Performance Analysis And Vibration Resistance Study Of Microfluidic Microbial Fuel Cell

Microbial fuel cell(MFC)is a green energy technology which utilizes the bacterial biocatalysis to directly convert chemical energy of organic matter into electrical energy.Thanks to the development of micromachining technology,Microfluidic microbial fuel cell(MMFC)has attracted extensive attention in recent years due to its high energy density and low cost.Furthermore,MMFC is considered to have potential for industrial applications such as new portable energy,implantable biomedical devices and miniature biosensors.At present,the research on MMFC is still in experimental stage due to the low power generation of MMFC.In order to accelerate the industrial application of MMFC,it is crucial to deeply understand the fluid flow,mass transfer mechanism and microbial growth inside the cell at micro scale.In addition,it is necessary to consider the possible interference of external factors in the actual operation of MMFC.To address the shortage of theoretical studies on MMFC,this paper constructs numerical models of MMFCs with different structures and analyzes the cell performance response under the influence of different parameters.The main research contents of this paper are as follows:(1)A numerical model of the MMFC with two-dimensional planar electrodes is constructed,and the effects of temperature,concentration,ionic strength and flow rate on the overall performance of the cell are analyzed;(2)A MMFC model with three-dimensional porous electrodes is constructed to investigate the fluctuation of cell performance under different p H values and electrode porosities.In addition,the proposed model reveals the inhomogeneous distribution of dual-population microorganisms inside the electrodes.(3)Fluid behavior and microbial growth in the MMFC under vibration excitation is simulated.The proposed model predicts the effects of vibration on the overall performance of the MMFC,and further evaluates the anti-vibration performance of the MMFC at different flow rates.The main research achievements of this paper are as follows:(1)Too low or too high temperatures can reduce the bioactivity of electricigens,which can lead to a decrease in the cell electricity-producing performance.Lowering the flow rate is detrimental to the cell electricity-producing performance,but it will increase the fuel utilization.Therefore,at high substrate concentrations,an appropriate reduction in flow rate can be chosen to increase cell economy,but attention should be paid to avoid the penetration of toxic catholyte into the anode biofilm.(2)In the absence of buffers,the bioelectrochemical reactions of MMFC possessing three-dimensional electrodes lead to the accumulation of H~+and OH~-at the two electrodes,which creates a p H gradient inside the cell and inhibits microbial growth.In addition,for MMFCs with air-breathing cathodes,p H mainly affects the anode performance.(3)High electrode porosity is conducive to the diffusive penetration of substrate and oxygen,which promotes the increase of the bacterial content at two electrodes,and also provides a competitive advantage for the growth of aerotolerant anaerobes at the cathode.However,the high porosity leads to a reduction in the effective conductivity of the electrode.Therefore,the MMFC achieves the best output performance when the electrode porosity is 0.6.(4)Excessive vibration force will destroy the laminar flow form of the fluid in the microchannel,resulting in solution mixing,and seriously weaken the MMFC performance.In addition,part of the substrate is transferred from the anode to the cathode through the vibration effect.Therefore,the growth of anaerobic electricigens inside the anode is inhibited under vibrational conditions,while the content of bacteria inside the cathode increases.(5)The residence time of the substrate inside the cell microchannel is shorter at high flow rates,which mitigates the negative effects of vibration force.As a result,MMFC has better anti-vibration performance at high flow rates,but the increased flow rate reduces the cell substrate removal rate.Appropriate vibration conditions can improve the cell substrate removal rate.