Search

Miniaturized microfluidic electrochemical energy devices can produce power without the need for a separator reducing a considerable amount of fabrication complications. Enzymatic biofuel cells, with glucose as a fuel, are capable of producing energy from biological fluids in the presence of biocatalysts. The tedious fabrication procedures can be avoided by making electrodes and microchannel using laser ablation technique on polyimide substrates. In this work, a microfluidic enzymatic biofuel cell (MEBFC) has been presented with CO2 laser-ablated microchannel and bioelectrodes using a mediatorless approach. Multiwalled carbon nanotubes (MWCNT) have been used as a promoter to enhance the electron transfer rate. The fabricated MEBFC shows good power performance supplying 4.7 μW/cm2 with a maximum open-circuit voltage of 260 mV.

The detection of microRNA (miRNA) in human serum has great significance for cancer prevention. Herein, a novel self-powered biosensing platform is developed, which effectively integrates an enzymatic biofuel cell (EBFC)-based self-powered biosensor with a matching capacitor for miRNA detection. A catalytic hairpin assembly and hybrid chain reaction are used to improve the analytical performance of EBFC. Furthermore, the matching capacitor is selected as an auxiliary signal amplifying device, and graphdiyne is applied as substrate material for EBFC. The results confirm that the developed method obviously increases the output current of EBFC, and the sensitivity can reach 2.75 μA/pM, which is 786% of pure EBFC. MiRNA can be detected in an expanded linear range of 0.1-100000 fM with a detection limit of 0.034 fM (S/N = 3). It can offer a selective and sensitive platform for nucleotide sequence detection with great potential in clinical diagnostics.

Membraneless microfluidic enzymatic biofuel cells (μEBFCs) operated under the co-laminar flow of fuel and oxidant often face cross-mixing issues, especially at low flow rates. In this work, we propose a new approach to design the single-stream μEBFC based on the investigation of relative positions of the electrodes at the top and bottom of the microchannel. To achieve this, a μEBFC was fabricated with multiwalled carbon nanotube (MWCNT) electrodes via a stencil method. The bioanode and biocathode were modified with glucose dehydrogenase and laccase via direct covalent bonding, respectively. The best results were attained by placing the cathode at the top and anode at the bottom of the microchannel in a Y-shaped two streamflow μEBFC. When a single electrolyte stream was used to achieve more practicality and ease of use, the performance was reduced by 40%. However, with the new design of electrodes in single-stream μEBFC, i.e. cathode at the top and anode at the bottom facing each other in the microchannel, the performance was recovered by 20%. This corresponds to maximum current and power density of 216 ± 12 μA cm−2 and 69.2 ± 9.2 μW cm−2, respectively. The stacking ability of the device was realized by connecting the two cells in series and parallel. The maximum power density delivered by the two single-stream μEBFCs’ stack reached 160 μW cm−2 at 0.3 V. Thus, this study validates the viability of using single-stream μEBFCs in large stacks to power microelectronics more simply and practically.

In this study, an amine-coordinated cobalt phthalocyanine (CoPc)-based anodic catalyst was fabricated by a facile process, to enhance the performance of hydrogen peroxide fuel cells (HPFCs) and enzymatic biofuel cells (EBCs). For this purpose, polyethyleneimine (PEI) was added onto the reduced graphene oxide and CoPc composite (RGO/CoPc) to create abundant NH2 axial ligand groups, for anchoring the Co core within the CoPc. Owing to the PEI addition, the onset potential of the hydrogen peroxide oxidation reaction was shifted by 0.13 V in the negative direction (0.02 V) and the current density was improved by 1.92 times (1.297 mA cm−2), compared to those for RGO/CoPc (0.15 V and 0.676 mA cm−2, respectively), due to the formation of donor–acceptor dyads and the prevention of CoPc from leaching out. The biocatalyst using glucose oxidase (GOx) ([RGO/CoPc]/PEI/GOx) showed a better onset potential and catalytic activity (0.15 V and 318.7 μA cm−2) than comparable structures, as well as significantly improved operational durability and long-term stability. This is also attributed to PEI, which created a favorable microenvironment for the enzyme. The maximum power densities (MPDs) and open-circuit voltages (OCVs) obtained for HPFCs and EBCs using the suggested catalyst were 105.2 ± 1.3 μW cm−2 (0.317 ± 0.003 V) and 25.4 ± 0.9 μW cm−2 (0.283 ± 0.007 V), respectively. This shows that the amine axial ligand effectively improves the performance of the actual driving HPFCs and EBCs.

Enzymatic biofuel cells (EBFCs) are promising renewable and implantable power sources, but it exhibits low power output due to enzyme structure. The enzyme’s catalytic center is deeply buried insid...

International audience; An enzymatic biofuel cell cathode was elaborated by nano-structuration and functionalization of graphite using two consecutive plasma treatments before immobilization of laccase as a biocatalyst to perform oxygen reduction reaction (ORR) by direct electron transfer ((DET). Nano-structuration of graphite surfaces by synthesis of vertical graphen-like carbon nanowalls (CNWs) was performed by microwave excited plasma enhanced chemical vapor deposition (PECVD). Atmospheric pressure plasma jet (APPJ) system was then used to functionalize chemically the CNWs surface via a rapid and dry route. A partial fractional design evidenced two significant parameters of the APPJ treatment in terms of ORR current density: the treatment time and the inter-distance between the plasma jet and the surface of the carbon material. With the optimized APPJ treatment parameters, a four-fold enhancement of the ORR current density (-440 ± 70 µA/cm2) could be obtained on CNWs, compared to graphite electrodes. The best current density obtained was about −1 mA/cm2 with oxidized laccase covalently immobilized on the electrode without any agitation of the solution, confirming the main importance of enzyme orientation on the electrode surface for efficient DET transfer, the relevance of electrode nanostructuration and the advantage of covalent linking of the protein on the electrode surface.

