Search

Wearable sweat sensors combine the benefits of noninvasive sweat sampling and wearable real-time measurement, providing a powerful platform for monitoring a wealth of biochemical components of sweat related to physiological conditions. The recent progress of wearable sweat sensors is attributed to the rapid development of interdisciplinary research among material science, manufacturing technology, and advanced electronics field. This review focuses on the construction of wearable sweat sensors, especially the design of a flexible sensing interface and integrated wearable sweat sensor. In addition, we outline the extensive applications of wearable sweat sensors from healthcare and sports monitoring to biofuel cells. Finally, several issues and opportunities of future wearable sweat sensors are discussed.

The implanted electronic devices require a stable, continuous, and long-lasting energy source to function correctly. These devices are powered by alkaline batteries and lithium ions. When used in implantable or wearable devices, these batteries can pose a threat to human health and the environment. Because of these factors, implantable and wearable devices using enzyme biofuel cells (EBFCs) are receiving a lot of attention. These EBFCs use human physiological fluid to provide long-term control for these devices. Carbon nanomaterials have successfully been demonstrated in enzymatic biofuel cells to improve applications by increasing current and power density; they have the potential to enhance EBFC efficiency. This review summarizes the fundamental process of EBFC compounds based on carbon nanomaterials before delving into the most recent advancements that have been tested and used as implantable and wearable self-power sources.

Extensive use of Unmanned Underwater Vehicles (UUVs) and remote equipment in future Naval operations leads to an energy logistics challenge for their rechargeable batteries. A solution to this challenge is a distributed network of renewable power sources detached from mainland power grids. One potential solution is Benthic Microbial Fuel Cell (BMFC) devices. BMFCs must be optimized and upscaled to produce power at relevant scales. 3-D printing is a promising manufacturing method to achieve scalable BMFC devices. In this thesis, we devised, developed, and optimized a protocol for clearance of microfluidic channels using square cross-sections embedded within PolyJet 3-D-printed chips. The developed protocol demonstrated 75% volumetric clearance of the embedded channels. The protocol was then used to clear channels with T-shaped cross-sections, which were used to produce an experimental proof of principle for self-assembled wiring within the microchannels due to fluidic surface tension. These advancements have opened the door to embedded wiring for 3-D printed biofuel cells and other microfluidic technologies. When perfected and manufactured at scale, biofuel cells could provide a solution to the critical logistics problem of recharging UUVs and similar equipment employed in remote maritime environments, thereby making an exceptional contribution to the U.S. Navy, U.S. national security, and the related research fields. Office of Naval Research, Arlington, VA 22203 Lieutenant, United States Navy Approved for public release. Distribution is unlimited.

Sweat could be a carrier of informative biomarkers for health status identification; therefore, wearable sweat sensors have attracted significant attention for research. An external power source is an important component of wearable sensors, however, the current power supplies, i.e., batteries, limit further shrinking down the size of these devices and thus limit their application areas and scenarios. Herein, we report a stretchable self-powered biosensor with epidermal electronic format that enables the in situ detection of lactate and glucose concentration in sweat. Enzymatic biofuel cells serve as self-powered sensing modules allowing the sweat sensor to exhibit a determination coefficient (R2) of 0.98 with a sensitivity of 2.48 mV/mM for lactate detection, and R2 of 0.96 with a sensitivity of 0.11 mV/μM for glucose detection. The microfluidic channels developed in an ultra-thin soft flexible polydimethylsiloxane layer not only enable the effective collection of sweat, but also provide excellent mechanical properties with stable performance output even under 30% stretching. The presented soft sweat sensors can be integrated at nearly any location of the body for the continuous monitoring of lactate and glucose changes during normal daily activities such as exercise. Our results provide a promising approach to develop next-generation sweat sensors for real-time and in situ sweat analysis.

