Enzymatic Glucose Biofuel Cell Research Articles

Microfluidic carbon cloth-based enzymatic glucose biofuel cell for sustainably powering a microelectronic circuit *

Enhancing enzymatic microfluidic biofuel cells (EBFCs) devices has garnered significant attention due to the development of microfluidic ultra-low power energy-gathering techniques. To facilitate the ability to create microfluidic EBFCs, a carbon cloth (CC) has been considered since they are effective renewable energy sources and utilized as the ideal paper-based substitute for traditional power supplies for a variety of tiny devices due to their inherent qualities and exceptional performance. The developed microfluidic EBFC utilized glucose as a fuel, carbon cloth as the bioelectrode, Glucose oxidase for the anode, and laccase for the cathode. The maximum stable open circuit voltage of CC-EBFC was measured to be 475 mV with a peak power density of 85 µW cm−2 at 300 mV and a current density of 484 µA cm−2. The power performance of the device was improved by bovine serum albumin and a booster circuit, which was also coated and connected to the load to stabilize the performance. The novelty of the work is that using a flexible substrate of carbon cloth, with a microfluidic channel, has an added advantage in the biofuel cell. LTC3108EDE DC–DC booster was used to increase energy and attain a high charging voltage of 5 V to operate a digital watch up to 3 V. With minimal weight and flexibility; this minuscule device opens up new possibilities to sustainably power wearable and portable microelectronic devices.

Monolayer textile-based co-laminar flow biocompatible enzymatic biofuel cell

In this study, a body-friendly textile-based enzymatic glucose biofuel cell, which is applicable to wearable electronics, was developed. The microchannel of the biofuel cell was patterned by silk screen printing using Ecoflex. To develop this body-friendly wearable enzymatic fuel cell, a bi-enzyme system composed of glucose oxidase-catalase and glucose oxidase-horseradish peroxidase was applied to the anode and cathode, respectively. The catholyte mixed with glucose was saturated with O2 to enhance the fuel cell performance. The cell performance was affected by concentrations of enzyme biocatalyst and glucose. The best performance of the newly developed fuel cell was the peak power density of 43.6 ± 1.97 μW cm−2. The fuel cell was tested in an electrolyte physiological condition, and its power density was reduced to 25 %. Compared to the paper-based enzymatic fuel cell, the power density was approximately 11 % lower; however, the duration (11 h) was significantly longer. The performance of the proposed fuel cell was slightly lower than that of traditional enzymatic biofuel cells. Nevertheless, it is expected that the proposed body-friendly enzymatic biofuel cell has future promise as a power source for flexible bioelectronics.

Cherry-like Pt@Fe3O4 decorated MWCNT/PANI nanohybrid based bioanode for glucose biofuel cell application

With the tremendous research in enzymatic biofuel cells, development of high-performance hybrid nanocomposites to serve as effective immobilization supports for oxido-reductive enzymes is of paramount importance. These nanocomposite based electrocatalysts are being extensively explored as low-cost solutions in enzymatic glucose biofuel cells to address the challenges of instability, short-lifetime, and poor electron transfer. Herein, a hybrid nanocomposite was synthesized by insitu polymerization of polyaniline (PANI) which is composed of multiwalled carbon nanotubes (MWCNTs) and platinum nanoparticles (Pt NPs) decorated on magnetite (Fe3O4) nanosphere with cherry like morhology. This study presents a facile and cost-effective Pt@Fe3O4/MWCNT/PANI nanoelectrocatalyst effective for the immobilization of glucose oxidase (GOx) and for exhibiting outstanding electrocatalytic activity by mediated electron transfer harvesting energy from glucose oxidation. The Pt@Fe3O4/MWCNT/PANI nanohybrid based enzymatic glucose biofuel cell demonstrated a maximum current density of 7.3 mA cm−2 with a high open circuit voltage of 0.6 V which indicates that Pt@Fe3O4/MWCNT/PANI hybrid nanocomposite is an outstanding electrocatalyst with a great potential for carrying out various electrochemical processes like energy conversion in biofuel cells.

