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Enzyme‐enabled biobatteries are promising green options to power the next‐generation of bioelectronics and implantable medical devices. However, existing power sources based on enzymatic biofuel chemistry exhibit limited scale‐down feasibility due to the solid and bulky battery structures. Therefore, miniature and soft alternatives are needed for integration with implants and tissues. Here, a biobattery built from nanolitre droplets, fuelled by the enzyme‐enabled oxidation of reduced nicotinamide adenine dinucleotide, generates electrical outputs and powers ion fluxes in droplet networks. Optimization of the droplet biobattery components ensures a stable output current of ~13,000 pA for over 24 h, representing a more than 600‐fold increase in output over previous approaches, including light‐driven processes. The enzyme‐enabled droplet biobattery opens new avenues in bioelectronics and bioiontronics, exemplified by tasks such as the ability to drive chemical signal transmission in integrated synthetic tissues. [ABSTRACT FROM AUTHOR]

Human society annually produces nearly 100 billion gallons of wastewater, containing approximately 3600 GWh of energy. This study introduces a proof of concept utilizing graphene materials to extract and instantly store this energy. A hybrid device, mimicking a microbial fuel cell, acts as both a battery and supercapacitor. Wastewater serves as the electrolyte, with indigenous microorganisms on the graphene electrode acting as biocatalysts. The device features a capacitive electrode using a 3D nickel foam modified with a plasma-exfoliated graphene mixture. Compared to controls, the Gr/Ni configuration shows a 150-fold increase in power output (2.58 W/m2) and a 48-fold increase in current density (12 A/m2). The Gr/Ni/biofilm interface demonstrates outstanding charge storage capability (19,400 F/m2) as confirmed by electrochemical impedance spectroscopy. Microscopy, spectroscopy, and electrochemical tests were employed to elucidate the superior performance of Gr/Ni electrodes. Ultimately, the capacitive energy extracted from wastewater can power small electrical equipment in water infrastructure, addressing energy needs in remote regions without access to a typical power grid. [ABSTRACT FROM AUTHOR]

Human society annually produces nearly 100 billion gallons of wastewater, containing approximately 3600 GWh of energy. This study introduces a proof of concept utilizing graphene materials to extract and instantly store this energy. A hybrid device, mimicking a microbial fuel cell, acts as both a battery and supercapacitor. Wastewater serves as the electrolyte, with indigenous microorganisms on the graphene electrode acting as biocatalysts. The device features a capacitive electrode using a 3D nickel foam modified with a plasma-exfoliated graphene mixture. Compared to controls, the Gr/Ni configuration shows a 150-fold increase in power output (2.58 W/m2) and a 48-fold increase in current density (12 A/m2). The Gr/Ni/biofilm interface demonstrates outstanding charge storage capability (19,400 F/m2) as confirmed by electrochemical impedance spectroscopy. Microscopy, spectroscopy, and electrochemical tests were employed to elucidate the superior performance of Gr/Ni electrodes. Ultimately, the capacitive energy extracted from wastewater can power small electrical equipment in water infrastructure, addressing energy needs in remote regions without access to a typical power grid.

This work presents the development of an enzyme fuel cell, termed "BioBattery", that utilizes multicopper oxidases as the anodic enzyme in a non-diffusion limited system. We evaluated various enzyme variants as the anode, including multicopper oxidase from Pyrobaculum aerophilum , laccase from Trametes versicolor , and bilirubin oxidase from Myrothecium verrucaria. Several combinations of cathodes were also examined, focusing on the reduction of oxygen as the primary electron acceptor. The optimal pairing used multicopper oxidase from Pyrobaculum aerophilum as the anode and amine reactive phenazine ethosulfate modified bovine serum albumin as the cathode. BioBattery was integrated with our previously developed BioCapacitor, proving capable of consistently powering a 470 μF capacitor, positioning it as a modular power source for wearable and implantable systems. This research work addresses and overcomes some of the fundamental limitations seen in enzyme fuel cells, where power and current are often limited by substrate accessibility to the active electrode surface. (152 words). • A novel enzyme fuel cell, termed "BioBattery" was developed. • BioBattery utilizes multicopper oxidases as the anodic enzyme. • BioBattery delivers continuous, stable power independently of substrate diffusion from the bulk environment. • The optimal BioBattery configuration utilizes an extremophile derived multicopper oxidase. • Successfully integrated the BioBattery with a "BioCapacitor," consistently powering a 470 μF capacitor within 25 s. [ABSTRACT FROM AUTHOR]