The present work establishes a simple, customized, and economical laser-induced graphene (LIG) material produced using a CO2 laser. The one-step LIG bioelectrodes have been further validated for Enzymatic Biofuel Cell (EBFC) application by integrating them into a microfluidic device, fabricated by the conventional soft-lithography on Polydimethylsiloxane (PDMS). This electrode and device manufacturing technology delivers a simple and quick fabrication method, which eliminates the necessity of any further amendment and post-processing. LIG electrodes were created at optimized CO2 laser (5.1 W power and 0.625 cm s−1 speed) irradiation which has been further modified by Multi-walled carbon nanotubes (CNT), called C-LIG electrodes, which offers improved performance and enzyme stability. In this novel study, CNT functionalized LIG electrodes have been incorporated into a microfluidic device for biofuel cell applications. LIG and C-LIG bioelectrodes have been integrated into a microfluidic device under the laminar fluid flow regime and the electrochemical and polarization study of the platform have been carried out. This C-LIG bioelectrodes integrated microfluidic device, without any metal catalyst, generated 2.2 μW/cm2 power density with an optimized 200 μl/min flow rate which is 1.37 times higher than the LIG bioelectrodes. Such novel and simple EBFC platform is amenable to further improvement for generating even more power output by optimizing the LIG formation, alternate nano-functionalisation and mediator based electrochemical analysis.

Due to increasing human health disorders like diabetes, heart rate fluctuations, and different ocular complications, implantable medical devices (IMD) and wearable devices are continuously developed. These can be used not only in medical facilities but also at work stations and homes. The main focus is to develop comfortable and economical medical devices. For this, bio-compatible bio-fuel cells have been employed for power generation and to overcome the replacement issues. The category of bio-chemical and electrode reaction plays an important role to classify the fuel cells (FC). These may include an enzymatic biofuel cell (EBFC), precious metal FC or a microbial fuel cell (MFC). EBFC can be seen effectively applied to pacemakers and glucometers due to their high activity within mild conditions. However, the short life span is still a major challenge. In this review article, we have discussed the earlier researches in the field of implantable medical devices utilizing enzymes, precious metals, and microorganism as catalysts. Moreover, we have critically discussed various applications of FCs for in-vitro medical devices i.e. glucometer, alcohol testers, wound treatment device, and more. Safety is the foremost concern in these devices. Along with this, special attention has been given to recently developed optical contact lenses as an alternative to glucometers. The fuel cell implantations is at the early stages of testing and the results have been in the favor of commercializing these devices.

The prospective of this work is to synthesize a new nanocomposite that serves as an electrode material for the immobilization of biomolecules. In this work surface-functionalized single-walled carbon nanotubes (f–COOH–SWCNTs), and hydrothermally synthesized surface defected 2D nanoplates wrapped by polpyrrole matrix was developed. The developed nanocomposite was utilized as the anode material for the immobilization of enzymes. Nanocomposite f-SWCNTs@Ppy@NiMoSe2 was characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the electrochemical methods including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). The electrochemically controlled bioanode reached to the open circuit potential (OCV) of 0.35 V and delivered the maximum current density of 9.01 mA cm−2 in 50 mM glucose concentration prepared in phosphate buffer solution (PBS) (pH 7.0) as the testing solution at 100 mVs−1 scan rates.

The conversion of biomass and other cellulose-based materials to clean energy has high promise for a sustainable world. Herein we present a green methodology to convert cellulose directly into electrical power output by utilizing cellulase complex and an enzymatic biofuel cell. An integrated FAD-dependent glucose dehydrogenase (FAD-GDH) based anode and a bilirubin oxidase-based cathode were used for the cell construction. Cellulase complex was utilized for the cellulose to glucose degradation which was then oxidized by the FAD-GDH based anode to generate bioelectrocatalytic currents. The generated electrons were subsequently transferred to a bilirubin oxidase-based cathode for the oxygen reduction reaction. The designed biofuel cell allows direct biomass to electricity conversion, operating under neutral pH and standard conditions. The constructed biofuel cell was optimized under different cell conditions and a maximal operational lifetime of 32 hours was achieved. The optimized cell reached an electrical power of ∼300 μW cm−2 and 600 μW cm−2 under atmospheric and oxygen saturated conditions, respectively. Overall, the introduced one-pot biofuel cell allows the generation of bias-free electrical power while only cellulose and O2 are required for its operation.

A modifiable, spontaneously formed and biocompatible polymer gel, composed of phosphorylcholine and N-hydroxysuccinimide ester, is reported, which can be subjected to postmodification by amine-cont...

Self-powered glucose biosensor (SPGB) is of great interest due to the advantages including single configuration, good stability and particularly no need of external power sources. Herein, a mediator-free SPGB with high sensitivity and good selectivity is constructed based on a hybrid enzymatic biofuel cell (EBFC) composed of a glucose oxidase/cobalt phthalocyanine/1-pyrenebutyric acid/buckypaper (GOD/CoPc/PBA/BP) bioanode and a MnO2/PBA/BP capacitive cathode. The efficient electron transfer from GOD to electrodes is achieved successfully through the anode oxidation of hydrogen peroxide (H2O2), one nature product of glucose oxidation catalyzed by GOD, thus avoiding the potential drawbacks posed by the use of redox mediators. CoPc servers as an efficient catalyst to lower the anode potential required by the reaction of H2O2 to 0.17 V. The MnO2/PBA/BP capacitive cathode is utilized because it can not only provide a high discharge potential and adequate capacitance to match the bioanode well, but also exhibit no potential interference to the anodic reaction. The concentration of glucose can be detected simply by measuring the output of the SPGB and a wide linear detection range from 0.5 to 8 mM has been obtained with high sensitivities of 48.66 and 32.12 μA·cm−2·mM−1 with and without stirring, respectively. The recoveries of glucose in grape juice and human serum are in the range from 99.5% to 101.2% with the relative standard deviation (RSD) less than 8%, indicating the good promise of the SPGB in sensing glucose in real samples.

Development of bioelectrodes with multiple virtues, such as biocompatibility, flexibility, versatility and cost-effectiveness, remains a huge area of research for multiple applications. Here, we delve upon fabricating carbon electrodes using a desktop PCB printer in a cost-and-time efficient manner (less than 2 min). Such printed carbon paste electrodes have been incorporated to develop an enzyme-based glucose biofuel cell to power various low-power biomedical devices and for biosensing. The bioelectrodes were prepared by electrodepositing gold nanorods followed by the immobilization of suitable enzymes. These bioelectrodes were tested for their electrochemical behavior and was setup as a Direct Electron Transfer (DET)-based enzymatic biofuel to be amenable for various physiological fluids, like tears, human saliva, whole blood and blood serum, due to its biocompatibility and efficiency. It delivered maximum energy of 3.18 µW/cm2 and 8.8 µW/cm2 from tears and human serum, respectively. These fabricated electrodes have huge potential to be incorporated in miniaturized devices as a renewable energy source for implantable and self-powered bioelectronics.

