In the current case, improvements to the Arrhenius method for study of EABs are realized by applying lab-on-a-chip approaches to analytical chemistry for improved measurement precision and experimental control. Microfluidics is the science and technology of liquid manipulation at the sub-millimeter scale at which hydrodynamic and thermal behaviours can be exploited for precision studies. These advantages have been combined with on-chip characterization and applied to studies of bacterial biofilms as a new class of bioanalytical platforms that continue to gain acceptance. When applied to Arrhenius studies of EABs, the high thermal conductivity at small length scales on-chip can be exploited to accurately set experimental temperatures, which has provided control and experimental flexibility for life-science studies. Properly exploiting this property requires a local heat source and temperature sensing. Moreover, the rapid development of on-chip electrochemistry enables improved EAB studies by exploiting these microfluidic advantages. We have previously developed a protocol for 3-electrode microfluidic devices that includes graphite working and counter electrodes for use in hydrodynamic studies on pure-culture biofilms, without any concern for background currents arising from electrode instabilities, such as corrosion. More recently, these devices have included the ability to establish anaerobic conditions for studies of pure-culture G. sulfurreducens EABs. Combined with the advantages of inert graphite electrodes, long-term studies on pure culture G. sulfurreducens have been demonstrated up to nearly one year along with providing stable conditions for accurate studies of reaction kinetics at ambient conditions, switches to metabolic states, and effects of pH. Recently, we have demonstrated that combining the above advantages with a new reactor design that directs liquid vertically against the top of the EAB, can nearly erase any inhomogeneities in the boundary layers which we proposed as a method to study biofilms under highly defined conditions. Taken together, a microfluidic approach with the above features can provide significant improvements over literature studies of the EAB metabolic bottlenecks, which were previously performed on unpoised electrodes in microbial fuel cells and/or on mixedspecies EABs. In this work, we exploit a microfluidic platform that incorporates all the advancements above to obtain measurements of activation energy such that the mechanistic bottlenecks can be identified for early-stage and fully-grown biofilms under accurate manipulations of concentrations and flow rates. In doing so, we have revealed that not only do the reaction bottlenecks fundamentally switch during maturation, but also that experimental conditions can play a role based on changes to acetate permeability into the EAB.