Lactate/O-2 biofuel cells (BFC) can have high theoretical energy densities due to high solubility and high fuel energy density; however, they are rarely studied in comparison to glucose BFCs. In this paper, lactate oxidase (LOx) was coupled with a ferrocene-based redox polymer (dimethylferrocene-modified linear polyethylenimine, FcMe(2)-LPEI) as the bioanode and laccase (Lc) connected to pyrene-anthracene modified carbon nanotubes (PyrAn-MWCNT) to facilitate the direct electron transfer (DET) at the bio-cathode. Both electrodes were evaluated in two BFC configurations using different concentrations of lactate, in the range found in sweat (0-40 mM). A single compartment BFC evaluated at pH 5.6 provided an open circuit potential (OCP) of 0.68 V with a power density of 61.2 mu Wcm(-2). On the other hand, a microfluidic BFC operating under the same conditions resulted in an OCP of 0.67 V, although an increase in the power density, increasing to 305 mu W cm(-2), was observed. Upon changing the pH to 7.4 in only the anolyte, its performance was further increased to 0.73 V and 404 mu W cm(-2), respectively. This work reports the first microfluidic lactate/oxygen enzymatic BFC and shows the importance of microfluidic flow in high performing BFCs where lactate is utilized as the fuel and O-2 is the final electron acceptor. (C) 2016 Elsevier B.V. All rights reserved.