The enzymatic biofuel cell (EBFC) has been considered as a promising implantable energy generator because it can extract energy from a living body without any harm to the host. However, an unprotected enzyme will be destabilized and even eventually be deactivated in human blood. Thus, the performance of implantable EBFC has received barely any improvement. It is therefore a breakthrough in realizing a superior efficient EBFC that can work stably in human blood which relies in protecting the enzyme to defend it from the attack of biological molecules in human blood. Herein, we innovatively created a single-walled carbon nanotube (SWCNT) and cascaded enzyme-glucose oxidase (GOx)/horseradish peroxidase (HRP) coembedded hydrophilic MAF-7 biocatalyst (SWCNT-MAF-7-GOx/HRP). The SWCNT-MAF-7-GOx/HRP is highly stable in electrocatalytic activity even when it is exposed to high temperature and some molecular inhibitors. In addition, we were pleasantly surprised to find that the electrocatalytic activity of GOx/HRP in hydrophilic SWCNT-MAF-7 far surpasses that of the GOx/HRP in hydrophobic SWCNT-ZIF-8. In human whole blood, the SWCNT-MAF-7-GOx/HRP catalytic EBFC exhibits an eightfold increase in power density (119 μW cm-2 vs 14 μW cm-2) and 13-fold increase in stability in comparison with the EBFC based on an unprotected enzyme. In this study, the application of metal-organic framework-based encapsulation techniques in the field of biofuel cells is successfully realized, breaking a new path for creating implantable bioelectrical-generating devices.

Flexible enzymatic biofuel cell (EBFC) has been considered as an alternative power source for wearable devices, in which, the design of the substrate electrode is of significance for its mechanical...

A new cathodic catalyst is developed for improving the performance of membraneless enzymatic biofuel cell (EBC) by enhancing overall oxygen reduction reaction (ORR). In this catalyst, both hemin and glucose oxidase (GOx) are considered as enzymatic catalysts to facilitate H2O2 reduction reaction (HRR) and partial oxygen reduction reaction (PORR), respectively. Hemin is attached to amine group functionalized carbon nanotube (Amine-CNT) to form amide bond, and GOx is conjugated with two poly(dimethyl-diallylammonium chloride) (PDDA) layers to form sandwich-like structure. As a result, [Amine-CNT/Hemin]/PDDA/GOx/PDDA catalyst is completed. This catalyst plays a role in reducing the amount of GOx leached out and preserving the mass transfer of fuels, and finally, increasing the catalytic activity for cathodic reactions. According to electrochemical estimation, its onset potential reaches 0.4 V vs. Ag/AgCl and current density significantly increases to 323 μA cm−2. When the performance of membraneless EBC adopting this catalyst is measured, maximum power density is 24.1 ± 0.61 μW cm−2 and its activity preserves 82.1% after four weeks. This excellent result is because PORR and HRR are promoted by the rigid connection of GOx and hemin, which is mainly induced by the sandwich effect of GOx by PDDA layers.

A biofuel cell is a device that converts chemical energy into electrical energy through electro-biochemical reactions. In this type of cell, biocatalysts, which can be both enzymes and microorganisms or cells, are used to generate electrical energy. Biocatalysts are used in biofuel cells in two ways: 1) Biocatalysts can produce the fuel substrates required for fuel cells by biocatalytic reactions or metabolic processes. 2) Biocatalysts can participate in the electron transport chain between the fuel substrate and the electrode surface. Accordingly, biofuel cells can be divided into two groups: basic microbial cells and basic enzymatic cells. This article reviews the enzymatic fuel cell. These topics are reviewed: 1. Function of enzymatic biofuel cells. 2. Investigation of methanol / oxygen enzymatic biofuel cell. 3. Investigation of surface replacement of apoglucose oxidase on a gold electrode layered with PQQFAD. 4. Examination of samples made of biodiesel based on enzymes layered by enzymes. 5. Investigation of bioelectrocatalytic cathodes made of cyt / cox. 6. Investigation of biofuel cell implants in animals.

Development of economical and mass-manufacturable bioelectrodes with desirable physical properties is one of the crucial challenges to realize automated and robust enzymatic biofuel cell (EBFC). This article focuses to develop customized CO2 laser-induced flexible graphene (LIFG) bioelectrodes on the polyamide substrate. The cost-efficiency and customization of LIFG bioelectrodes have been further demonstrated for EBFC application by integrating them into a microfluidic device, fabricated by the conventional soft lithography on polydimethylsiloxane (PDMS). First, the LIFG bioelectrodes were created at optimized CO2 laser (power and speed) irradiation, and characterization was performed to ensure the existence of graphene material. Subsequently, the surface morphological study of the noninduced polyamide sheet, LIFG, and LIFG with the relevant enzyme (GO x and laccase)-modified bioelectrodes has been characterized. Finally, various voltammetric electrochemical analyses of the modified LIFG bioelectrodes have been accomplished. After such an electrochemical study, the bioelectrodes were integrated into the microfluidic device and a power density of 13 $\mu \text{W}$ /cm2 ( $52~\mu \text{A}$ /cm2) was harnessed at an optimized fluid rate of $200~\mu \text{L}$ /min. By using this fabrication method, the proposed LIFG bioelectrodes have shown excellent potential for electrochemical redox and polarization performance in a microfluidic environment, with a huge scope to enrich the power output by introducing the additional cofactor-based electrochemistry and device stacking.

