filters, with an average cut-off frequency of 500 kHz and a roll-off rate of 14 dB/decade. Within the pass band, the average attenuation is less than 1 dB. Fungal fruiting bodies have significantly lower mean cut-off frequencies that range from 5 Khz to 50 Khz depending on the species. Their roll-off range from to decibels per decade, with mean attenuation across the pass band less than 3 decibels. The precise mechanism underlying frequency-dependent attenuation is unclear. However, the high-water content, which is around 80 % in mycelium-bound composites and up to 92 % in fruiting bodies, is important. Because of the presence of dissolved ionizable solids, this water content is electrically conductive, making it a likely contributing factor. This research looks into the potential applications of mycelium-bound composites and fungal fruiting bodies in analog computing.
Cells in a fungal hyphae are separated by internal walls (septa). The septa have tiny pores that allow cytoplasm flowing between cells. Cells can close their septa blocking the flow if they are injured, preventing fluid loss from the rest of filament. This action is achieved by special organelles called Woronin bodies. Using the controllable pores as an inspiration we advance one and two-dimensional cellular automata into Elementary fungal cellular automata (EFCA) and Majority fungal automata (MFA) by adding a concept of Woronin bodies to the cell state transition rules. EFCA is a cellular automaton where the communications between neighboring cells can be blocked by the activation of the Woronin bodies (Wb), allowing or blocking the flow of information (represented by a cytoplasm and chemical elements it carries) between them. We explore a novel version of the fungal automata where the evolution of the system is only affected by the activation of the Wb. We explore two case studies: the Elementary Fungal Cellular Automata (EFCA), which is a direct application of this variant for elementary cellular automata rules, and the Majority Fungal Automata (MFA), which correspond to an application of the Wb to two dimensional automaton with majority rule with Von Neumann neighborhood. By studying the EFCA model, we analyze how the 256 elementary cellular automata rules are affected by the activation of Wb in different modes, increasing the complexity on applied rule in some cases. Also we explore how a consensus over MFA is affected when the continuous flow of information is interrupted due to the activation of Woronin bodies.
Living fungal mycelium networks are proven to have properties of memristors, capacitors and various sensors. To further progress our designs in fungal electronics we need to evaluate how electrical signals can be propagated through mycelium networks. We investigate the ability of mycelium-bound composites to convey electrical signals, thereby enabling the transmission of frequency-modulated information through mycelium networks. Mycelia were found to reliably transfer signals with a recoverable frequency comparable to the input, in the 100Hz to 10 000Hz frequency range. Mycelial adaptive responses, such as tissue repair, may result in fragile connections, however. While the mean amplitude of output signals was not reproducible among replicate experiments exposed to the same input frequency, the variance across groups was highly consistent. Our work is supported by NARX modelling through which an approximate transfer function was derived. These findings advance the state of the art of using mycelium-bound composites in analogue electronics and unconventional computing.
We demonstrate that zoogleal mats of kombucha exhibit spikes of electrical resistance. A kombucha is a sugared tea fermented by a symbiotic community of over 20 species of bacteria and yeasts which produce cellulosic gelatinous zoogleal mats. We recorded electrical resistance of the zoogleal mats via platinum electrodes placed at a distance 1 cm of each other. We found that the mats show temporal variations in electrical resistance in a range 0.13–0.19[Formula: see text]M[Formula: see text]. We discovered spikes of the mats resistance morphologically similar to action potential spikes. Average duration of a resistance spike is 1.8[Formula: see text]min, average amplitude is 2.2[Formula: see text]k[Formula: see text]. Average interval between resistance spikes is c. 20[Formula: see text]min. The discovered resistive spiking of kombucha mats might indicate on their memfractive properties, and thus, open pathways towards prototyping neuromorphic devices with living zoogleal mats.
In this concept article, we review recent works on the use of biologically-derived materials, including biomolecules, hybrid biomolecular composites, and natural tissues for achieving stimuli-responsiveness, adaptability, and memory storage for potential neuromorphic computing applications. Unlike solid-state materials, bioderived platforms are often intrinsically modular, including possessing the ability to leverage the diversity of naturally multifunctional biomolecules, cornerstones in biological transduction, signaling, and learning. The primary neuromorphic functionality of bioderived systems considered here is memory resistance, as obtained through combinations of resistive switching, activity-dependent plasticity, and memory storage. In some cases, these capabilities are achieved in bio-derived systems by closely emulating the structure, function, or signaling mechanisms found in living neurons. Our review considers bioderived systems that span multiple length scales and levels of hierarchical complexity: from single-molecule enabled devices to intact tissues, interrogated either in vitro or in vivo on living organisms. Through this exercise, we offer our perspective on research opportunities in the development and use of synapse- and neuron-inspired bioderived systems, including the prospect of biocompatible, and even tissue-like, neuromorphic materials to smartly monitor and treat injury and disease, deliver therapeutics, and interpret neural activity. These capabilities could unlock a new generation of smart, adaptable bioderived composites that autonomously report, learn (i.e., classify, forecast), compute, and actuate in the direct vicinity of living cells and tissues, i.e. at the edge of biology.