The next generation of textile-based wearable batteries will be built on 1-D fiber/yarn through a bottom-up approach. Functional yarn fibers will be weaved or knitted into 2-D or 3-D batteries of a large textile, but the bottom-up strategy from 1-D yarn fibers is at a very early stage and requires a long-term focus. Here, we demonstrate an innovative 1-D yarn biobattery, a step toward a potential solution for scaling-up production of the wearable batteries. Our 1-D biobattery used microorganisms as a biocatalyst to harvest electrons from microbial metabolism. This yarn biobattery can be easily scaled up by weaving functional yarns into 2-D or 3-D batteries, connecting multiple batteries in series and parallel. [2020-0084] [ABSTRACT FROM AUTHOR]

This study describes a novel approach for real-time energy harvesting and performance diagnostics of a solid anolyte microbial fuel cell (SA-MFC) representing a prototype smart biobattery. The biobattery power output was maximized in real time by combining intermittent power generation with a Perturbation-and-Observation algorithm for maximum power point tracking. The proposed approach was validated by operating the biobattery under a broad range of environmental conditions affecting power production, such as temperature (4-25 °C), NaCl concentration (up to 2 g L-1), and carbon source concentration. Real-time biobattery performance diagnostics was achieved by estimating key internal parameters (resistance, capacitance, open circuit voltage) using an equivalent electrical circuit model. The real time optimization approach ensured maximum power production during 388 days of biobattery operation under varying environmental conditions, thus confirming the feasibility of biobattery application for powering small electronic devices in field applications. [ABSTRACT FROM AUTHOR]

In this work, biobatteries assembled using roll-to-roll screen printed enzymatic electrodes were characterised in terms of their electrical performance and storage stability. The enzymes and mediators used on the anode and cathode were glucose oxidase with ferrocenemethanol and laccase with ABTS, respectively. This study shows that besides rheological properties of enzyme inks used for the printing of the biobattery electrodes also adhesion of these electrodes to the printing substrate can be adjusted by varying the amount and composition of the binder in the ink. Another important observation is that the mediator has a strong impact on both the performance and the stability of the anode electrode. Consequently, electrochemical performance of biobatteries can be enhanced by adding fresh mediator into the battery during activation or by some other method preserving the activity of the mediator. Hence, this study discusses and sheds light on important practical aspects for up-scaling production process of biobatteries and also other printed bioelectronics.

Enzymatic biofuel cells can generate electricity directly from the chemical energy of biofuels in physiological fluids, but their power density is significantly limited by the performance of the cathode which is based on oxygen reduction for in vivo applications. An oxygen-independent and membrane-less glucose biobattery was prepared that consists of a dealloyed nanoporous gold (NPG) supported glucose dehydrogenase (GDH) bioanode, immobilised with the assistance of conductive polymer/Os redox polymer composites, and a solid-state NPG/MnO 2 cathode. In a solution containing 10 mM glucose, a maximum power density of 2.3 µW cm −2 at 0.21 V and an open circuit voltage (OCV) of 0.49 V were registered as a biobattery. The potential of the discharged MnO 2 could be recovered, enabling a proof-of-concept biobattery/supercapacitor hybrid device. The resulting device exhibited a stable performance for 50 cycles of self-recovery and galvanostatic discharge as a supercapacitor at 0.1 mA cm −2 over a period of 25 h. The device could be discharged at current densities up to 2 mA cm −2 supplying a maximum instantaneous power density of 676 μW cm −2 , which is 294 times higher than that from the biobattery alone. A mechanism for the recovery of the potential of the cathode, analogous to that of RuO 2 (Electrochim. Acta 42(23), 3541–3552) is described. [ABSTRACT FROM AUTHOR]