Aberrant DNA methylation catalyzed by DNA methyltransferases (MTase) has proved to be associated with human diseases such as cancers. Thus, the development of an efficient strategy to accurately detect DNA MTase is highly desirable in medical diagnostics. Herein, we proposed a robust "signal-on" enzymatic biofuel cell (EBFC)-based self-powered biosensing platform with excellent anti-interference ability for DNA MTase activity analysis and inhibitor screening. In the presence of target MTase, the MTase-catalyzed DNA methylation occurred and hindered the HpaII endonuclease-catalyzed dsDNA dissociation, which enabled more bilirubin oxidase (BOD) to immobilize at the cathode surface via amidation. Then, BOD-catalyzed oxygen reduction took place by accepting electrons generated at the anode via glucose oxidation, thus leading to an elevated open-circuit voltage value, the amplitude of which was directly related to MTase concentration. The direct detection limit of the M.SssI assay was down to 0.005 U/mL, which was lower than that of those reported results. Notably, the as-proposed protocol was competent to detect DNA MTase activity directly in human serum samples without enrichment and separation, and applicable to the screening of M.SssI inhibitors. Considering the virtues of the excellent anti-interference ability, no requirement of external power, simplicity, and high accuracy, the biosensing platform would hold great potential in DNA MTase bioassay and clinical diagnosis of cancers.

Enzymatic Biofuel Cell (EBC) represents a promising green source since it is capable of harvesting electricity from renewable and abundantly available biofuels using enzymes as catalysts. Nevertheless, nowadays long-term stability and low power output are currently the main concerns. To this end, several research studies focus on using complex tridimensional and highly expensive nanostructures as electrode support for enzymes. This increases cell performance whilst drastically reducing the economic feasibility needed for industrial viability. Thus, this paper analyzes a novel flow-based EBC consisting of covalent immobilized GOx (bioanode) and Laccase (biocathode) on a commercial flat conductive polymer. A suitable immobilization technique based on covalent ligands is carried out to enhance EBC durability. The experimental characterization demonstrates that the cell generates power over three weeks, reaching 590 mV and 2.41 µW cm−2 as maximum open circuit voltage and power density, respectively. The most significant contributions of this configuration are definitely ease of implementation, low cost, high scalability, and reproducibility. Therefore, such a design can be considered a step forward in the viable EBC industrialization process for a wide range of applications.

Owing to the high efficiency and specificity in moderate conditions, enzymatic biofuel cells (EBFCs) have gained significant interest as a promising energy source for wearable devices. However, the instability of the bioelectrode and the lack of efficient electrical communication between the enzymes and electrodes are the main obstacles. Herein, defect-enriched 3D graphene nanoribbons (GNRs) frameworks are fabricated by unzipping multiwall carbon nanotubes, followed by thermal annealing. It is found that defective carbon shows stronger adsorption energy towards the polar mediators than the pristine carbon, which is beneficial to improving the stability of the bioelectrodes. Consequently, the EBFCs equipped with the GNRs exhibit a significantly enhanced bioelectrocatalytic performance and operational stability, delivering an open-circuit voltage and power density of 0.62 V, 70.7 μW/cm2, and 0.58 V, 18.6 μW/cm2 in phosphate buffer solution and artificial tear, respectively, which represent the high levels among the reported literature. This work provides a design principle according to which defective carbon materials could be more suitable for the immobilization of biocatalytic components in the application of EBFCs.

Enzymatic biofuel cells (EBCs) represent a promising technology for biosensors, biodevices, and sustainable green energy applications, thanks to enzymes’ high specificity and catalytic efficiency. Nevertheless, drawbacks such as limited output power and short lifetime have to be solved. Nowadays, research is addressed to the use of 3D electrode structures, but the high cost and the industrialization difficulties of such electrodes represent a key issue. The purpose of the paper is thus to describe the use of a low-cost commercial conductive polymer (Sigracell® PV15) as support for the covalent immobilization of glucose oxidase and laccase, for bioanode and biocathode fabrication, respectively. Efficient immobilization protocols were determined for the immobilized enzymes in terms of employed linkers and enzyme concentrations, resulting in significant enzymatic activities for units of area. The analysis focuses specifically on the optimization of the challenging immobilization of laccase and assessing its stability over time. In particular, an optimum activity of 23 mU/cm2 was found by immobilizing 0.18 mg/cm2 of laccase, allowing better performances, as for voltage output and electrochemical stability, and a direct electron transfer mechanism to be revealed for the fabricated biocathode. This study thus poses the basis for the viable development of low-cost functional EBC devices for biomedical applications.

Enzymatic biofuel cells (EBFCs) are a subgroup of fuel cells that use enzymes as catalysts. EBFCs that utilize physiological substrates such as glucose or lactate are of great interest as implantable or wearable power sources to activate medical devices. This contribution introduces the working principles of EBFCs and summarizes recent progress in EBFC-enabled biosensors, pulse generators, and therapy. Biosensors with self-powered characteristic enjoy high selectivity, leading to potential “instrument-free” or “expensive-instrument-free” measurement. Autonomous pulse generation is based on the hybrid of EBFC and supercapacitor, which is promising for the application in medical related electrostimulation. By providing the direct electrical stimulation, or controllably releasing drug, EBFCs can also be used for self-powered therapeutic system. The further combination of self-powered sensing and treating enables EBFC as a possible platform of diagnostics and therapeutics. Future efforts can be focused on resolving the limited power density and lifetime of EBFC.

The authors have requested that this preprint be removed from Research Square.

Wearable devices continuously gain their popularity due to flexibility and opportunity to enable more applications and services, in particular, in healthcare industry. Guarantying long-term operation for these devices is among the key challenges at the design stage. In this work, we propose a multi-source energy harvesting system to address this problem. The proposed solution is based on two technologies namely an Enzymatic Biofuel Cell (BFC) and a low-temperature gradient Thermoelectric Generator (TEG) which are capable of generating power from human perspiration and heat, respectively. Upon designing BFC, we designed a functional circuit that combines it with the TEG. The resulting BFC has an output voltage of 200 mV and a power of about 7 nW. An array of BFCs is used as a source for initial push to start up the internal logical control circuit of the DC-DC controller. The low-temperature gradient TEG with an output voltage ranging from 40 mV to 70 mV and a constant measured output power of 160 uW is used together with the BFCs for energy harvesting upon the initial starting of the DC-DC controller.