Thanks to rapid technological innovation over the last decade, a wide range of wearable devices have emerged, playing an inspiring role in healthcare, diagnostics, and sports monitoring. This review summarizes recent progress in the development and application of electrochemical (EC) sweat sensors and self-powered systems for wearable applications. Presented here are the most common types of EC sweat sensors, namely potentiometric ion-selective electrodes, amperometric enzymatic and non-enzymatic sensors, as well as differential pulse voltammetric sensors. The sensing principle and novel functional nanomaterials that are used to enhance the performance of wearable sweat sensors and their applications are summarized. The recent advancement of battery-free wearable devices is presented, including self-powered biofuel cells (BFC), energy harvesting from novel materials and its strategy, are also discussed. The challenges in, and opportunities for, the development of sweat sensor-based wearable systems moving forward are reviewed, with the aim of shedding some light on future directions.

Many healthcare and environmental monitoring devices use electrochemical techniques to detect and quantify analytes. With sensors progressively becoming smaller-particularly in point-of-care (POC) devices and wearable platforms-it creates the opportunity to operate them using less energy than their predecessors. In fact, they may require so little power that can be extracted from the analyzed fluids themselves, for example, blood or sweat in case of physiological sensors and sources like river water in the case of environmental monitoring. Self-powered electrochemical sensors (SPES) can generate a response by utilizing the available chemical species in the analyzed liquid sample. Though SPESs generate relatively low power, capable devices can be engineered by combining suitable reactions, miniaturized cell designs, and effective sensing approaches for deciphering analyte information. This review details various such sensing and engineering approaches adopted in different categories of SPES systems that solely use the power available in liquid sample for their operation. Specifically, the categories discussed in this review cover enzyme-based systems, battery-based systems, and ion-selective electrode-based systems. The review details the benefits and drawbacks with these approaches, as well as prospects of and challenges to accomplishing them., Advanced Science, 9 (29), ISSN:2198-3844

Enzyme cascades are plentiful in nature, but they also have potential in artificial applications due to the possibility of using the target substrate in biofuel cells, electrosynthesis, and biosensors. Cascade reactions from enzymes or hybrid bioorganic catalyst systems exhibit extended substrate range, reaction depth, and increased overall performance. This review addresses the strategies of cascade biocatalysis and bioelectrocatalysis for ( a) CO2 fixation, ( b) high value-added product formation, ( c) sustainable energy sources via deep oxidation, and ( d) cascaded electrochemical enzymatic biosensors. These recent updates in the field provide fundamental concepts, designs of artificial electrocatalytic oxidation-reduction pathways (using a flexible setup involving organic catalysts and engineered enzymes), and advances in hybrid cascaded sensors for sensitive analyte detection.

Acidophilic chemolithotrophic microorganisms are used in biohydrometallurgy for the extraction of metals from sulphide ores. Some types of microorganisms belonging to this group are capable of generating electricity under certain conditions. This circumstance determined a recent upsurge of research interest in their use in biofuel cells. Under a constant supply of the substrate to the bioelectrochemical system, acidophilic chemolithotrophic microorganisms are capable of producing electricity for a prolonged period of time. The use of extremophiles in microbial fuel cells is of particular interest, since these microorganisms can serve as bioelectrocatalysts at extreme pH, salinity and temperature, while the vast majority of microorganisms are unable to survive under these conditions. Therefore, selection of optimal conditions and approaches to controlling the work of acidophilic chemolithotrophic microorganisms in such fuel cells is of particular importance. On this basis, a technology for the simulteneous bioleaching of metals from poor ores and the generation of electricity can be developed. Biofuel cells operating at low pH values using acidophilic chemolithotrophic microorganisms are yet to be investigated. The number of studies on acidophilic electroactive microorganisms is very limited. In this regard, the purpose of this review was to consider the prospects for the use of acidophilic chemolithotrophic microorganisms as bioagents in microbial fuel cells. The reviewed publications demonstrate that chemolithotrophic microorganisms can act as both anodic (metal-reducing, sulphur-oxidizing microorganisms) and cathodic (metal-oxidizing prokaryotes, sulfate reducers) highly efficient bioagents capable of using mining wastes as substrates.