This study describes a novel approach for real-time energy harvesting and performance diagnostics of a solid anolyte microbial fuel cell (SA-MFC) representing a prototype smart biobattery. The biobattery power output was maximized in real time by combining intermittent power generation with a Perturbation-and-Observation algorithm for maximum power point tracking. The proposed approach was validated by operating the biobattery under a broad range of environmental conditions affecting power production, such as temperature (4–25 °C), NaCl concentration (up to 2 g L−1), and carbon source concentration. Real-time biobattery performance diagnostics was achieved by estimating key internal parameters (resistance, capacitance, open circuit voltage) using an equivalent electrical circuit model. The real time optimization approach ensured maximum power production during 388 days of biobattery operation under varying environmental conditions, thus confirming the feasibility of biobattery application for powering small electronic devices in field applications.

• Enzymatic bioelectrode characterized for energy generation and biosensing purposes. • Bilirubin oxidase immobilized on carbon paper using PBSE as bifunctional crosslinker. • Biobattery successfully applied in powering a digital watch for over 2 h. • Biosensor revealed high sensitivity (606 μA mM−1 cm−2) and low LOD (1.3 μM) for O 2. • Response maintained (88%) for 34 days through constant bioelectrode reutilization. Biological systems can be envisaged as energy-sustainable solutions for both microenergy production to power small electronics and sensing purposes. In the present work, an enzymatic bioelectrode was characterized as biocathode in the fabrication of a biobattery and as biosensor for dioxygen detection. Carbon fibre paper was selected as transducer given its unique tailoring and electrocatalytic characteristics, being modified with carbon nanotubes for subsequent attachment of bilirubin oxidase enzyme. The immobilization process was based on a simple but effective method using the crosslinker 1-pyrenebutanoic acid N-hydroxysuccinimide ester, which creates stable bonds by maintaining a good response (88%) for over 34 days. The biobattery, that consisted of a zinc anode coupled with the developed biocathode, produced an open circuit potential of 1.69 V and maximum power of 40 μW, being capable of powering a digital watch for over 2 h. When applied as a dioxygen biosensor, the biocathode revealed high sensitivity of 606 ± 22 μA mM−1 cm−2 and low limit of detection of 1.3 ± 0.2 μM in chronoamperometric measurements at +0.4 V. The application of bilirubin oxidase in the fabrication of biobatteries is scarcely studied even given its advantages over other dioxygen reduction enzymes. Likewise, the use of the remarkable features of CP in dioxygen biosensing is yet to be explored. Therefore, this work stands as an interesting opportunity in the development of relatively simple and affordable bioelectrodes viably intended for energy and biosensing applications. [Display omitted] [ABSTRACT FROM AUTHOR]

One of the problems with the use of enzymes as catalysts in biofuel cells is to achieve good contact between the enzyme and the electrode surface. One solution to this problem is the use of various nanostructures such as carbon nanotubes, fullerenes, graphene derivatives, gold nanoparticles, as well as mediators for the construction of electrodes. Acetosyringone and promazine adsorbed on glassy carbon electrodes (GCEs) covered with multiwall carbon nanotubes (MWCNTs) and laccase were used as biocathodes. These mediators showed very efficient adsorption on modified glassy carbon electrodes covered with MWCNTs and enabled efficient and stable adsorption of laccase, which acts as the bioelectrocatalyst. Very good electrical contact between the electrode surface and the laccase enzymatic active sites made it possible to increase the catalytic current density of oxygen-reduction by about 82% compared to electrodes without mediators. Application of acetosyringone and promazine used in the construction of biocathode also improved the current and power of the biobattery ca. twice comparing to the system without mediators. The device output reached the power that equaled approximately 2 mW/cm2 at 0.8 V and open circuit potential (OCP) was 1.6 V. The systems elaborated proved also useful in oxygen sensing and allowed to determine lower oxygen concentrations in solution compared to the GCE modified with MWCNTs and laccase alone. The electrode showed also better stability in long-timescale measurements.