Living substrates are capable for nontrivial mappings of electrical signals due to the substrate nonlinear electrical characteristics. This property can be used to realise Boolean functions. Input logical values are represented by amplitude or frequency of electrical stimuli. Output logical values are decoded from electrical responses of living substrates. We demonstrate how logical circuits can be implemented in mycelium bound composites. The mycelium bound composites (fungal materials) are getting growing recognition as building, packaging, decoration and clothing materials. Presently the fungal materials are passive. To make the fungal materials adaptive, i.e. sensing and computing, we should embed logical circuits into them. We demonstrate experimental laboratory prototypes of many-input Boolean functions implemented in fungal materials from oyster fungi P. ostreatus. We characterise complexity of the functions discovered via complexity of the space-time configurations of one-dimensional cellular automata governed by the functions. We show that the mycelium bound composites can implement representative functions from all classes of cellular automata complexity including the computationally universal. The results presented will make an impact in the field of unconventional computing, experimental demonstration of purposeful computing with fungi, and in the field of intelligent materials, as the prototypes of computing mycelium bound composites.
Fungal electronics is a family of living electronic devices made of mycelium bound composites or pure mycelium. Fungal electronic devices are capable of changing their impedance and generating spikes of electrical potential in response to external control parameters. Fungal electronics can be embedded into fungal materials and wearables or used as stand alone sensing and computing devices.
The bacterial skin studied here is a several centimeter-wide colony of Acetobacter aceti living on a cellulose-based hydrogel. We demonstrate that the colony exhibits trains of spikes of extracellular electrical potential, with amplitudes of the spikes varying from 1 to 17 mV. The bacterial pad responds to mechanical stimulation with distinctive changes in its electrical activity. While studying the passive electrical properties of the bacterial pad, we found that the pad provides an open-circuit voltage drop (between 7 and 25 mV) and a small short-circuit current (1.5–4 nA). We also observed by pulsed tomography and spatially resolved impedance spectroscopy that the conduction occurs along preferential paths, with the peculiar side-effect of having a higher resistance between closer electrodes. We speculate that the Acetobacter biofilms could be utilized in the development of living skin for soft robots: such skin will act as an electrochemical battery and a reactive tactile sensor. It could even be used for wearable devices.
Recent developments in biotechnology and its integration with material science have given rise to a new set of materials that utilize natural mechanisms to produce constituent matter. These developments are required as the current generation of materials are to be replaced with novel green materials that will not become a source of pollution to our planet. Environmental issues that are caused as a result of non-biodegradability of synthetic plastics, as well as fossil fuel depletion, are the main reasons to pursue alternate materials from natural sources. The paper mainly focuses on the development of mycelium-based bio-composites which makes use of saw dust-coir pith substrate as a potential replacement for expanded polystyrene (EPS) in packaging as well as other applications. Mycelium is a fibrous network of filamentous fungi that is formed on organic materials. Mycelia from the fungi, Pleurotus Ostreatus, feeds and grows on the saw dust-coir pith substrate that is mixed in the ratio 3:2. Mycelium based composites unlike other bio-materials are less expensive and have high production yields. Fabrication of the composite is done by selecting a suitable substrate ratio and the evaluation of the samples is done based on their biodegradability, compressive strength, acoustic performance, thermal conductivity and water absorption properties. All the tests showed promising results for the developed bio-composite and the composite can be earmarked as a possible alternative to EPS.
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.
– Good insulation materials have low thermal conductivity which is mainly related with the density of the material. Bio-composite insulation materials contribute to reduce the environmental footprint of buildings. The main goal of this study is to study the effectiveness of a self-growing, bio-composite building insulation material made of Miscanthus x giganteus and the mushroom Mycelium. Different mix proportions of Miscanthus and Mycelium were considered to identify the most suitable mixture to produce a porous composite which has a lower density. Scanning electron microscopy images were used to evaluate the microstructural geometry of the composite material. Thermal conductivity test was conducted on eight composite plates, and the results showed that the thermal conductivity of this new material is between 0.0882 and 0.104 Wm⁻¹K⁻¹. Moreover, other experiments were carried out to characterize the density, compressive strength and water absorption. In addition, fire resistant tests on composite plates with and without render were conducted, and it was found that the composite plates belong to the category EI15 according to the EN13501-2:2003. The initial results were found to be satisfactory to make a sustainable insulation material out of Miscanthus and Mycelium.
Wearable electronics featuring conformal attachment, sensitive perception and intellectual signal processing have made significant progress in recent years. However, when compared with living organisms, artificial sensory devices showed undeniable bulky shape, poor adaptability, and large energy consumption. To make up for the deficiencies, biological examples provide inspirations of novel designs and practical applications. In the field of biomimetics, nanomaterials from nanoparticles to layered two-dimensional materials are actively involved due to their outstanding physicochemical properties and nanoscale configurability. This review focuses on nanomaterials related to wearable electronics through bioinspired approaches on three different levels, interfacial packaging, sensory structure, and signal processing, which comprehensively guided recent progress of wearable devices in leveraging both nanomaterial superiorities and biorealistic functionalities. In addition, opinions on potential development trend are proposed aiming at implementing bioinspired electronics in multifunctional portable sensors, health monitoring, and intelligent prosthetics.
Recent works show that the plants can exhibit nonlinear memristive behavior when excited with low-frequency signals. However, in the literature, only linear bio-impedance models are extensively considered to model the electrical properties of biological tissues without acknowledging the nonlinear behavior. In this paper, we show with experiments, for the first time, the pinched hysteresis behavior in seven fruits and vegetables including tomato, orange, lemon, aubergine, and kiwi which exhibit single pinch-off point, and others such as carrot and cucumber exhibit double pinch-off points (i.e., three lobes). We also proposed a memristive fractional-order bio-impedance model by extending the Hayden bio-impedance model. The proposed model is used to fit the measurements of the seven fruits and vegetables showing very good matching.