The bioelectrochemical and spectral properties of immobilized Gluconacetobacter sucrofermentas VKPM B-11267 bacteria were studied in the presence and absence of multiwalled carbon nanotubes (MWCNTs). The obtained characteristics were compared with the characteristics of Gluconobacter oxydans, which are phylogenetically close to them and are widely used in bioelectrochemistry. It was shown that modification of the bioelectrode with carbon nanotubes leads to a significant increase in the current level (by 2.5–3 times), as well as to a decrease in the total resistance both in the absence of substrates and in their presence. The potential use of immobilized G. sucrofermentas cells as part of a microbial fuel cell (MFC) was considered. The specific electrical power of an MFC based on immobilized G. sucrofermentas cells was lower than that of an MFC based on G. oxydans cells. Nevertheless, the results obtained indicate that G. sucrofermentas VKPM B-11267 cells can serve as a biocatalyst in MFCs.

Exploiting electrocatalysis for wearable enzyme-free biosensors and biofuel cells has recently greatly developed in preliminary medical diagnosis and human healthcare fields. Herein, several facet-...

Enzyme centered biofuel cells became the center of focus for various researchers recently owing to their wide spread applications on several fields. During the current times, experimental research has been widely conducted in applications like biosensor and biofuel cell that contains enzyme electrodes. The interest in developing enzyme modified electrodes for biofuel cells increases rapidly because of the flourishment of healthcare applications that utilizes more number of medical devices for implantation. This review considers the literature on enzymatic electrodes for biofuel cells. Normally nano-carbons are used for manufacturing of enzyme-modified electrodes for biofuel cells owing to their large specific surface area. The stability of these enzyme-modified bio-electrodes becomes an significant parameter in measuring the biofuel cell life time.

Due to the increasing demand for monitoring diseases such as rising heart rate, diabetes, and ocular disorders wearable and implantable biomedical devices seems too essential for patients not only in the hospital but also at home or during working time. Researchers mostly try to offer valuable information on the conditions of patients as non-invasive, by using comfort biomedical device with a minimum side effect. So, small and self-powered with high sensitivity biomedical devices are recommended, among different power sources that introduced for devices, biofuel cells would be produced as power source for a range of medical devices because of its capability to generate sufficient power output compared to the primary power source. The nature of the electrode reaction and the nature of the biochemical reactions are some of the important parameters that are considered for the classification of fuel cells. Enzymatic biofuel cells due to high activity at mild conditions widely applied in pacemaker; glucometer; and smart contact lenses when compared to other kinds of biofuel cells. On the other hand, short lifespan is one of important limitations in this type of biofuel cells. So, the easiest way to overcome these challenges is to apply non-enzymatic ones. Recent studies have attempted to issue novel method for fabrication of non-enzymatic biofuel cell in order to produce a new generation which are inexpensive, disposable, selective, and sensitive in properties. However, consideration of researchers to the development of self-powered biomedical devices by using body fluids or providing electricity storage is rising.

Bio-electroactive fuel cells are systems that produce useful products from renewable sources without causing environmental pollution and treating waste. In this study, general design properties, operation mechanisms, application areas, and historical advancement of the bio-electroactive fuel cell was reviewed. Electricity generating microbial fuel cells offer new opportunities as with hydrogen and methane-producing microbial electrolysis cells due to their attractive variety of electroactive microorganisms and operating situations. This article provides an up-to-date review for Bio-electroactive fuel cells and outlines instructions for future studies.

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...

This review deals with the use of the highly conductive polymer PEDOT:PSS in biomedical and bioelectrochemical systems. The examples of toxic effects on living cells, positive effects of PEDOT:PSS on the viability of cells and tissues are given. The properties of the polymer, methods of increasing its electrical conductivity by its modification with various nanoparticles and nanomaterials are discussed. Examples of using PEDOT and its composites in bioelectrochemical devices, such as biosensors and biofuel cells, are considered. Changes in the characteristics of biosensors and biofuel cells under the influence of PEDOT are discussed.