Development of Flexible, Conductive and Biocompatible Chitosan-Based Miniaturized Bioelectrodes for Enzymatic Glucose Biofuel Cells

The need for new clean energy sources for portable devices in biomedical, agro-food industry and environmental related sectors boosts scientists towards the development of new strategies for energy harvesting for their application in biodevices development. In this sense, enzymatic biofuel cells (BFCs) have gained much attention in the last years. This work faces the challenge of develop new generation of BFCs able to be adapted to remote and personal monitoring devices within the framework of wearable technologies. To this aim, one of the main challenges consists of the development of conductive and biocompatible electrodes, which constitute a challenge itself due to the non-conductive capabilities of most of the biocompatible supports. Additionally, bioelectrodes may achieve good mechanical properties and resilience in order to be suitable for the envisioned application, which involves exposure to deformation during long-term use. Furthermore, it is desirable that the systems developed are versatile enough to be adapted to miniaturized supports for new personal wearable devices development. In the present work, self-standing chitosan-carbon black membranes have been synthesized and modified with suitable enzymes for the assembly of an enzymatic glucose BFC. The membranes have been adapted to be integrated in miniaturized interdigitated gold electrodes as the step forward to miniaturized systems, modified with enzymes and metallic particles clusters and tested for energy harvesting from glucose solutions. The miniaturized system produces a power density of 0.64 µW/cm2 that is enhanced to 2.75 µW/cm2 in the presence of the metallic clusters, which constitute a 76% incensement. Such preliminary demonstrations highlight the good response of metals in bioelectrode configuration. However, energy harvesting real application of the developed miniaturized electrodes need still improvements but pave the way for the use of BFC as an energy source in wearable technologies due to their good mechanical, electrical and biocompatible properties.

Flexible and Conductive Bioelectrodes Based on Chitosan-Carbon Black Membranes: Towards the Development of Wearable Bioelectrodes.

Wearable sensors for non-invasive monitoring constitute a growing technology in many industrial fields, such as clinical or sport monitoring. However, one of the main challenges in wearable sensing is the development of bioelectrodes via the use of flexible and stretchable materials capable of maintaining conductive and biocompatible properties simultaneously. In this study, chitosan-carbon black (CH-CB) membranes have been synthesized using a straightforward and versatile strategy and characterized in terms of their composition and their electrical and mechanical properties. In this sense, CH-CB membranes showed good conductivity and mechanical resistance thanks to the presence of carbon black, which decreases the insulating behavior of chitosan, while flexibility and biocompatibility are maintained due to the dual composition of the membrane. Thus, flexible and biocompatible conductive bioelectrodes have been developed by the combined use of CH and CB without the use of toxic reagents, extra energy input, or long reaction times. The membranes were modified using the enzymes Glucose Oxidase and Laccase in order to develop flexible and biocompatible bioelectrodes for enzymatic glucose biofuel cells (BFCs) and glucose detection. A BFC assembled using the flexible bioelectrodes developed was able to deliver 15 µW cm−2, using just 1 mM glucose as biofuel, and up to 21.3 µW·cm−2 with higher glucose concentration. Additionally, the suitability of the CH-CB membranes to be used as a glucose sensor in a linear range from 100 to 600 µM with a limit of detection (LOD) of 76 µM has been proven. Such demonstrations for energy harvesting and sensing capabilities of the developed membrane pave the way for their use in wearable sensing and energy harvesting technologies in the clinical field due to their good mechanical, electrical, and biocompatible properties.

Maximizing the enzyme immobilization of enzymatic glucose biofuel cells through hierarchically structured reduced graphene oxide

The number of immobilized glucose oxidase (GOx) molecules is considerably increased by the structural modification of reduced graphene oxide (rGO), and the performance of enzymatic biofuel cells (EBFCs) is positively affected by the modification process. To do this, new rGO with three-dimensional open porous structure is formed by spray freeze drying method (sprGO), while tetrathiafulvalene (TTF) as mediator, and GOx are sequentially immobilized onto sprGO. To improve the loading amount of catalyst, rGO structure is modified to open porous sprGO structure possessing numerous anchoring sites, after which gelatin film crosslinked by glutaraldehyde is fabricated onto sprGO to prevent any losses of other components (sprGO/[TTF-GOx]/crosslinked-gelatin). Specific surface area and charge transfer resistance of sprGO are quantitatively measured, and the actual amount of immobilized GOx and the performance of EBFC using this catalyst are electrochemically examined. With this, it is found that the amount of GOx immobilized in sprGO/[TTF-GOx]/crosslinked-gelatin is twice better that in rGO/[TTF-GOx]/crosslinked-gelatin. More specifically, EBFC using this catalyst shows open circuit voltage of 0.85 V and maximum power density of 380 μW/cm2, and this is 1.4 times better than that using rGO/[TTF-GOx]/crosslinked-gelatin. These results indicate that the amount of immobilized GOx strongly affects the performance capabilities of EBFCs.