Smart wearables sense and process information from the user's body and environment and report results of their analysis as electrical signals. Conventional electronic sensors and controllers are commonly, sometimes augmented by recent advances in soft electronics. Organic electronics and bioelectronics, especially with living substrates, offer a great opportunity to incorporate parallel sensing and information processing capabilities of natural systems into future and emerging wearables. Nowadays, fungi are emerging as a promising candidate to produce sustainable textiles to be used as eco-friendly bio wearables. To assess the sensing potential of fungal wearables, we undertook laboratory experiments on the electrical response of a hemp fabric colonised by oyster fungi Pleurotus ostreatus to mechanical stretching and stimulation with attractants and repellents. We have shown that it is possible to discern a nature of stimuli from the fungi electrical responses. The results paved a way towards the future design of intelligent sensing patches to be used in reactive fungal wearables.
Environmental pollution and scarcity of natural resources lead to an increased interest in developing more sustainable materials. For example, the traditional construction industry, which is largely based on the extraction of fossil fuels and raw materials, is called into question. A solution can be found in biologically augmented materials that are made by growing mycelium-forming fungal microorganisms on natural fibres rich in cellulose, hemicellulose and lignin. In this way, organic waste streams, such as agricultural waste, are valorised while creating a material that is biodegradable at the end of its life cycle – a process that fits in the spirit of circular economy. Mycelium-based materials have properties that are promising for a wide range of applications, including the use as construction materials. Despite this promise, the applicability and the practicality of these materials are largely unexplored and moreover, individual studies use a wide range of different experimental approaches and non-standardized procedures. In this review, we critically evaluate existing data on the composition of mycelium-based materials and process variables with the aim of providing a comprehensive framework of the production process. The framework illustrates the many input factors during the production that have an impact on the final characteristics of the material, and the unique potential to deploy more tuneable levels in the fabrications process that can serve to prototype a diversity of new unprecedented applications. Furthermore, we determine the applicability of existing data and identify knowledge gaps. This framework is valuable in identifying standardized approaches for future studies and in informing the design and process of new applications of mycelium-based materials.
Memristors represent the fourth electrical circuit element complementing resistors, capacitors and inductors. Hallmarks of memristive behavior include pinched and frequency-dependent I–V hysteresis loops and most importantly a functional dependence of the magnetic flux passing through an ideal memristor on its electrical charge. Microtubules (MTs), cylindrical protein polymers composed of tubulin dimers are key components of the cytoskeleton. They have been shown to increase solution’s ionic conductance and re-orient in the presence of electric fields. It has been hypothesized that MTs also possess intrinsic capacitive and inductive properties, leading to transistor-like behavior. Here, we show a theoretical basis and experimental support for the assertion that MTs under specific circumstances behave consistently with the definition of a memristor. Their biophysical properties lead to pinched hysteretic current–voltage dependence as well a classic dependence of magnetic flux on electric charge. Based on the information about the structure of MTs we provide an estimate of their memristance. We discuss its significance for biology, especially neuroscience, and potential for nanotechnology applications.
Much is already understood about the anatomical and physiological mechanisms behind the linear, electrical properties of biological tissues. Studying the non-linear electrical properties, however, opens up for the influence from other processes that are driven by the electric field or movement of charges. An electrical measurement that is affected by the applied electrical stimulus is non-linear and reveals the non-linear electrical properties of the underlying (biological) tissue; if it is done with an alternating current (AC) stimulus, the corresponding voltage current plot may exhibit a pinched hysteresis loop which is the fingerprint of a memristor. It has been shown that human skin and other biological tissues are memristors. Here we performed non-linear electrical measurements on human skin with applied direct current (DC) voltage pulses. By doing so, we found that human skin exhibits non-volatile memory and that analogue information can actually be stored inside the skin at least for three minutes. As demonstrated before, human skin actually contains two different memristor types, one that originates from the sweat ducts and one that is based on thermal changes of the surrounding tissue, the stratum corneum; and information storage is possible in both. Finally, assuming that different physiological conditions of the skin can explain the variations in current responses that we observed among the subjects, it follows that non-linear recordings with DC pulses may find use in sensor applications.
Mycelium composites are an emerging class of cheap and environmentally sustainable materials experiencing increasing research interest and commercialisation in Europe and the United States for construction applications. These materials utilise natural fungal growth as a low energy bio-fabrication method to upcycle abundant agricultural by-products and wastes into more sustainable alternatives to energy intensive synthetic construction materials. Mycelium composites have customisable material properties based on their composition and manufacturing process and can replace foams, timber and plastics for applications, such as insulation, door cores, panelling, flooring, cabinetry and other furnishings. Due to their low thermal conductivity, high acoustic absorption and fire safety properties outperforming traditional construction materials, such as synthetic foams and engineered woods, they show particular promise as thermal and acoustic insulation foams. However, limitations stemming from their typically foam-like mechanical properties, high water absorption and many gaps in material property documentation necessitate the use of mycelium composites as non- or semi-structural supplements to traditional construction materials for specific, suitable applications, including insulation, panelling and furnishings. Nonetheless, useful material properties in addition to the low costs, simplicity of manufacture and environmental sustainability of these materials suggest that they will play a significant role in the future of green construction.
Background:
The circular economy closes loops in industrial manufacturing processes and minimizes waste. A bio-based economy aims to replace fossil-based resources and processes by sustainable alternatives which exploits renewable biomass for the generation of products used in our daily live. A current trend in fungal biotechnology-the production of fungal-based biomaterials-will contribute to both.
Results:
This study gives an overview of various trends and development applications in which fungal mycelium is used as new and sustainable biomaterial. A patent survey covering the last decade (2009-2018) yielded 47 patents and patent applications claiming fungal biomass or fungal composite materials for new applications in the packaging, textile, leather and automotive industries. Furthermore, fungal-based materials are envisaged for thermal insulation and as fire protection materials. Most patents and patent applications describe the use of different lignin- and cellulose-containing waste biomass as substrate for fungal cultivations, covering 27 different fungal species in total. Our search uncovered that most patent activities are on-going in the United States and in China.