A water-proof anti-drying enzymatic O 2 cathode for a deformable bioelectric skin patch was developed by laminating a thin membrane (50 μm thick) of polydimethylsiloxane (PDMS) to a bilirubin oxidase (BOD)-modified carbon fabric (CF) electrode. The PDMS membrane and the CF electrode were adhered so that a microspace serving as the oxygen reservoir was formed at their interface, enabling the operation of the patch even in a soaked condition for more than a few minutes. Even if the oxygen in the reservoir was depleted by soaking for too long, the patch performance could be recovered within a few tens of seconds by taking it out of the water, owing to the excellent oxygen-permeability of the thin PDMS membrane. The anti-drying effect of PDMS prolonged the lifetime of the bioelectric patch wrapped around a finger for more than 3 h while maintaining transdermal current of ∼20 μA cm−2. [Display omitted] • A water-proof enzymatic O 2 cathode for a bioelectric skin patch was developed. • A hydrophobic, oxygen-permeable membrane was laminated to the cathode electrode. • The microspace at their interface served as the oxygen reservoir. [ABSTRACT FROM AUTHOR]

Enzymatic biofuel cells are bioelectronic devices that utilize oxidoreductase enzymes to catalyze the conversion of chemical energy into electrical energy. This review details the advancements in the field of enzymatic biofuel cells over the last 30 years. These advancements include strategies for improving operational stability and electrochemical performance, as well as device fabrication for a variety of applications, including implantable biofuel cells and self-powered sensors. It also discusses the current scientific and engineering challenges in the field that will need to be addressed in the future for commercial viability of the technology. [ABSTRACT FROM AUTHOR]

The immobilization of redox enzymes on the surface of electrodes is a typical practice for enzymatic fuel cells ( EFCs) but enzyme immobilization usually results in low retaining enzymatic activities and low power densities. Here, we investigated an alternative solution - the use of nonimmobilized thermostable enzymes (e.g., NAD-based glucose 6-phosphate dehydrogenase and flavin-containing diaphorase) and a nonimmobilized mediator (i.e., benzyl viologen or 9,10-anthraquinone-2,7-disulphonic acid, AQDS) for achieving high power densities from glucose 6-phosphate in closed EFCs (called biobatteries). At the same enzyme loading, power densities of biobatteries increased in an order from the case of immobilized enzymes and immobilized vitamin K3 to the case of nonimmobilized enzymes and immobilized vitamin K3 to the case of nonimmobilized enzymes and nonimmobilized AQDS. The maximum power density of the biobattery based on nonimmobilized enzymes and AQDS was 1.1 mW cm−2 of anode at room temperature, 34-times of the biobattery based on immobilized enzymes and immobilized vitamin K3. When enzyme loading was increased by another 10-fold, the highest power density of biobattery was increased to 2.4 mW cm−2 at 37°C. The biobattery based on nonimmobilized enzymes and AQDS retained 60% of its initial current density after running for 2 h. When repeatedly being used for 6 rounds, the biobattery had 35% of its initial current density after 12 days. Our results suggest that closed biobatteries equipped with nonimmobilized thermostable enzymes and mediators feature simple system configuration and have high power densities. [ABSTRACT FROM AUTHOR]

A fully-integrated self-powered system on paper will work independently and self-sustainably as a low-cost and disposable diagnostic device in challenging field conditions such as resource-limited and remote regions. The paper-based power source is essential to create the paper-based system. In this work, a stackable and integrative 3-D paper-based bacteria-powered battery was developed. The battery was capable of generating power from microbial metabolism, delivering on-board energy to the next generation of paper-based systems with one drop of bacteria-containing liquid derived from renewable and sustainable water and wastewater sources (e.g. wastewater, municipal wastes, biomass and watershed) that are readily accessible in the local environment. An inexpensive air-breathing cathode was also created on paper with activated carbon on the sprayed Nickel electrode. By applying origami techniques, compact and stackable 3-D battery structures were created from 2-D sheets through high degrees of folding along pre-defined creases. The bacterial culture was added into two common inlets of the folded battery stack, through which it was transported into each battery. For operation, the battery stack was unfolded to expose all air-cathodes to the air, thereby maximizing their cathodic reactions. [ABSTRACT FROM AUTHOR]

