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 la) (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/cm~2 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.
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