Conclusion:
Current patent developments in the field suggest that fungal bio-based materials will considerable shape the future of material sciences and material applications. Fungal materials can be considered as an excellent renewable and degradable material alternative with a high innovation potential and have the potential to replace current petroleum-based materials.
Microtubules (MTs) are cytoskeletal structures that play a central role in a variety of cell functions including cell division and cargo transfer. MTs are also nonlinear electrical transmission lines that produce and conduct electrical oscillations elicited by changes in either electric field and/or ionic gradients. The oscillatory behavior of MTs requires a voltage-sensitive gating mechanism to enable the electrodiffusional ionic movement through the MT wall. Here we explored the electrical response of non-oscillating rat brain MT sheets to square voltage steps. To ascertain the nature of the possible gating mechanism, the electrical response of non-oscillating rat brain MT sheets (2D arrays of MTs) to square pulses was analyzed under voltage-clamping conditions. A complex voltage-dependent nonlinear charge movement was observed, which represented the summation of two events. The first contribution was a small, saturating, voltage-dependent capacitance with a maximum charge displacement in the range of 4 fC/μm2. A second, major contribution was a non-saturating voltage-dependent charge transfer, consistent with the properties of a multistep memristive device. The memristive capabilities of MTs could drive oscillatory behavior, and enable voltage-driven neuromorphic circuits and architectures within neurons.
Reducing the use of non-renewable resources is a key strategy of a circular economy. Mycelium-based foams and sandwich composites are an emerging category of biocomposites relying on the valorization of lignocellulosic wastes and the natural growth of the living fungal organism. While growing, the fungus cements the substrate, which is partially replaced by the tenacious biomass of the fungus itself. The final product can be shaped to produce insulating panels, packaging materials, bricks or new-design objects. Only a few pioneer companies in the world retain a significant know-how, as well as the ability to provide the material characterization. Moreover, several technical details are not revealed due to industrial secrecy. According to the available literature, mycelium-based biocomposites show low density and good insulation properties, both related to acoustic and thermal aspects. Mechanical properties are apparently inferior in comparison to expanded polystyrene (EPS), which is the major synthetic competitor. Nevertheless, mycelium-based composites can display an enormous variability on the basis of: fungal species and strain; substrate composition and structure; and incubation conditions. The aim of the present review is to summarize technical aspects and properties of mycelium-based biocomposites focusing on both actual applications and future perspectives.
Abstract An electrical measurement is non-linear when the applied stimulus itself affects the electrical properties of the underlying tissue. Corresponding voltage-current plots may exhibit pinched hysteresis loops which is the fingerprint of a memristor (memory resistor). Even though non-linear electrical properties have been demonstrated for different biological tissues like apples, plants and human skin, non-linear measurements as such have not been defined, yet. We are studying the non-linear properties of human skin systematically and initiate non-linear measurements on biological tissues as a field of research in general by introducing applicable recording techniques and parameterization. We found under which voltage stimulus conditions a measurement on human skin is non-linear and show that very low voltage amplitudes are already sufficient. The non-linear properties of human skin originate from the sweat ducts, as well as, from the surrounding tissue, the stratum corneum and we were able to classify the overall skin memristor as a generic memristor. Pinched hysteresis loops vary largely among subjects; an indication for the potential use in biomedical sensor applications.
We propose that fungi Basidiomycetes can be used as computing devices: information is represented by spikes of electrical activity, a computation is implemented in a mycelium network and an interface is realized via fruit bodies. In a series of scoping experiments, we demonstrate that electrical activity recorded on fruits might act as a reliable indicator of the fungi's response to thermal and chemical stimulation. A stimulation of a fruit is reflected in changes of electrical activity of other fruits of a cluster, i.e. there is distant information transfer between fungal fruit bodies. In an automaton model of a fungal computer, we show how to implement computation with fungi and demonstrate that a structure of logical functions computed is determined by mycelium geometry.
We recorded extra-cellular electrical potential of fruit bodies of oyster fungi Pleurotus djamor. We demonstrated that the fungi generate action potential like impulses of electrical potential. Trains of the spikes are observed. Two types of spiking activity are uncovered: high-frequency (period 2.6 min) and low-frequency (period 14 min); transitions between modes of spiking are illustrated. An electrical response of fruit bodies to short (5 sec) and long (60 sec) thermal stimulation with open flame is analysed in details. We show that non-stimulated fruit bodies of a cluster react to the thermal stimulation, with a single action-potential like spike, faster than the stimulated fruit body does.
In order to improve energy performance of buildings, insulation materials (such as mineral glass and rock wools, or fossil fuel-based plastic foams) are being used in increasing quantities, which may lead to potential problem with materials depletions and landfill disposal. One sustainable solution suggested is the use of bio-based, biodegradable materials. A number of attempts have been made to develop biomaterials, such as sheep wood, hemcrete or recycled papers. In this paper, a novel type of bio insulation materials – mycelium is examined. The aim is to produce mycelium materials that could be used as insulations. The bio-based material was required to have properties that matched existing alternatives, such as expanded polystyrene, in terms of physical and mechanical characteristics but with an enhanced level of biodegradability. The testing data showed mycelium bricks exhibited good thermal performance. Future work is planned to improve growing process and thermal performance of the mycelium bricks.