To meet the emerging power demand of microelectronic and electronic skin based sensing platform, enzymatic fuel cells have received increasing attention due to their good human's compatibility, easy integration and cost effectiveness. Herein, we use multi-walled carbon nanotube/naphthoquinone to modify the lactate oxidase bio-anode to facilitate the electron transfer between electrocatalytic active site and electrode support. Polyvinyl alcohol hydrogel serves as the separator and lactate container. The bio-anode, Pt/C cathode and hydrogel are assembled in layer-by-layer structure, which can successfully utilize pre-stored and external lactate from human's sweat to generate the electricity. It delivers a power-density of 62.2 ± 2.4 μW cm−2 under bending/torsion conditions. Given that the broad substrate scope in sweat and easily assembled structure, it provides a plausible solution to power the miniaturized sensors and generic circuits.

A promising class of materials for applications that rely on electron transfer for signal generation are the n-type semiconducting polymers. Here we demonstrate the integration of an n-type conjugated polymer with a redox enzyme for the autonomous detection of glucose and power generation from bodily fluids. The reversible, mediator-free, miniaturized glucose sensor is an enzyme-coupled organic electrochemical transistor with a detection range of six orders of magnitude. This n-type polymer is also used as an anode and paired with a polymeric cathode in an enzymatic fuel cell to convert the chemical energy of glucose and oxygen into electrical power. The all-polymer biofuel cell shows a performance that scales with the glucose content in the solution and a stability that exceeds 30 days. Moreover, at physiologically relevant glucose concentrations and from fluids such as human saliva, it generates enough power to operate an organic electrochemical transistor, thus contributes to the technological advancement of self-powered micrometre-scale sensors and actuators that run on metabolites produced in the body. An n-type semiconducting polymer is used to realize an organic electrochemical transistor working as a glucose sensor and an all-polymer enzymatic biofuel cell able to power the sensor itself.

Miniaturization of enzymatic biofuel cell has become a crucial factor especially towards device fabrication and integrated bioelectrode system. When successful in a cost-effective manner, it can be used as a source of qualitative electric power for portable and implantable devices. The present work demonstrates the design and fabrication of cost-effective, portable, miniaturized microfluidic enzymatic biofuel cell (M-EBFC) using rapid prototyping 3D printing (3DP) technique. The low cost, radially available, non-toxic Pencil Graphite Electrodes (PGE's) were used as the electrode material. Various grades of PGE's were rigorously studied, by screening separately and cohesively for both anodic and cathodic sides, and the optimized ones (B and 5H for anodic and cathodic sides respectively) have been utilized. These PGE's successively encapsulated into Y-shaped microchannel, fabricated using a commercial 3D Printer. This platform, integrating 3D printing technology and PGE's, delivers simplistic, cost-effective and quick fabrication method, which eradicates the necessity of any further amendment and post-processing. Furthermore, the enhancement of the surface area and electrochemical sensing, PGE's were coated with carboxylated multiwalled carbon nanotube followed by the covalent immobilization enzymes. The electrochemical and polarization performance was compared between both HB and the optimized PGEs. The optimized PGE based 3D printed microfluidic membraneless enzymatic biofuel cell (3DP-MM-EBFC) showed open circuit potential (OCP) of 0.433 V and with a maximum power density of 18 μW cm−2 at a current density of 60 μA cm−2. This rapidly prototyped 3D printed fabrication technology demonstrates the viability of simple and advanced microfabrication techniques to build well-organized plug-and-play devices to power several portable low-power microelectronic devices and sensors.

This work describes EtOH,O 2 membraneless enzymatic biofuel cells (EtOH,O 2 M less EBFCs) that employ laccase-based biocathodes and ADH/NAD + bioanode. Laccase biocathodes were prepared by immobilizing a polypyrrole film containing different redox mediators (ruthenium and osmium complexes). The bioanode for EtOH,O 2 MlessEBFCs was fabricated by immobilizing multiwalled carbon nanotubes, NAD + -dependent alcohol dehydrogenase enzyme (ADH), poly-methylene green, and poly(amidoamine) (PAMAM) dendrimer onto a carbon cloth platform. Maximum power density and current density were 21.0 ± 0.2 mW cm -2 and 0.15 ± 0.07 mA cm -2 , respectively, in PBS (pH 6.5). Lifetime tests conducted for EtOH,O 2 M less EBFCs showed promising perspectives for their future application in miniaturized devices.

Enzymatic biofuel cells (EBFCs) produce electrical energy from green and renewable fuels, by utilizing redox enzyme. However, the main issue of low power output and stability of the electrode still prevails in this field. Extensive research is going on to overcome this problem by improving the electrical communication between the enzyme and the current collector. In the light of this, a new electrode design based on reduced graphene oxide (rGO) and functionalized magnetic nanoparticles (f-Fe3O4 NPs) in polyaniline matrix has been proposed and employed for the purpose of the EBFCs application, in order to achieve efficient electron shuttling between enzyme glucose oxidase (GOx) and the electrode surface. The as-prepared rGO/PANI/f-Fe3O4 nanocomposite was examined by analytical techniques viz, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the electrochemical behaviour of the rGO/PANI/f-Fe3O4 nanocomposite and rGO/PANI/f-Fe3O4/Frt/GOx bioanode was determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). The bioanode attained a maximum current density of 32.9 mA cm−2 at the optimum glucose concentration of 50 mM.

3D printing offers a novel, time-efficient, and multi-material fabrication platform for numerous applications owing to its potential to rapidly manufacture low-cost and 3D printed (3DP) structures. In this paper, polylactic acid (PLA) and conductive composite graphene/PLA filaments were used to fabricate 3DP microchannels and electrodes intended for enzymatic biofuel cells (EBFCs) using a commercial bench-top 3D printer. This 3D printing technology delivers a simplistic, cost-effective, and quick fabrication process, which eliminates the requirement of any further amendment and post-processing. With this technology, we demonstrate structurally simple, miniature 3DP microfluidic membraneless EBFCs (3DP-MM-EBFCs), served with glucose and oxygen with the utilization of redox mediators generating continuous power. The cell performance was evaluated at different flow rates, obtaining open circuit potential (OCP) 0.425 V and maximum peak power density (PD) $4.15~\mu \text{W}$ /cm2 at a current density (CD) of $13.36~\mu \text{A}$ /cm2. The advancement in 3DP electrode surface characteristic and the dimethylformamide (DMF) treatment is carried onto the electrode surface followed by the immobilization of the enzymes individually. The 3DP fabrication technology demonstrated the feasibility of simple and advanced microfabrication techniques to build a well-organized plug-and-play and rapidly analyzed device to power several portable low-power devices.