We report on a photobioelectrochemical fuel cell consisting of a glucose‐oxidase‐modified BiFeO3 photobiocathode and a quantum‐dot‐sensitized inverse opal TiO2 photobioanode linked to FAD glucose dehydrogenase via a redox polymer. Both photobioelectrodes are driven by enzymatic glucose conversion. Whereas the photobioanode can collect electrons from sugar oxidation at rather low potential, the photobiocathode shows reduction currents at rather high potential. The electrodes can be arranged in a sandwich‐like manner due to the semi‐transparent nature of BiFeO3, which also guarantees a simultaneous excitation of the photobioanode when illuminated via the cathode side. This tandem cell can generate electricity under illumination and in the presence of glucose and provides an exceptionally high OCV of about 1 V. The developed semi‐artificial system has significant implications for the integration of biocatalysts in photoactive entities for bioenergetic purposes, and it opens up a new path toward generation of electricity from sunlight and (bio)fuels., A photobioelectrochemical tandem cell is presented in which two photoelectrodes have been functionally coupled with two biocatalysts for supplying the light‐driven reaction with charge carriers from glucose conversion. The cell allows the generation of electricity from biofuels and light with a high open‐circuit voltage of 1 V.

Photoelectrochemical biofuel cells can convert light and chemical energy into electrical energy using a dye-sensitized titania (TiO2) fluorine-doped tin oxide photoanode and a platinum-coated fluorine-doped tin oxide cathode. TiO2 of the photoanode serves both as a support for dyes and as an electron-transporting medium, the structure of which can limit electron trapping and charge transporting and then affect the performance of the photoelectrochemical biofuel cells. TiO2 nanotube array films have been shown to enhance the efficiencies of both charge collection and electron injection, and hence a vertically aligned TiO2 nanotube array is investigated as a conductor for the tetrakis(4-carboxyphenyl)porphyrin dye to construct a new two-compartment photoelectrochemical biofuel cell. The photoelectrochemical biofuel cell containing the TiO2 nanotube array photoanode yields a short-circuit (Isc) current of 110 μA and an open-circuit (Voc) potential of 1010 mV. In contrast, the photovoltaic parameters, Isc and Voc of the photoelectrochemical biofuel cell with the mesoporous TiO2 nanocrystal fluorine-doped tin oxide photoanode, are 96.96 μA and 740 mV, respectively. Photovoltaic measurements show that the maximum incident photon-to-collected electron conversion efficiency was 58% at 430 nm through the spectral range (400–800 nm) for the photoelectrochemical biofuel cell with the TiO2 nanotube array fluorine-doped tin oxide photoanode. These results revealed that the TiO2 nanotube array had great potential for the photoelectrochemical biofuel cells.

Black phosphorus (BP) has attracted tremendous attention as a new two-dimensional semiconductor material with excellent optical and electrical properties. Unfortunately, the mimicking enzyme charac...

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...

Variants of the highly active [NiFeSe] hydrogenase from D. vulgaris Hildenborough that exhibit enhanced O2 tolerance were used as H2‐oxidation catalysts in H2/O2 biofuel cells. Two [NiFeSe] variants were electrically wired by means of low‐potential viologen‐modified redox polymers and evaluated with respect to H2‐oxidation and stability against O2 in the immobilized state. The two variants showed maximum current densities of (450±84) μA cm−2 for G491A and (476±172) μA cm−2 for variant G941S on glassy carbon electrodes and a higher O2 tolerance than the wild type. In addition, the polymer protected the enzyme from O2 damage and high‐potential inactivation, establishing a triple protection for the bioanode. The use of gas‐diffusion bioanodes provided current densities for H2‐oxidation of up to 6.3 mA cm−2. Combination of the gas‐diffusion bioanode with a bilirubin oxidase‐based gas‐diffusion O2‐reducing biocathode in a membrane‐free biofuel cell under anode‐limiting conditions showed unprecedented benchmark power densities of 4.4 mW cm−2 at 0.7 V and an open‐circuit voltage of 1.14 V even at moderate catalyst loadings, outperforming the previously reported system obtained with the [NiFeSe] wild type and the [NiFe] hydrogenase from D. vulgaris Miyazaki F., Triple protection: A stable, high‐current‐density‐based H2‐oxidation bioanode is presented. It is equipped with [NiFeSe] variants that show enhanced O2 tolerance, which are immobilized and wired to electrode surfaces with a low‐potential viologen‐modified polymer. The polymer acts simultaneously as a high‐potential and O2 shield. The triply protected bioanodes are incorporated in membrane‐free biofuel cells, which reveal benchmark performances at moderate catalyst loading.