This paper presents an innovative fungal mycelium-based biofoam. Three different mixing protocols with various substrate materials, including wood pulp, millet grain, wheat bran, a natural fiber, and calcium sulfate, and two packing conditions were tested to produce samples for physical, thermal, and mechanical property characterization. Dry density, thermal conductivity, elastic moduli, Poisson's ratio, and compressive strength were obtained. It was found that densely packed samples following Mixing Protocol II have the highest dry density, elastic moduli, compressive strength, and comparable thermal conductivity, and have met or exceeded like characteristics of the conventional polymeric thermal foams except dry density. The results demonstrate that this biofoam offers great potential for application as an alternative insulation material for building and infrastructure construction, particularly in cold regions, or as light-weight backfill material for geoengineering applications.
This research examines the use of a novel new renewable resource in acoustic absorption applications. The new material being tested is based on a fungi that is grown on semi-hydrophobic agricultural by-product substrates such as switch-grass, rice straw, sorghum stalks, flax shive, kenaf and hemp. The various substrates were tested as this novel composite is limited in the control over density, with the main control being the selection of the constituent parts. The testing of the material for use in acoustics utilized an impedance tube and measured the standing wave ratios in accordance to ISO standard 10534-1. The results of the study show the mycelium based boards are a promising bio-based composite alternative to standard traditional foam insulation board. Results suggest an optimal performance at the key automotive road noise frequency of 1000 Hz. A further advantage provided by this new material is that it can be produced economically in comparison to the traditional petroleum based foams with the further advantage of bio-degradation when the product is disposed of at its end-of-life use. Based upon this work, future research is planned to examine this novel new composite in other acoustic applications where shape modifications can further enhance the performance.
A striking difference between brain-inspired neuromorphic processors and
current von Neumann processors architectures is the way in which memory and
processing is organized. As Information and Communication Technologies continue
to address the need for increased computational power through the increase of
cores within a digital processor, neuromorphic engineers and scientists can
complement this need by building processor architectures where memory is
distributed with the processing. In this paper we present a survey of
brain-inspired processor architectures that support models of cortical networks
and deep neural networks. These architectures range from serial clocked
implementations of multi-neuron systems to massively parallel asynchronous ones
and from purely digital systems to mixed analog/digital systems which implement
more biological-like models of neurons and synapses together with a suite of
adaptation and learning mechanisms analogous to the ones found in biological
nervous systems. We describe the advantages of the different approaches being
pursued and present the challenges that need to be addressed for building
artificial neural processing systems that can display the richness of behaviors
seen in biological systems.
Memristor, the missing fourth passive circuit element predicted forty years ago by Chua was recognized as a nanoscale device in 2008 by researchers of a H. P. Laboratory. Recently the notion of memristive systems was extended to capacitive and inductive elements, namely, memcapacitor and meminductor whose properties depend on the state and history of the system. In this paper, we use fractional calculus to generalize and provide a mathematical paradigm for describing the behavior of such elements with memory. In this framework, we extend Ohm's law to the generalized Ohm's law and prove it.
Memristors are novel devices, useful as memory at all hierarchies. These devices can also behave as logic circuits. In this paper, the IMPLY logic gate, a memristor-based logic circuit, is described. In this memristive logic family, each memristor is used as an input, output, computational logic element, and latch in different stages of the computing process. The logical state is determined by the resistance of the memristor. This logic family can be integrated within a memristor-based crossbar, commonly used for memory. In this paper, a methodology for designing this logic family is proposed. The design methodology is based on a general design flow, suitable for all deterministic memristive logic families, and includes some additional design constraints to support the IMPLY logic family. An IMPLY 8-bit full adder based on this design methodology is presented as a case study.
On April 30th 2008, the journal Nature announced that the missing circuit
element, postulated thirty-seven years before by Professor Leon O. Chua has
been found. Thus, after the capacitor, the resistor and the inductor, the
existence of a fourth fundamental element of electronic circuits called
"memristor" was established. In order to point out the importance of such a
discovery, the aim of this article is first to propose an overview of the
manner with which the three others have been invented during the past
centuries. Then, a comparison between the main properties of the singing arc,
i.e. a forerunner device of the triode used in Wireless Telegraphy, and that of
the memristor will enable to state that the singing arc could be considered as
the oldest memristor.
Since polystyrene is non-biodegradable, a biodegradable material that is eco-friendly is being sought
as a substitute for packaging and insulation board consumers. One such process, developed by
Ecovative Design, LLC, involves growing fungal species on agricultural biomass to produce an ecofriendly
packaging product (EcoCradle™) and insulation panels (Greensulate™). The objective of
this research was to develop and evaluate six blends of processed cotton plant biomass (CPB)
materials as a substrate for colonization of selected fungi in the manufacture of molded packaging
material. The blends were comprised of processed CPB, cotton seed hulls, starch, and gypsum. The
four ingredients were the same mix percentage for all six blends with the particle size of the CPM
being the only difference. CPB particles sizes ranged from 0.1 to 51 mm. Tests were conducted to
evaluate the physical and mechanical properties of the six CPB blends. Test results revealed blends
that met or exceeded like characteristics of extruded polystyrene foam.
We investigated electrical circuitry of the Venus flytrap, Mimosa pudica and Aloe vera. The goal was to discover if these plants might have a new electrical component - a resistor with memory. This element was postulated recently and the researchers were looking for its presence in different systems. The analysis was based on cyclic current-voltage characteristic where the resistor with memory should manifest itself. We found that the electrostimulation of plants by bipolar sinusoidal or triangle periodic waves induces electrical responses in the Venus flytrap, Mimosa pudica and Aloe vera with fingerprints of memristors. Tetraethylammonium chloride, an inhibitor of voltage gated K(+) channels, transforms a memristor to a resistor in plant tissue. Our results demonstrate that a voltage gated K(+) channel in the excitable tissue of plants has properties of a memristor. This study can be a starting point for understanding mechanisms of memory, learning, circadian rhythms, and biological clocks.