Fuel cells (FCs) have been in development for more than 50 years; whereas the application of weak output of some FCs in detection of biochemical species as self-powered electrochemical sensors (SPESs) has attracted considerable attention in past decade. Different from conventional electrochemical sensors, FC-based SPESs do not need external power supplies and complex devices, but use the electrical output as sensing signal provided by redox reactions in FCs. As a result, SPESs provide a feasible approach to the construction of miniaturized, implantable or portable devices. Different types of FCs including enzymatic biofuel cell (EBFC), microbial fuel cell (MFC) and photocatalytic fuel cell (PFC) can change their outputs with the concentration of analyte to realize the sensitive detection by using the extremely strong catalytic properties of enzymes, microorganisms and semiconducting materials, respectively. So far, SPESs have achieved some gratifying progresses through the continuous exploration of researchers. In this review, we summarize the research advances in SPESs based on three types of FCs for detection of different biochemical species, including nucleic acids, proteins, H2O2, heavy metal ions, glucose, lactate and so on. Moreover, the problems of different FCs faced for various targets and some possible solutions are proposed. Finally, we discuss the future development directions, challenges and opportunities of SPESs.

We report enzymatic biofuel cells (EBFCs) based on MgO-templated carbon (MgOC)-carbon textile composite electrodes, which are lightweight, flexible, and used as liquid containers. MgOC particles with a pore size of 40 nm were modified on a carbon cloth substrate using poly(vinylidenedifluoride) as an anodic binder and polytetrafluoroethylene as a cathodic binder. Flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) from Aspergillus terreus was used for the anode, with 1,4-naphthoquinone chosen as the redox mediator. The O2-reducing cathode contains bilirubin oxidase (BOD) from Myrocecium verucaria and 2,2′-azinobis(3-ethylbenzothiazolin-6-sulfonate) (ABTS), which facilitates electron transfer between the active site of BOD and the electrode. The hydrophobicity of the gas diffusion layer in the textile composite cathode is tuned with the aid of a PTFE binder, to increase the amount of O2 supplied from the air. The open circuit potential is 0.75 V and maximum output power density is 2 mW cm−2 at 0.4 V (room temperature, without O2 gas flow). Our results clearly indicate that MgOC-textile materials are very promising for the development of high-performance, wearable EBFCs.

Enzymatic biofuel cell (EBC) attracts much attention recently in fuel cell community because of its unique feature to enable the enzyme as a catalyst, rather than precious metal, to oxidize the fuel. However, the embedment of carbon nanotubes, commonly used in the anodic electrode of EBC to electrically wire the enzyme, suffers from their complicated synthetic procedure and fragile assembly. In this regard, we demonstrate a facile and low-cost route to achieve a desired immobilization of the glucose oxidase on a robust, flexible conducive carbon cloth. Our result indicates that the EBC using chitosan-modified carbon cloth via tripolyphosphate as anodic electrode exhibits a better performance than that via Nafion, leading to a 53% improvement of area power density. Such an enhancement can be attributed to the formation of the open porous structure on chitosan-modified carbon cloth, beneficial for the immobilization sites of the glucose oxidase and thereby facilitating more electron transfer in glucose oxidation reaction. The self-pumping EBC, driven by a capillary force of micro-fluidic channel plate, delivers an efficient area and volume power density of 0.549 mWcm−2 and 114.52 mWcm−3, respectively, enabling to open an alternative to the lightweight and portable applications.

We designed an enzymatic biofuel cell (EFC) that utilizes indium tin oxide (ITO) electrodes, and sequential deposition of single-walled carbon nanotube (SWCNT) and gold nanoparticle (AuNP) layers on the electrodes to enhance their electron transfer. Cyclic voltammograms of the SWCNT-modified ITO electrodes showed higher peak currents compared to those of the bare ITO electrodes. Immobilization of glucose oxidase (GOD) on SWCNT-modi-fied ITO electrodes increased their electron transfer resistance by a factor of ten, which could be mitigated by incorporating an AuNP layer between the GOD and SWCNT layers. The single-layer GOD generated higher current than the doubled-layer GOD, with higher specific activity. The assembled EFC featured SWCNT-modified ITO electrodes with sequential layers of immobilized AuNPs and GOD (anode), and with a single layer of immobilized bilirubin oxidase (BOD) (cathode). The cathode performance was further improved by the presence of AuNPs between the BOD and SWCNTs on cathode. The enhanced electron transfer kinetics and enzymatic activity observed for SWCNT/AuNP-modified ITO electrodes resulted in a maximum power density of 38.2±2.0 µW/cm2 at 0.57±0.03 V of a cell voltage.

Enzymatic biofuel cells (EBFCs) forms a portable source of eco-friendly energy, which can be used in different devices such as biosensors, implanted medical devices etc. Laccase a multi-copper oxidase widely used as a EBFCs cathode has a higher redox potential when compared to commercial fuel cells. For the enhancement of the electrical potential of EBFCs, good fabricating material is needed. Nano-carbons such as graphene, carbon nanotubes (CNTs), acetylene black and furnace black are excellent fabricating materials because of their low cost, higher electrical conductivity, and larger surface area. An extensive number of studies have been conducted on laccase to enhance the efficiency of the EBFC but the ultimate achievement is still anticipated. This review is intended to focus on the recent innovation in the field of laccase based EBFCs with different nanocarbons and metal nanoparticles as biocathodes, their sustainability, merits and demerits, the economic importance of EBFC.

In this study, a novel carbon tube was prepared by carbonizing a rectangular polypyrrole (RPPy) tube at a high temperature for the construction of enzymatic biofuel cells with high performance. SEM and TEM images clearly showed that the initial PPy presented a rectangular tube shape, while the carbonized PPy became a shriveled rectangular tube with a concave surface, which might be beneficial for enzyme immobilization and electrochemical applications. The glucose oxidase (GOx)- or laccase (Lac)-modified electrodes based on carbonized RPPy exhibited excellent bioelectrochemical performance. In addition, a biofuel cell (GOx, glucose/O2, Lac) was assembled, and the open-circuit voltage reached 1.16 V. The maximum power density was measured to 0.350 mW cm−2, which correlated to the gravimetric power density of 0.265 mW mg−1 (per mg of GOx) at 0.85 V. The constant-current discharge method was used to further evaluate the continuous discharge capacity. The discharge time reached 49.9 h at a discharge current of 0.2 mA before the voltage was lower than 0.8 V. Furthermore, three of the fabricated biofuel cells in series were able to continually light up a white light-emitting diode (LED) whose turn-on voltage was ca. 2.4 V for more than 48 h. This study suggests that carbonized conducting polymers may become a useful electrode material for the development of enzymatic biofuel cells.