Важным направлением в области медицинской техники является создание имплантируемых устройств, поддерживающих функционирование организма. Многие из таких устройств требуют энергоснабжения, причем желательно, чтобы такие источники работали весь период имплантации, даже если речь идет о пожизненной установке импланта. Представлен обзор литературных данных по источникам энергии для питания имплантируемых и носимых медицинских устройств. Приведена сравнительная оценка характеристик биотопливных элементов как наиболее проработанного варианта имплантируемого источника энергии с другими возобновляемыми источниками электрической энергии на основе термо-, пьезо-, электростатических, магнито- и фотопреобразователей. Особое внимание уделено применению имплантируемых устройств, которые могут служить источником энергии для маломощных потребителей – микропомп, кардиостимуляторов, нейроимплантов и т.д.

Glucose oxidase (GOx) is one of the most widely investigated enzymes in the field of bioelectrochemistry. It is mainly used for the detection of glucose in solutions and enzyme-based biofuel cells. On the basis of the combination of GOx with graphene, novel nanodevices exceeding conventional limits can be developed. To develop a hybrid enzyme-graphene nanodevice with a good performance, it is important that GOx is deposited well on the graphene surface while maintaining its structure and not impeding the oxidation activity of the GOx. In this study, we propose a method to improve the stability of GOx and secure its immobility on the graphene sheet and its glucose-binding affinity by single-point mutation of GOx using molecular dynamics simulations. We confirm that the structural stability, immobility, and substrate binding affinity of GOx can be modified by changing the hydrophobicity of a key residue. We demonstrate that biosensors or biofuel cells can be redesigned and their properties can be improved by using molecular dynamics simulation.

Transient energy supply remains one of the key challenges limiting the development of transient implantable medical devices for monitoring, diagnosis, and treatment of diseases within a predetermined time frame. A key feature of such devices is their controllable degradation during service life. An on-board transient energy supply with predictable performance over time is required to drive transient electronics. In this article, we present recent advances in the development of materials for biodegradable energy-storage devices (batteries and supercapacitors) and biodegradable energy-harvesting systems (enzymatic biofuel cells and triboelectric nanogenerators). Future perspectives, challenges, and opportunities related to energy materials for transient power sources will also be summarized.

Various methods of immobilizing enzymes on electrodes have been developed for the research of enzymatic biofuel cells (EBFCs). Among these methods, the layer-by-layer (LbL) assembly is a delicate technology that can form controllable enzyme layers and load a high density of enzyme molecules by electrostatic deposition, hydrogen bonding, or covalent bonding. In this paper, recent advancements of the LbL assembly for immobilizing enzymes in EBFCs are presented in detail. First, the LbL formation mechanism of a multilayer sensitive film on electrodes is analyzed, and the potential of the multilayer structure is also discussed. Then, the applications of enzyme immobilization by the LbL assembly in combination with various materials in EBFCs are investigated. The power density of LbL assembly-based EBFCs increases by several orders of magnitude with the widespread use of nanomaterials. As a convenient and efficient operation, the LbL assembly technology is expected to become a popular method for immobilizing enzymes in EBFCs.

Biofuel cells involving enzymes and whole cells of microorganisms are gaining interest with the increasing need for self-powered devices. Their nontoxic, pollution-free energy conversion technology has received tremendous attention in the last two decades, evidenced by the existing literature on this field. There are also various reviews explaining the developments of microbial fuel cells. Biofuel cells can convert a wide range of substrates from sustainable sources to electrical power and could have a promising prospect of contributing to future energy requirements. However, this technology needs steady exploration to lead it toward technology readiness. In this chapter, we focus on the recent developments in the area of biofuel cells with respect to enzymatic and microbial fuel cells, along with their future aspects leading to develop a promising technology for mankind.

This chapter introduces polymer membranes used in microbial fuel cells (MFCs), beginning with a brief introduction on biofuel cells. Following the same, it focuses on membrane properties and characterizations. Ion exchange membranes, particularly cation exchange membrane (CEM) used in MFC performance, are elucidated. Polymer membranes categorized into polymer-polymer composites, metal-based nano polymer composites and carbon-polymer composites including recent advances of the same are elaborated. A short review on membrane-free MFC is also discussed. The chapter concludes with other potential uses of MFC.