Conventional neuro-computing architectures and artificial neural networks have often been developed with no or loose connections to neuroscience. As a consequence, they have largely ignored key features of biological neural processing systems, such as their extremely low-power consumption features or their ability to carry out robust and efficient computation using massively parallel arrays of limited precision, highly variable, and unreliable components. Recent developments in nano-technologies are making available extremely compact and low power, but also variable and unreliable solid-state devices that can potentially extend the offerings of availing CMOS technologies. In particular, memristors are regarded as a promising solution for modeling key features of biological synapses due to their nanoscale dimensions, their capacity to store multiple bits of information per element and the low energy required to write distinct states. In this paper, we first review the neuro- and neuromorphic computing approaches that can best exploit the properties of memristor and scale devices, and then propose a novel hybrid memristor-CMOS neuromorphic circuit which represents a radical departure from conventional neuro-computing approaches, as it uses memristors to directly emulate the biophysics and temporal dynamics of real synapses. We point out the differences between the use of memristors in conventional neuro-computing architectures and the hybrid memristor-CMOS circuit proposed, and argue how this circuit represents an ideal building block for implementing brain-inspired probabilistic computing paradigms that are robust to variability and fault tolerant by design.
In laboratory experiments, we demonstrate that protoplasmic tubes of the acellular slime mould Physarum polycephalum show current versus voltage profiles consistent with memristive systems, and that this effect is due to the living protoplasm of the mould. This complements previous findings on memristive properties of other living systems (human skin and blood) and contributes to the development of self-growing bio-electronic circuits. Distinctive asymmetric V-I curves which were occasionally observed when the internal current is on the same order as the driven current, are well-modelled by the concept of active memristors.
The memristor is basically a resistor with memory, so that the resistance is dependent on the net amount of charge having passed through the device. It is the regarded the fourth fundamental component, in addition to the resistor, capacitor and inductor, that can be deduced from the four basic circuit variables; current, voltage, charge and magnetic flux. We show that memristors can be used for modelling electrical properties of human skin. In particular is electro-osmosis in human sweat ducts of memristive nature.
The search for new nonvolatile universal memories is propelled by the need for pushing power-efficient nanocomputing to the next higher level. As a potential contender for the next-generation memory technology of choice, the recently found "the missing fourth circuit element", memristor, has drawn a great deal of research interests. In this paper, we characterize the fundamental electrical properties of memristor devices by encapsulating them into a set of compact closed-form expressions. Our derivations provide valuable design insights and allow a deeper understanding of key design implications of memristor-based memories. In particular, we investigate the design of read and write circuits and analyze data integrity and noise-tolerance issues.
In the circular economy, reduction of the vigorous usages of nonrenewable resources is becoming the leading scenario. Fungal mycelium is the vegetative part of fungus consisting of a number of filamentous fibers that extend out of the fungus and is considered to be natural, fast growing, safe, and renewable. The ability to form self-assembling bonds helps them to grow quickly on biological and agricultural wastes and produce miles of thin fibers which bind to the substrate to form a strong biodegradable material and can easily be shaped for the production of packaging materials, architecture, and various new designed objects. With the benefit of cost-effective raw materials and sustainable substitute to polystyrene like hazardous synthetic materials, this mycelia-based material is becoming the material of choice. This chapter reviews the present scenario of technology-based mushroom cultivation using wastes generated from the agricultural industries and also focuses on a variety of utilizations as an alternative replacement for synthetic polystyrene.
Using the earth-abundant natural biomaterials to manufacture functional electronic devices meets the sustainable requirement of green electronics, especially for the practical application of memristors in data storage and neuromorphic computing. However, the sneak currents flowing though the unselected cells in a large-scale cross-bar memristor array is one of the major problems which need to be tackled. The self-selecting memristors can solve the problem to develop compact and concise integrated circuits. Here, a sustainable natural biomaterial (anthocyanin, C15H11O6) extracted from plant tissue is demonstrated for ions and electron transport. The capacitive-coupled memristive behavior of as-prepared bioelectronic device can be significantly modulated by diethylmethyl(2-methoxyethyl)ammoium bis(trifluoromethylsulfonyl)imide (DEME-TFSI) ionic liquid (IL). Furthermore, graphene was inserted into biomaterial matrix to manipulate the memristive effects by graphene protonation. This results in a battery-like self-selective memristive effect. This phenomenon is explained by a physical model and density functional theory (DFT) based first-principles calculations. Finally, the self-selective behavior was applied in 0T-1R array configuration, which indicates the battery-like self-selecting biomemristor has potential applications in the brain-inspired computing, data storage systems, and high-density device integration.
Plants have sensory, short, and long-term memory. Possible candidates for memory in plants are memristors; resistors with memory. Memristors have been found in seeds, plants, flowers, and fruits. The electrostimulation of plants by bipolar periodic waves can induce electrical responses with fingerprints of volatile or non-volatile memristors. Here we show that the electrostimulation of the Venus flytrap by unipolar sinusoidal or triangular periodic electrical trains induces electrical responses in plants with fingerprints of volatile memristors. The discovery of volatile generic memristors in plants opens up new directions in the modeling and understanding of electrical phenomena in the plant kingdom.