Herein, a fully paper-based biobattery composed of four microbial fuel cell (MFC) units is evaluated, one that can be prepared in advance, stored, and quickly activated with virtually any available fluid. The biobattery uniquely utilizes Bacillus subtilis endospores as the storable anodic biocatalyst; the dormant, robust nature of B. subtilis endospores should allow for device preinoculation with spores followed by prolonged storage of the fully fabricated paper battery until needed. A germinant paper layer strategically fabricated above the spore-loaded anode layer contains all of the necessary chemical germinants and nutrient components required for the endospores to begin germination, exit dormancy, and return to fully metabolic vegetative bacterial cells that can generate electrical energy. This mechanism allows for the battery to be simply initiated via a wide range of available liquids. Bioelectricity generation of the battery is successfully demonstrated after introduction of a variety of artificial bodily fluids, including saliva, sweat, and urine, along with tap water. Since the biobattery has the capability of serially linking all 4 of its MFCs through simple dynamic folding, the device's total power output can be greatly enhanced; a single biobattery is able to achieve 0.56 V and 2.4 μW, which is beyond the ratings required for their intended application in single-use, disposable sensors. Therefore, this concept of integrating 4 spore-based MFCs into a single biobattery device with a built-in germinant layer offers a potential solution for stable, long-term storable power sources, displaying feasibility for integration with low power, disposable sensor applications. [Display omitted] • A fully paper-based, bodily fluid activated biobattery is created. • The biobattery utilizes Bacillus subtilis endospores as the anodic catalyst. • The dormant, robust nature of the endospores allows for storage of the battery. • The battery displays feasibility for integration with sensor applications. [ABSTRACT FROM AUTHOR]

Effective integration of electrochemical devices consisting of enzyme-based biobatteries together with high power double-layer type capacitors is discussed here. An ultimate goal is to overcome a typical drawback of enzymatic power sources (biofuel cells and biobatteries): although their energy is potentially high enough to fulfill the needs of small electronic devices, their power is often too low. It is demonstrated that properly selected capacitor can support operation of such a low power device simply by supplying appropriate power pulses with fast dynamic response that is required for many applications involving fluctuating loads. Our model integrated system is obtained by coupling a series of double-layer capacitors with well-behaved zinc/oxygen biobattery. The biobattery utilizes a stable cathodic material composed of covalently phenylated single-walled carbon nanotubes and the oxygen reduction enzyme, laccase, together with the hopeite-covered zinc rod acting as the anode. The enzymatic power source was characterized by the maximum power density of 1.8 mW cm, the open circuit voltage of 1.6 V. Nevertheless, under the 50 Ω loading, the voltage of biobattery (electrode surface areas of ca. 0.3 cm) drops to 0 V after 2 s. The practical performance (power stability) of a biobattery has significantly improved by its parallel connection to electrochemical capacitor. The importance of such capacitor's parameters as low resistance (not more than a few hundred of milliohms), proper capacitance, and leakage current (not higher than a few microamperes) is emphasized here. The potential utility of the optimized biobattery/supercapacitor system is discussed in terms of use as a source of power to operate a digital watch. [ABSTRACT FROM AUTHOR]

Abstract: Single walled carbon nanotubes (SWCNTs) were equipped with aryl residues by chemical reactions. These insoluble materials were used to substitute classical soluble mediators, which help to transfer electrical charge between the conducting electrode and the redox active center of enzyme molecules. The effect of different aryl residues on the efficiency of the catalytic reduction of dioxygen in the presence of laccase was systematically studied using voltammetry and measuring the power output of a biofuel cell. [Copyright &y& Elsevier]

Abstract: This research focused on the transition of biofuel cell technology to rechargeable biobatteries. The bioanode compartment of the biobattery consisted of NAD-dependent alcohol dehydrogenase (ADH) immobilized into a carbon composite paste with butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid serving as the electrolyte. Ferrocene was added to shuttle electrons to/from the electrode surface/current collector. The bioanode catalyzed the oxidation of ethanol to acetaldehyde in discharge mode. This bioanode was coupled to a cathode that consisted of Prussian Blue in a carbon composite paste with Nafion 212 acting as the separator between the two compartments. The biobattery can be fabricated in a charged mode with ethanol and have an open circuit potential of 0.8V in the original state prior to charging or in the discharged mode with acetaldehyde and have an open circuit potential of 0.05V. After charging it has an open circuit potential of 1.2V and a maximum power density of 13.0μWcm−3 and a maximum current density of 35.0μAcm−3, respectively. The stability and efficiency of the biobattery were studied by cycling continuously at a discharging current of 0.4mA and the results obtained showed reasonable stability over 50 cycles. This is a new type of secondary battery inspired by the metabolic processes of the living cell, which is an effective energy conversion system. [Copyright &y& Elsevier]