Portable Thermal Management Platform for Synthesis of ZnO Nanoparticle in a Microfluidic Device: Validated for Electrochemical Sensing and Glucose Fuel Cell Applications

Nanoparticles have become omnipresent as they have distinctively diverse properties from their bulk counterparts. They find a considerable research interest in numerous biological, biomedical, biopharmaceutical, and biochemical applications. The productivity and structure of nanoparticles are deeply reliant on the method used for their synthesis. The classical hydrothermal method needs massive and expensive temperature controller instruments, a huge amount of reagents, and specific autoclaves for their synthesis. With this motivation, herein, an automated, integrated, and miniaturized thermal monitoring system has been designed and developed for producing nanoparticle-on-chip (NoC) in a microfluidic platform. Herein, Zinc oxide (ZnO) nanoparticles were synthesized. The device comprises a microcontroller, self-designed switching circuit, cartridge heater, and thermocouple. The device, with dimensions 78 ×75 ×40 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , has benefits such as portability, easy-to-use, amenability to geotagged data logging, and inexpensive. The device showcased the temperature sensitivity of ± 0.5 °C. A polymethyl methacrylate (PMMA)-based microfluidic device, with a suitable microreactor, was fabricated using the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser ablation technique. ZnO nanoparticles were successfully synthesized at 95 °C within 60 min and were subjected to several characterization techniques to manifest their crystographic, elemental, morphologic, and spectroscopic properties. As a proof-of-principle, the produced ZnO nanoparticles were validated for electrocatalytic sensing of hydrazine and uric acid, and as a catalyst in an enzymatic glucose biofuel cell (EBFC) to test its efficiency. The proposed microfluidic thermal system can be utilized for carrying out numerous temperature-based reactions and analyses

Droplet-based lab-on-chip platform integrated with laser ablated graphene heaters to synthesize gold nanoparticles for electrochemical sensing and fuel cell applications

Controlled, stable and uniform temperature environment with quick response are crucial needs for many lab-on-chip (LOC) applications requiring thermal management. Laser Induced Graphene (LIG) heater is one such mechanism capable of maintaining a wide range of steady state temperature. LIG heaters are thin, flexible, and inexpensive and can be fabricated easily in different geometric configurations. In this perspective, herein, the electro-thermal performance of the LIG heater has been examined for different laser power values and scanning speeds. The experimented laser ablated patterns exhibited varying electrical conductivity corresponding to different combinations of power and speed of the laser. The conductivity of the pattern can be tailored by tuning the parameters which exhibit, a wide range of temperatures making them suitable for diverse lab-on-chip applications. A maximum temperature of 589 °C was observed for a combination of 15% laser power and 5.5% scanning speed. A LOC platform was realized by integrating the developed LIG heaters with a droplet-based microfluidic device. The performance of this LOC platform was analyzed for effective use of LIG heaters to synthesize Gold nanoparticles (GNP). Finally, the functionality of the synthesized GNPs was validated by utilizing them as catalyst in enzymatic glucose biofuel cell and in electrochemical applications.

Completely Additive Manufactured and Reusable Microfluidic Device As Enzymatic Glucose Biofuel Cell