Escherichia coli's copper efflux oxidase (CueO) has rarely been employed in the cathodic compartment of enzymatic biofuel cells (EBFCs) due to its low redox potential (0.36 V vs. Ag/AgCl, pH 5.5) towards O2 reduction. Herein, directed evolution of CueO towards a more positive onset potential was performed in an electrochemical screening system. An improved CueO variant (D439T/L502K) was obtained with a significantly increased onset potential (0.54 V), comparable to that of high-redox-potential fungal laccases. Upon coupling with an anodic compartment, the EBFC exhibited an open-circuit voltage (Voc ) of 0.56 V. Directed enzyme evolution by tailoring enzymes to application conditions in EBFCs has been validated and might, in combination with molecular understanding, enable future breakthroughs in EBFC performance.

The appearance and evolution of biofuel cells can be categorized into three groups: microbial biofuel cells (MBFCs), enzymatic biofuel cells (EBFCs), and enzyme-like nanomaterial (nanozyme)-based biofuel cells (NBFCs). MBFCs can produce electricity from waste; however, they have significantly low power output as well as difficulty in controlling electron transfer and microbial growth. EBFCs are more productive in generating electricity with the assistance of natural enzymes, but their vulnerability under diverse environmental conditions has critically hindered practical applications. In contrast, because of the intrinsic advantages of nanozymes, such as high stability and robustness even in harsh conditions, low synthesis cost through facile scale-up, and tunable catalytic activity, NBFCs have attracted attention, particularly for developing wearable and implantable devices to generate electricity from glucose in the physiological fluids of plants, animals, and humans. In this review, recent studies on NBFCs, including the synthetic strategies and catalytic activities of metal and metal oxide-based nanozymes, the mechanism of electricity generation from glucose, and representative studies are reviewed and discussed. Current challenges and prospects for the utilization of nanozymes in glucose biofuel cells are also discussed.

Enzymatic biofuel cells (EBFCs) are known as sustainable energy sources due to the utilization of renewable enzyme biocatalysts and fuels, together with mild working conditions. Remarkably, their novel and interesting applications in the fields of implantable energy supply devices and self‐powered biosensor are born and attract extensive attention worldwide. But the transition from fundamental research to practical application is problematic due to low efficiency, poor durability, tricky miniaturization, and so on. So, in addition to a detailed review, whether the full potential of these novel EBFCs‐based applications can be implemented will be clearly stated herein as well. More importantly, the emergences of EBFCs‐based self‐powered therapy systems and EBFCs‐based artificial organ open up more possibilities for the future EBFCs. Such remarkable directions and opportunities of EBFCs will also be prospected in detail.

Enzymatic biofuel cells (EBFCs) is one of the branches of fuel cells that can provide high potential for various applications. However, EBFC has challenges in improving the performance power output. Exploring electrode materials is one way to increase enzyme utilization and lead to a high conversion rate so that efficient enzyme loading on the electrode surface can function correctly. This paper briefly presents recent technologies developed to improve bio-catalytic properties, biocompatibility, biodegradability, implantability, and mechanical flexibility in EBFCs. Among the combinations of materials that can be studied and are interesting because of their properties, there are various nanoparticles, carbon-based materials, and conductive polymers; all three have the advantages of chemical stability and enhanced electron transfer. The methods to immobilize enzymes, and support and substrate issues are also covered in this paper. In addition, the EBFC system is also explored and developed as suitable for applications such as self-pumping and microfluidic EBFC.

Here, a low-cost glucose/O2 Y-shaped microfluidic biofuel cell was developed using a printed circuit board for microelectrode construction. A double-side tape based on the pressure-sensitive adhesive was used for microchannel fabrication. A nanocomposite that consisted of reduced graphene oxide gold nanoparticles (AuNPs), and poly neutral red connected to enzymes was applied on the copper electrode surface. The Aspergillus niger glucose oxidase enzyme and Mytheliophthora thermophile laccase were used to prepare the modified anodic and cathodic electrodes. Different procedures such as cyclic voltammetry scanning electron microscope coupled with energy-dispersive x-ray spectroscopy (EDX), and atomic force microscopy were used to scan the modified electrodes. SEM/EDX microanalysis displayed the structural and morphological properties of the proposed nanocomposite. The biofuel cell performance demonstrated a maximum power density of 36 μW cm−2, an open-circuit voltage of 0.5 V, and a flow rate of 50 μl min−1. The proposed rapid technique with RGO/AuNPs/PNR bioelectrodes is a good approach for finding low-cost microfluidic biofuel cells.

Direct electron transfer (DET) of enzymes on electrode surfaces is highly desirable both for fundamental mechanistic studies and to achieve membrane- and mediator-less bioenergy harvesting. In this report, we describe the preparation and comprehensive structural and electrochemical characterization of a three-dimensional (3D) graphene-based carbon electrode, onto which the two-domain redox enzyme Myriococcum thermophilum cellobiose dehydrogenase (MtCDH) is immobilized. The electrode is prepared by an entirely novel method, which combines in a single step electrochemical reduction of graphene oxide (GO) and simultaneous electrodeposition of positively charged polyethylenimine (PEI), resulting in a well dispersed MtCDH surface. The resulting MtCDH bio-interface was characterized structurally in detail, optimized, and found to exhibit a DET maximum current density of 7.7 ± 0.9 μA cm−2 and a half-lifetime of 48 h for glucose oxidation, attributed to favorable MtCDH surface orientation. A dual, entirely DET-based enzymatic biofuel cell (EBFC) was constructed with a MtCDH bioanode and a Myrothecium verrucaria bilirubin oxidase (MvBOD) biocathode. The EBFC delivers a maximum power density (Pmax) of 7.6 ± 1.3 μW cm−2, an open-circuit voltage (OCV) of 0.60 V, and an operational lifetime over seven days, which exceeds most reported CDH based DET-type EBFCs. A biosupercapacitor/EBFC hybrid was also constructed and found to register maximum power densities 62 and 43 times higher than single glucose/air and lactose/air EBFCs, respectively. This hybrid also shows excellent operational stability with self-charging/discharging over at least 500 cycles.