Abstract: In this paper, we have established that poly(neutral red), PNR, functions as an electrocatalyst for the reduction and oxidation of NAD+/NADH in a rechargeable biobattery environment. The reversibility of this catalyst was possible only with the addition of Zn2+ for complexation to the redox polymer. The zinc ion complexation with the polymer facilitates electron and proton transfer to/from the substrate and the NAD+/NADH coenzyme without forming covalent bonds between the nicotinamide and the substrate surface. This research presents use of this reversible catalyst in a rechargeable biobattery. The rechargeable battery includes a Prussian blue cathode and a bioanode including NAD+-dependent alcohol dehydrogenase and zinc complexed PNR. This bioanode was coupled to the cathode with Nafion® 212 acting as the ion exchange membrane separator between the two compartments. The biobattery has an open circuit potential of 0.545(±0.009)V when first assembled and 0.053(±0.005)V when fully discharged. However, when fully charged, the biobattery has an open circuit potential of 1.263(±0.051)V, a maximum power density of 16.3(±4.03) μWcm−3 and a maximum current density of 221(±13.2)μAcm−3. The efficiency and stability of the biobattery were studied by cycling continuously at a discharging rate of 1C and the results obtained showed reasonable stability over 50 cycles. [Copyright &y& Elsevier]

A homemade biobattery was studied from electrical point of view. The open circuit voltage for a 0.2 mA short circuit current was of 0.6 V. The maximum power for an internal resistance of 1.1 kΩ and a concentration of 109 cells/cm3 of Staphylococcus aureus was of 17.57 μW. [ABSTRACT FROM AUTHOR]

A substantial international community of biologists have proposed the electric eel Electrophorus electricus (Teleostei: Gymnotiformes) as an important candidate for genome sequencing. In this study, the authors outline the unique advantages that a genome sequencing project of this species would offer society for developing new ways of producing and storing electricity. Over tens of millions of years, electric fish have evolved an exceptional capacity to generate a weak (millivolt) electric field in the water near their body from specialized muscle-derived electric organs, and simultaneously, to sense changes in this field that occur when it interacts with foreign objects. This electric sense is used both to navigate and orient in murky tropical waters and to communicate with other members of the same species. Some species, such as the electric eel, have also evolved a strong voltage organ as a means of stunning prey. This organism, and a handful of others scattered worldwide, convert chemical energy from food directly into workable electric energy and could provide important clues on how this process could be manipulated for human benefit. Electric fishes have been used as models for the study of basic biological and behavioural mechanisms for more than 40 years by a large and growing research community. These fishes represent a rich source of experimental material in the areas of excitable membranes, neurochemistry, cellular differentiation, spinal cord regeneration, animal behaviour and the evolution of novel sensory and motor organs. Studies on electric fishes also have tremendous potential as a model for the study of developmental or disease processes, such as muscular dystrophy and spinal cord regeneration. Access to the genome sequence of E. electricus will provide society with a whole new set of molecular tools for understanding the biophysical control of electromotive molecules, excitable membranes and the cellular production of weak and strong electric fields. Understanding the regulation of ion channel genes will be central for efforts to induce the differentiation of electrogenic cells in other tissues and organisms and to control the intrinsic electric behaviours of these cells. Dense genomic sequence information of E. electricus will also help elucidate the genetic basis for the origin and adaptive diversification of a novel vertebrate tissue. The value of existing resources within the community of electric fish research will be greatly enhanced across a broad range of physiological and environmental sciences by having a draft genome sequence of the electric eel. [ABSTRACT FROM AUTHOR]