Energy devices using electrochemical reactions are emerging as essential power sources, paving the way towards renewable and sustainable energy harvesting. Among various electrochemical energy devices (ECD), enzymatic biofuel cells (EBFC) are gaining more attention due to the production of green energy using biocatalysts such as enzymes and physiological fluids as fuel. These devices are of prime importance because of their unique features, such as high energy density, long-life, portability, and cost-effectiveness. However, they still have some drawbacks including precise and customized designing of devices at the microscale dimensions. This can be overcome by additive manufacturing techniques such as fused deposition modeling (FDM) driven 3D printing to produce accurate micro-devices using conductive filaments with tailored design. In this work, the development of a completely additively manufactured (AM) microfluidic device for the application of enzymatic biofuel cells has been described. The micro-device was 3D printed with ABS filament, whereas the electrodes using conductive graphene/polylactic acid filament using a desktop 3D printer. The design of the electrodes (Figure 1a) (35 mm × 1.5 mm × 1 mm) and microchannel were carried out using Autodesk Fusion 360 software with the required dimensions. Surface modification of the electrode was accomplished using dimethylformamide (DMF) for an optimized time of 10 mins (Figure 1b) and left to air dry overnight. The anodic (glucose oxidase) and cathodic (laccase) enzymes were immobilized on the bioelectrodes by the EDC-NHS coupling mechanism (Figure 1c and 1d). The substrate (glucose) concentration and DMF treatment time were optimized by various trials using electrochemical techniques. The microfluidic device was designed in a way that the device can be reused by inserting bioelectrodes into the respective compartments. The anolyte and catholyte consisted of mediators for enhancing the electron transfer rate during electrolysis. Co-laminar flow was maintained in the device to make it membraneless. This was done by varying the device design parameters and flow rates of the electrolyte with the help of a peristaltic pump. The sequential steps of integration of the bioelectrodes into the microchannel is shown in Figure 1e. Polarization performance of the fabricated bioelectrodes incorporated in the AM microfluidic EBFC was recorded using Chronoamperometry technique at the room temperature. The device was capable of generating a benchmarked power density of 7.95 µW/cm2 with an open circuit voltage of 312 mV. This method of device fabrication for EBFC will help in development of highly efficient ECD by different conductive electrode materials for increasing the efficacy of the micro-device. Figure 1

Graphite electrodes as bioanodes for enzymatic glucose biofuel cell

This study investigates the performance of pencil graphite (PG) electrodes to identify the grade of pencil most suitable as bioanode for enzymatic glucose biofuel cell. Pencils of H, 3H, 5H and B grades are selected for this study. The surfaces of different grade PGs are modified with carboxylic acid functionalized multi walled carbon nanotubes (COOH-MW­CNT/PG), followed by immobilization with glucose oxidase (GOx) to fabricate the respect­tive bioanodes (GOx/COOH-MWCNT/PG). Morphological and electrochemical characteri­zations are carried out using scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry and energy dispersive X-ray spectroscopy. All tested PG electrodes exhibited positive results with variable response characteristics towards glucose oxidation reaction. B-grade PG bioanode is found to have the highest coverage of the deposited nanobiocomposite with the fastest electron transfer rate. The half-cell electrode assembly with this grade of PG recorded the highest current density of 4.25 mA cm-2 at physiological glucose conditions (5 mM glucose, pH 7.0). Enzymatic glucose biofuel cell assembled with B-grade PG bioanode and platinum cathode generated an open circuit potential of 149 mV and maximum power density of 0.789 µW cm−2 from 5 mM glucose at ambient conditions (25 ± 3◦C). The results obtained for B-grade PG bioanode are comparable to those of conventional carbon and glassy carbon electrodes, thus demonstrating its applicability to enzymatic glucose biofuel cells.

Optimization of Method and Components of Enzymatic Fuel Cells

Enzymatic fuel cells produce electrical power by oxidation of renewable energy sources. An enzymatic glucose biofuel cell uses glucose as fuel and enzymes as biocatalyst, to convert biochemical energy into electrical energy. The applications which need low electrical voltages and low currents have much of the interest in developing enzymatic fuel cells. The cell was constructed using three different materials with different electrodes (Bitter leaf and Copper electrodes (BCu), Bitter leaf and Carbon electrodes (BC) and Water leaf and Carbon electrodes (WC)). The short circuit current and open circuit voltage were measured in micro-ampere (mu A) and milli-volt (mV) respectively at 30 minutes interval over the period of 12 hours (from dawn to dusk). The results which show that fuel cells constructed using bitter leaf with carbon electrode has the highest open circuit voltage, short circuit current and generated power of 162.8~mV, 1.65~ mu A and 268.62~nW respectively at 720~mins is obtained from the plots generated by the use of Microsoft Excel. The results show that all short circuit currents, voltages and powers generated increases with time and this is as a result of the exposure to solar radiation during the period of taking the measurement.

Operation stability of chitosan and nafion-chitosan coatings on bioelectrodes in enzymatic glucose biofuel cells.