A fungal colony maintains its integrity via flow of cytoplasm along mycelium network. This flow, together with possible coordination of mycelium tips propagation, is controlled by calcium waves and associated waves of electrical potential changes. We propose that these excitation waves can be employed to implement a computation in the mycelium networks. We use FitzHugh-Nagumo model to imitate propagation of excitation in a single colony of Aspergillus niger. Boolean values are encoded by spikes of extracellular potential. We represent binary inputs by electrical impulses on a pair of selected electrodes and we record responses of the colony from sixteen electrodes. We derive sets of two-inputs-on-output logical gates implementable the fungal colony and analyse distributions of the gates.
Hypothesis:
Tubulin is a key protein of the cytoskeleton, forming networks of microtubules (MTs). These networks are vital for many aspects of a cell, including intra-cellular transport. It has been suggested by others that this network could be responsible for sub-cellular information processing, which naturally raises the question of whether such a system could be exploited for more artificial constructs. In this endeavour, this paper studies the electrical properties of Taxol-stabilised MT ensembles.
Experiments:
Electrical experiments were conducted on samples containing MTs. Measurements were made using iridium-coated needle electrodes on a droplet. Cyclic voltammetry was performed, by sweeping through a DC voltage range of [-1.2,+1.2] V. AC measurements were also taken, between 1 kHZ and 10 MHz, and with a DC bias. Separately, pulse train stimulation were conducted, with an amplitude of 0.5 V and duration of 1 ms.
Findings:
Cyclic voltammetry experiments reveal that the MT droplets act as electrical switches, under the experimental conditions. This is partly revealed in a substantial hysteresis. The stimulation of a MT droplet with a positive fast-impulse resulted in oscillation of the droplet's resistance, not observed in control experiments. Taxol-stabilised MT samples proved to be mem-resistive/mem-inductive, therefore the history of their electrical characterisation is able to change their response and behaviour. If the history of electrical stimuli is the same, so is the response. These findings pave a way towards future designs of MT-based sensing and computing devices, including data storage featuring liquid states.
This paper proposes the realization of grounded and floating fractional order mem-elements (FOMEs) based on two- and three-port mutators, respectively. Three different topologies based on two-port mutators are implemented using the four members of the second-generation current conveyor (CCII) family which is useful to achieve several realizations for the same circuit. The Fractional Order Mem-capacitor (FOMC) and Fractional Order Mem-inductor (FOMI) are realized using different combinations of memristor and fractional order capacitor (FOC) plus resistors. In addition, the generalization of the three-port mutator increases the flexibility to design the floating FOMI and FOMC mutators. The order α of the employed FOC affects the location of the pinched point and the hysteresis loop area. The q − v of FOMC and φ − i of FOMI curves are presented showing the movement of the pinched point location and the hysteresis loop area with different α at different applied frequency. Circuit simulations and experimental results for the mutator circuits are introduced to validate the theoretical findings.
Leon Chua postulated the memristor, a resistor with memory, in 1971 and the first solid-state memristor was built in 2008. Recently, we found memristors in vivo as components of plasma membranes in plants, fruits, roots and seeds. A memristor is a nonlinear element; its current–voltage characteristic is similar to that of a Lissajous pattern. The analysis of presence of memristors in apple fruits is based on cyclic voltam-metric characteristics at different frequencies of bipolar voltage waves. The electrostimulation of apple fruits by bipolar periodic triangular or sinusoidal voltage waves induces electrical responses with fingerprints of memristors. Tetraethylammonium chloride, an inhibitor of K + ion channels, transforms memristors to resistors in apple fruits. Memristive properties of apple fruits are linked to the properties of voltage gated K + ion channels. The shape of cyclic voltammograms depends on frequency bipolar triangular or sinusoidal waves. The analytical model of a memristor with a capacitor connected in parallel exhibits different characteristic behavior at low and high frequency of applied voltage, which is the same as experimental data obtained by cyclic voltammetry in vivo. The discovery of memristors in fruits creates a new direction in the modeling and understanding of electrochemical phenomena in fruit ion channels and structures.
Our application of bionic engineering is novel: we are interested in developing hybrid hardware-wetware systems for music. This paper introduces receptacles for culturing Physarum polycephalum-based memristors that are highly accessible to the creative practitioner. The myxomycete Physarum polycephalum is an amorphous unicellular organism that has been found to exhibit memristive properties. Such a discovery has potential to allow us to move towards engineering electrical systems that encompass Physarum polycephalum components. To realise this potential, it is necessary to address some of the constraints associated with harnessing living biological entities in systems for real-time application. Within the paper, we present 3D printed receptacles designed to standardise both the production of components and memristive observations. Subsequent testing showed a significant decrease in growth time, increased lifespan, and superior similarity in component-to-component responses. The results indicate that our receptacle design may provide means of implementing hybrid electrical systems for music technology.
Flexible solution-processed memristors show different behaviour dependent on the choice of electrode material. Use of gold for both electrodes leads to switchable WORM (Write Once Read Many times) resistive devices. Use of aluminium for both electrodes allows both curved (wholly non-linear) and triangular (linear ohmic low resistance state) memristive switching resistance memories. A comparison device with an aluminium bottom electrode and gold top electrode only exhibited significant memristive resistance switching when the aluminium electrode was the anode, suggesting that the electrode is acting as a source/sink of oxygen anions. Using the gold electrode as the anode causes oxygen evolution and electrode deformation. We conclude aluminium is helpful for stabilising and promoting memristive behaviour in sol–gel TiO2 devices. On and Off resistance states were found to correlate to device size, and the relative proportions of curved to triangular switching devices could be affected by vacuum curing of the gel layer and compliance current. We postulate that: A. the curved memristor switching is a bulk action compliant with Chua's description of a memristor; B. the triangular switching involves a filament conduction for the ohmic low resistance state.