Because of environmental concerns, there is a growing interest in new ways to produce green energy. Among the several studied applications, enzymatic biofuel cells can be considered as a promising solution to generate electricity from biological catalytic reactions. Indeed, enzymes show very good results as biocatalysts thanks to their excellent intrinsic properties, such as specificity toward substrate, high catalytic activity with low overvoltage for substrate conversion, mild operating conditions like ambient temperature and near-neutral pH. Furthermore, enzymes present low cost, renewability and biodegradability. The wide range of applications moves from miniaturized portable electronic equipment and sensors to integrated lab-on-chip power supplies, advanced in vivo diagnostic medical devices to wearable devices. Nevertheless, enzymatic biofuel cells show great concerns in terms of long-term stability and high power output nowadays, highlighting that this particular technology is still at early stage of development. The main aim of this review concerns the performance assessment of enzymatic biofuel cells based on flow designs, considered to be of great interest for powering biosensors and wearable devices. Different enzymatic flow cell designs are presented and analyzed highlighting the achieved performances in terms of power output and long-term stability and emphasizing new promising fabrication methods both for electrodes and cells.

In this article, we describe an enzyme-based, membraneless, microfluidic biofuel cell for the continuous determination of glucose using electrochemical power generation as a transducing signal. Enzymes were immobilized on multi-walled carbon nanotube (MWCNT) electrodes placed parallel to the co-laminar flow in a Y-shaped microchannel. The microchannel was produced with polydimethylsiloxane (PDMS) using soft lithography, while the MWCNT electrodes were replicated via a PDMS stencil on indium tin oxide (ITO) glass. Moreover, the electrodes were modified with glucose oxidase and laccase by direct covalent bonding. The device was studied at different MWCNT deposition amounts and electrolyte flow rates to achieve optimum settings. The experimental results demonstrated that glucose could be determined linearly up to a concentration of 4 mM at a sensitivity of 31 mV∙mM&minus, 1cm&minus, 2.

Enzymatic biofuel cells (EBFCs) have excellent potential as components in bioelectronic devices, especially as active biointerfaces to regulate stem cell behavior for regenerative medicine applications. However, it remains unclear to what extent EBFC-generated electrical stimulation can regulate the functional behavior of human adipose-derived mesenchymal stem cells (hAD-MSCs) at the morphological and gene expression levels. Herein, we investigated the effect of EBFC-generated electrical stimulation on hAD-MSC cell morphology and gene expression using next-generation RNA sequencing. We tested three different electrical currents, 127 &plusmn, 9, 248 &plusmn, 15, and 598 &plusmn, 75 nA/cm2, in mesenchymal stem cells. We performed transcriptome profiling to analyze the impact of EBFC-derived electrical current on gene expression using next generation sequencing (NGS). We also observed changes in cytoskeleton arrangement and analyzed gene expression that depends on the electrical stimulation. The electrical stimulation of EBFC changes cell morphology through cytoskeleton re-arrangement. In particular, the results of whole transcriptome NGS showed that specific gene clusters were up- or down-regulated depending on the magnitude of applied electrical current of EBFC. In conclusion, this study demonstrates that EBFC-generated electrical stimulation can influence the morphological and gene expression properties of stem cells, such capabilities can be useful for regenerative medicine applications such as bioelectronic devices.

The potential application of biodevices based on enzymatic bioelectrocatalysis are limited by poor stability and electrochemical performance. To solve the limitation, modifying enzyme with functional polymer to tailor enzyme function is highly desirable. Herein, glucose oxidase (GOx) was chosen as a model enzyme, and according to the chemical structure of GOx cofactor (flavin adenine dinucleotide, FAD), we customize a biomimetic cofactor containing vinyl group (SFAD) for GOx, and prepared an GOx nanocapsule via in-situ polymerization. The characterization of particle size distribution, TEM, fluorescence and electrochemical performance indicated the successful formation of electroactive GOx nanocapsule with SFAD-containing polymeric network (n (GOx-SFAD-PAM)). The network can act as an electronic “highway” to link the active site with electrode, with capability to accelerate electron transfer as well as enhanced GOx stability. Further investigation of bioelectrocatalysis shows that n (GOx-SFAD-PAM)-based biosensor has low detection potential (−0.4 vs. Ag/AgCl), high sensitivity (64.97 μAmM−1cm−2), good anti-interference performance, quick response (3⁓5s) and excellent stability, and that n (GOx-SFAD-PAM)-based enzymatic biofuel cell (EBFC) has the high maximum power density (1011.21 μWcm−2), which is a 385-fold increase over that of native GOx-based EBFC (2.62 μWcm−2). This study suggests that novel enzyme nanocapsule with electroactive polymeric shell might provide a prospective solution for the performance improvement of enzymatic bioelectrocatalysis-based biodevices.

Animals digest food to fuel brain neurometabolism via cellular respiration. This study demonstrates the combination of a biofuel cell (BFC) and an animal brain stimulator (ABS) implanted in a pigeon. Glucose oxidation and oxygen reduction in an enzymatic BFC supplied electrical power to the ABS. Power from the BFC reached 0.12 mW in vitro and 0.08 mW in vivo using only the natural glucose and oxygen in the pigeon's body. A power management integrated circuit is used to harvest energy from the in vivo BFC at a rate of 28.4 mJ over 10 min, which is sufficient for intermittent neurostimulation.

Glutathione is an important biological molecule which can be an indicator of numerous diseases. A method for self-powered detection of glutathione levels in solution has been developed using an enzymatic biofuel cell. The device consists of a glucose oxidase anode and a bilirubin oxidase cathode. For the detection of glutathione, the inhibition of bilirubin oxidase leads to a measurable decrease in current and power output. The reported method has a detection limit of 0.043 mM and a linear range up to 1.7 mM. Being able to detect a range of concentrations can be useful in evaluating a patient&rsquo, s health. This method has the potential to be implemented as a quick, low-cost alternative to previously reported methods.