Polydopamine (PDA), formed by self-polymerizing dopamine, is coated over a lactate oxidase (LOx)- and 1,2-naphthoquinone-modified MgO-template carbon electrode to improve electrode stability. After...

An efficient immobilization of Glucose oxidase (GOx) on an appropriate substrate is one of the main challenges of developing fuel cells that allow energy to be obtained from renewable substrates such as carbohydrates in physiological environments. The research importance of biofuel cells relies on their experimental robustness and high compatibility with biological organisms such as tissues or the bloodstream with the aim of obtaining electrical energy even from living systems. In this work, we report the use of 5,10,15,20 tetrakis (1-methyl-4-pyridinium) porphyrin and glutathione capped CdTe Quantum dots (GSH-CdTeQD) as a support matrix for the immobilization of GOx on carbon surfaces. Fluorescent GSH-CdTeQD particles were synthesized and their characterization by UV-Vis spectrophotometry showed a particle size between 5–7 nm, which was confirmed by DLS and TEM measurements. Graphite and Toray paper electrodes were modified by a drop coating of porphyrin, GSH-CdTeQD and GOx, and their electrochemical activity toward glucose oxidation was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Additionally, GOx modified electrode activity was explored by scanning electrochemical microscopy, finding that near to 70% of the surface was covered with active enzyme. The modified electrodes showed a glucose sensitivity of 0.58 ± 0.01 μA/mM and an apparent Michaelis constant of 7.8 mM. The addition of BSA blocking protein maintained the current response of common interferent molecules such as ascorbic acid (AA) with less than a 5% of interference percentage. Finally, the complex electrodes were employed as anodes in a microfluidic biofuel cell (μBFC) in order to evaluate the performance in energy production. The enzymatic anodes used in the μBFC allowed us to obtain a current density of 7.53 mAcm−2 at the maximum power density of 2.30 mWcm−2; an open circuit potential of 0.57 V was observed in the biofuel cell. The results obtained suggest that the support matrix porphyrin and GSH-CdTeQD is appropriate to immobilize GOx while preserving the enzyme’s catalytic activity. The reported electrode arrangement is a viable option for bioenergy production and/or glucose quantification.

This review article focusses on new advances in the field of enzyme fuel cells (EFCs), especially, on flexible materials which can be used to make flexible EFCs for wearable devices, three-dimensional (3D) printed structures to prepare electrodes for EFCs and micro/nano electromechanical structures (MEMS/NEMS) to fabricate micro-EFCs. Particular attention is given to newly developed approaches to obtain efficient electrodes for harvesting energy via EFCs. This review article explains the various attributes of these recently developing technologies and their ability to mitigate the energy requirements of flexible/wearable bioelectronic devices. Besides discussing key milestones achieved, this perspective review article also emphasizes the main hurdles that are currently impeding the realization of flexible/wearable EFCs. We have also emphasized on the major hurdles related to the flexible materials required to fabricate wearable EFCs, suitable 3D printing techniques required, and MEMS and NEMS to fabricate micro-EFCs. In all the recently developed techniques, there are some common issues like stability, low power output, mechanical strength and flexibility. This review article also provides various routes to mitigate these issues. The main aim of this perspective article is to develop curiosity among the researchers of various fields to team up in order to address the huge challenges that restrict the real-world application of flexible/wearable EFCs. Such collaboration is important to harness the full potential of EFCs. It is requested to read this review article with supporting information to get the complete essence.

Protonic ceramic fuel cell (PCFC) is an all ceramic oxide fuel cell, but different from SOFC, protons rather than oxygen ions are going through the ceramic oxide electrolyte. Due to the high mobility of protons, PCFC offers promising potential as efficient fuel cells at low temperatures of 300–600 oC. This Chapter will give an overview of the principle, protonic ceramic electrolyte and electrode materials of PCFC. For highly efficient PCFCs, it is necessary to develop cathode materials with oxide ion, protonic and electronic conductivity, or triple conducting oxides (TCO) for oxygen reduction reaction. Finally some important and emerging fuel cells are briefly introduced, including microbial fuel cells (MFCs), and biofuel cells (BFCs).