The performance of bioelectrodes in enzymatic glucose biofuel cell is not only dependent on the enzyme immobilization schemes but it is greatly influenced by the ability of the enzyme to exhibit favorable orientation for a direct electron transfer (DET) between the enzyme and the current collector. The electrochemical investigation of chitosan and nafion-chitosan coatings on multi-walled carbon nanotubes (MWCNTs) immobilized with pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ-GDH) and bilirubin oxidase (BOD) at the bioanode and biocathode, respectively revealed interesting operational stability performance for the enzymatic biofuel cells. The bioelectrodes operated in DET mode and the chitosan coated biofuel cell system overall demonstrated higher power (156 μW) output. The stability of PQQ-GDH bioanodes varied based on the enzyme concentrations, wherein a concentration of 2.5 mg/ml resulted in a significant enhancement in stability and the maximum power density of 1.6 mW/cm2 compared to enzyme concentrations of 5 mg/ml PQQ-GDH or higher.

A “Press and Go” Thin Biofuel Cell Patch for Power Generation

Biofuel cells are devices that generate portable electrical power, typically from glucose, alcohols or related biofuels, by using enzymatic anodes and cathodes. We report on the performance of membrane- and mediator-free enzymatic glucose biofuel cells (BFCs) fabricated in a sandwiched, patch geometry with carbon nanotube nanopaper bio-electrodes prepared using a compression technique to immobilize the enzymes. A gel electrolyte comprised of agar mixed with glucose is sandwiched between the two bio-electrodes to form a patch. Power densities up to 111.90 μW/cm2 at a current density of 334.50 μA/cm2 at a voltage of 0.335 V were obtained for a typical single cell BFC of this design. The sandwich BFC also showed good stability with a half-life of about 1.5 days under continuous operation. The relatively high power density for this new design is attributed to the compression-induced immobilization of the enzymes by the nanotubes as indicated by scanning electron microscope images. This compression-induced immobilization of enzymes provides improved direct electron transfer at the carbon nanotube electrodes.

Towards eco-friendly power sources: In series connected glucose biofuel cells power a disposable ovulation test

A disposable ovulation test is operated using a flow stack of 5 in series connected glucose biofuel cells giving an open circuit voltage (OCV) of 3.5 V. Such tests consume at total around 60 μWh of energy and in average 1.7 mW of power during one run of around 12 min which are supplied by a CR1220 3 V lithium button battery in the commercialized device. We replaced this battery by the glucose biofuel cell stack and observed during the measurements and display steps peak currents up to 1.4 mA inducing a voltage drop down to 2.8 V during few seconds (4 mW of power consumption). Even such power peaks are supported by the presented biofuel cell stack assuring the necessary operational cell voltage and current. After the measurements towards Luteinizing Hormone (LH) detection the display remains turned on for 8 min and consumes just 2 μW which allows to reestablish the initial OCV and to run a further test. The presented results demonstrate as proof of concept the suitability of eco-friendly enzymatic glucose biofuel cells as alternative power source for disposable devices.

Dawson-type polyoxometalate nanoclusters confined in a carbon nanotube matrix as efficient redox mediators for enzymatic glucose biofuel cell anodes and glucose biosensors

Two new inorganic-organic hybrid materials based on heteropolyoxometalates (POMs): (C4H10N)6[P2Mo18O62]·4H2O (P2Mo18) and (C6H8NO)4[H2P2W18O62]·6H2O (P2W18) are reported as mediators for electron transfer between FAD-dependent glucose dehydrogenase (FAD-GDH) and a multiwalled carbon nanotube (MWCNT) matrix for glucose biofuel cell and biosensor applications. These polyoxometalates were chosen due to their promising redox behavior in a potential range for mediated electron transfer with the glucose oxidizing enzyme, FAD-GDH. P2Mo18 and P2W18 were immobilized on 1-pyrenemethylamine (PMA) functionalized MWCNT deposits. After immobilization of FAD-GDH, the P2W18-modified MWCNT electrode demonstrated mediated electron transfer and provided a catalytic current density of 0.34 mA cm−2 at 0.2 V vs SCE with an open circuit potential (OCP) of −0.08 V vs SCE. A 10-fold increase in catalytic current to 4.7 mA cm−2 at 0.2 V vs SCE and a slightly lower OCP of −0.10 V vs SCE was observed for an equivalent electrode modified with P2Mo18.The apparent superiority of P2Mo18 is related, at least in part, to its improved incorporation in the MWCNT matrix compared to P2W18. Both POM-modified bioanodes showed exceptional stabilities with 45% of their initial performances remaining after 15 days. The mediated electron transfer capacities of the POMs were also evaluated in a glucose sensor setup and showed very satisfying performances for glucose detection, including a sensitivity of 0.198 mA mol L−1 cm−2, a satisfying linear range between 1 mmol L−1 and 20 mmol L−1, and good reproducibility for the P2Mo18 electrode.