Memristor, memcapacitor, and meminductor are new fundamental circuit elements, whose properties depend on the history of devices. This paper presents the physical analysis of these memory devices. Three simple examples are given for the memristor, memcapacitor, and meminductor, and are then generalized to reveal their general physical origin. It is found that the memristance, memcapacitance, and meminductance are caused by different combinations of nonlinear electric responses. The mathematical expressions for the currents through any voltage-driven memristor, memcapacitor, and meminductor are given, and the corresponding expressions for the memristance, memcapacitance, and meminductance are derived. Moreover, a method to determine the charge–flux relationship of a memristor is proposed.
This paper presents an in-depth review of the memristor from a rigorous circuit-theoretic perspective, independent of the material the device is made of. From an experimental perspective, a memristor is best defined as any two-terminal device that exhibits a pinched hysteresis loop in the voltage–current plane when driven by any periodic voltage or current signal that elicits a periodic response of the same frequency. This definition greatly broadens the scope of memristive devices to encompass even non-semiconductor devices, both organic and inorganic, from many unrelated disciplines, including biology, botany, brain science, etc. For pedagogical reasons, the broad terrain of memristors is partitioned into three classes of increasing generality, dubbed Ideal Memristors, Generic Memristors, and Extended Memristors. Each class is distinguished from the others via unique fingerprints and signatures. This paper clarifies many confusing issues, such as non-volatility, dc V–I curves, high-frequency v–i curves, local activity, as well as nonlinear dynamical and bifurcation phenomena that are the hallmarks of memristive devices. Above all, this paper addresses several fundamental issues and questions that many memristor researchers do not comprehend but are afraid to ask.
An experimental study on a physical model of memristor made from human blood (as material of resistor) is presented. The model manifests memristor characteristics as defined by Professor Leon Chua (1971), Strukov (2008) and William (2008). Speculative potential applications in human healthcare science and electronic memory circuit science/technology is envisaged.
Recent research in nanotechnology has led to the practical realization of nanoscale devices that behave as memristors, a device that was postulated in the seventies by Chua based on circuit theoretical reasonings. On the other hand, neuromorphic engineering, a discipline that implements physical artifacts based on neuroscience knowledge, has related neural learning mechanisms to the operation of memristors. As a result, neuro-inspired learning architectures can be proposed that exploit nanoscale memristors for building very large scale systems with very dense synaptic-like memory elements. At present, the deep understanding of the internal mechanisms governing memristor operation is still an open issue, and the practical realization of very large scale and reliable ?memristive fabric? for neural learning applications is not a reality yet. However, in the meantime, researchers are proposing and analyzing potential circuit architectures that would combine a standard CMOS substrate with a memristive nanoscale fabric on top to realize hybrid memristor-CMOS neural learning systems. The focus of this paper is on one such architecture for implementing the very well established Spike-Timing-Dependent-Plasticity (STDP) learning mechanism found in biology. In this paper we quickly review spiking neural systems, STDP learning, and memristors, and propose a hybrid memristor-CMOS system architecture with the potential of implementing a large scale STDP learning spiking neural system. Such architecture would eventually allow to implement real-time brain-like processing learning systems with about neurons and synapses on one single Printed Circuit Board (PCB).
A three-electrode hybrid molecular electronic element based on polyaniline (PANI) emeraldine base–polyethylene oxide/LiCl was fabricated and tested. Source and drain electrodes were connected to the conducting polymer layer. Solid electrolyte was deposited as a narrow stripe over the PANI film, and the third electrode (gate), maintained at ground potential, was attached to it. Drain and gate currents were measured during a drain voltage sweep. Drain voltage–current characteristics revealed a rectifying behavior, while gate characteristics were similar to those for cyclic voltammograms. Such behavior was attributed to the electrochemical control of the redox state (and hence of conductivity) of PANI area under the solid electrolyte. The device was stable and reproducible with robust electrical characteristics. In particular, an asymmetry in time relaxation due to ion diffusion was found; a possible application of this to the use of this device in adaptive conducting networks is proposed.
The Hodgkin-Huxley model for action potential generation in biological axons is central for understanding the computational capability of the nervous system and emulating its functionality. Owing to the historical success of silicon complementary metal-oxide-semiconductors, spike-based computing is primarily confined to software simulations and specialized analogue metal-oxide-semiconductor field-effect transistor circuits. However, there is interest in constructing physical systems that emulate biological functionality more directly, with the goal of improving efficiency and scale. The neuristor was proposed as an electronic device with properties similar to the Hodgkin-Huxley axon, but previous implementations were not scalable. Here we demonstrate a neuristor built using two nanoscale Mott memristors, dynamical devices that exhibit transient memory and negative differential resistance arising from an insulating-to-conducting phase transition driven by Joule heating. This neuristor exhibits the important neural functions of all-or-nothing spiking with signal gain and diverse periodic spiking, using materials and structures that are amenable to extremely high-density integration with or without silicon transistors.
The realization of logic operations within passive crossbar memory arrays is a promising approach to expand the fields of application of such architectures. Material implication was recently suggested as the basic function of memristive crossbar junctions, and single bipolar resistive switches (BRS) as well as complementary resistive switches (CRS) were shown to be capable of realizing this logical functionality. Based on a systematic analysis of the Boolean functions, we demonstrate here that 14 of 16 Boolean functions can be realized with a single BRS or CRS cell in at most three sequential cycles. Since the read-out step is independent of the logic operation steps, the result of the logic operation is directly stored to memory, making logic-in-memory applications feasible.