Polyethyleneimine Modified Carbon Cloth Anode for Self-Pumping Enzymatic Glucose Biofuel Cell

This paper proposes a simplified process that immobilizes enzymes onto carbon cloth electrodes to increase biofuel cell functionality. Polyethyleneimine (PEI) is used to modify carbon cloth electrodes to reduce the processing time and increase self-pumping enzymatic glucose biofuel cell (self-pumping EGBC) electricity. PEI is usually used in biochemical engineering gene transfection as GOx support to enhance enzyme immobilization. PEI is a good candidate for increasing enzymatic biofuel cell (EBC) redox current. PEI and GOx have been successfully immobilized onto carbon cloth electrodes through FT-IR analysis. A UV/Vis spectrophotometer was used to investigate the best PEI support concentration. PEI was proven to improve redox current by cyclic voltammetry analysis. The results show that the GOx/PEI electrode has excellent hydrophilicity on the GOx/PEI electrode surface using contact angle measurement. The optical and electrochemical analysis result shows that GOx/PEI was successfully immobilized onto carbon cloth electrodes. Experimental analysis showed that self-pumping EGBC achieved a power output of 0.609 mW/cm2 (126.9 mW/cm3). PEI contributes to the shortening of the process from a few hours to 5–10 minutes and enhances GOx fuel cell performance.

Generating usable electric power while sensing glucose

Herein a system capable of simultaneously sensing glucose and harnessing sufficient energy to power a digital device is presented. This system is powered by an enzymatic glucose biofuel cell consisting of pyroloquinoline quinone glucose dehydrogenase-modified bioanode and bilirubin oxidase-modified biocathode. The electrical parameters from a single biofuel cell were amplified to 1.4 V using a charge pump circuit consisting of a capacitive element that senses glucose. Furthermore, a steady output DC supply of 3.2 V was obtained by interfacing a step-up DC convertor circuit to the charge pump circuit. Such a system simultaneously senses glucose and harnesses energy in the presence of various glucose concentrations. The self-powered glucose biosensor exhibited an improved sensitivity of 86.42 Hz/cm2 mM with a linear range extending to 20 mM when operating a digital device simultaneously. This is a 3.7-fold increase in sensor sensitivity when compared with previous self-powered glucose biosensors. This novel self-powered glucose biosensing system shows a promising future for powering implantable devices and assessing patient health.

A self-powered glucose biosensor based on pyrolloquinoline quinone glucose dehydrogenase and bilirubin oxidase operating under physiological conditions.

A novel biosensing system capable of simultaneously sensing glucose and powering portable electronic devices such as a digital glucometer is described. The biosensing system consists of enzymatic glucose biofuel cell bioelectrodes functionalized with pyrolloquinoline quinone glucose dehydrogenase (PQQ-GDH) and bilirubin oxidase (BOD) at the bioanode and biocathode, respectively. A dual-stage power amplification circuit is integrated with the single biofuel cell to amplify the electrical power generated. In addition, a capacitor circuit was incorporated to serve as the transducer for sensing glucose. The open circuit voltage of the optimized biofuel cell reached 0.55 V, and the maximum power density achieved was 0.23 mW/ cm2 at 0.29 V. The biofuel cell exhibited a sensitivity of 0.312 mW/mM.cm2 with a linear dynamic range of 3 mM - 20 mM glucose. The overall self-powered glucose biosensor is capable of selectively screening against common interfering species, such as ascorbate and urate and exhibited an operational stability of over 53 days, while maintaining 90 % of its activity. These results demonstrate the system's potential to replace the current glucose monitoring devices that rely on external power supply, such as a battery.

Study of Electrode Structures and Redox Kinetics in Biofuel Cells

Selection of the anode-cathode electrodes materials and structure is one of the critical challenges of bio fuel cell application. They can affect the power density and columbic efficiency. Two types of bio fuel cell were studied, the Microbial Fuel Cell (MFC) and the Enzymatic Fuel Cell (EFC), where the electrode structure and kinetics are similar except for the rates of redox reaction. The electrochemical characteristics of the In the MFC the anode was inoculated with MRS broth containing Lactobacillus Cesai Shirota. Complete characterisation and optimisation of the redox kinetics will be presented. Mediators will be used to enhance electron transfer between the fuel, bacteria and electrodes to improve electrode kinetics. A fast and convenient bacterial immobilization method will be proposed as an attempt to improve the anode efficiency of a microbial fuel cell, in which bacteria will be entrapped. The electron transfer characteristics with the mediators and immobilizers shall be studied by cyclic voltammetry and SEM imaging. Enzymatic Fuel Cell is a specific type of bio fuel cell that uses enzymes as a catalyst to oxidize its fuel, instead of precious metals. Enzymatic glucose biofuel cells convert chemical energy stored in glucose into electricity. Enzymatic oxidation from complex sugar is carried out by glucose selective enzymes such as glucose oxidase (Gox) and oxygen reducing enzyme namely laccase. These reactions are highly enzyme specific and occur at relatively mild conditions (Neutral pH and ambient temperature). The specific materials and structure for the electrodes used in enzymatic fuel cell can affect the power density and columbic efficiency. This glucose EFC cell features a 3-D porous carbon anode and cathode, for high surface area for the reaction, a suitable immobilizer for the enzyme immobilization and mediators like ferrocene for optimal electron transfer. The achievable cell potential is between 0.7- 0.8V. The achieved power density is still below theoretical value. The EFC will be optimized for enzyme loading; conductive loss minimization, both electronic and ionic, direct charge transfer for improving charge transfer efficiency, and pore channel and size profile.

Novel Materials-Based Stretchable and Self-Healing Electrochemical Sensors for Wearable Applications

Printed electronics has acquired tremendous attention recently and its market size is expected to reach $300 billion over the next two decades. Printed electrochemical sensors, in particular, are an important sub-section of printed electronics that play a pivotal role in healthcare, energy and security domains. However, the fragile nature of these printed electrochemical devices greatly hampers the complete harnessing of their potential in many scenarios, such as, wearable applications, where harsh mechanical deformations are fairly common. External stress induced device failure is indeed the “Achilles heel” of the printed electronics field and yet not much has been done to develop printed devices that can withstand extreme stress and self-heal upon damage. We have thus attempted to fill this scientific vacuum by fabricating the first examples of all-printed, inexpensive, highly stretchable and self-healing electrochemical sensors. These novel devices have been realized by judiciously synthesizing screen printable inks that contain elastomeric binders and microcapsules loaded with self-healing agent. PEDOT:PSS[1] and CNT[2] based stretchable inks have been developed for fabricating stretchable electrochemical sensors that can withstand extremely high levels of strains (upto 500%) with negligible effect on their structural integrity and performance. The sensors have been extensively characterized by electrochemical techniques to study the effect of repeated stretching (500%), torsional twisting (1800) and indenting (5mm) on their electrochemical properties. Finally, the wide-range applicability of this platform to realize highly stretchable electrochemical sensors and biofuel cells has been demonstrated by fabricating and characterizing potentiometric ammonium ion sensor, amperometric glucose sensor and enzymatic glucose biofuel cell and self-powered sensor. The self-healing printed electrochemical sensors rely on the release of healing agent from microcapsules that loaded within the inks.[3] Upon damage, the microcapsules release the healing agent that leads to local dissolution of the binder and allows redistribution of the conductive fillers to regain the sensor’s electrochemical properties. Thorough characterization of the self-healing sensors reveal that their electrochemical properties can be restored within a few seconds even when the device is completely damaged. Ultimately, we utilized this platform to demonstrate a self-healing sodium sensor that can self-restore its sensing ability even after complete damage. The stretchable and self-healing printed electrochemical sensors have immense applications in the field of wearable electrochemical sensors.[4] These devices can be easily mated with the human skin for continuous non-invasive monitoring of vital chemicals, such as, electrolytes (Na+, NH4 +, Cl-etc) and metabolites (lactate, sodium, alcohol etc). The stretchable and self-healing ability of these devices enable them to endure extreme deformations commonly experienced by the human skin and yet perform without much impact of their sensing ability. Our work thus holds great promise in the wearable healthcare domain wherein defiance towards extreme mechanical deformations is crucial.