Microfluidic fuel cell with ultrahigh flow rates, a potential technology for combined cooling and power applications

Microfluidic fuel cell (MFC) generally adopts two microfluidic electrolytes for power generation, which can also be integrated with a heating system for microfluidic cooling, leading to a combined cooling and power technology. To achieve this goal, the electrolyte flow rate needs to be significant increased to guarantee strong cooling effect. Conventional MFC researches have long avoided the ultrahigh flow regime due to stability concerns, yet our work demonstrates for the first time that stable co-laminar flow can still be maintained even at a flow rate as high as 100 mL/min (Re = 677.4), effectively harnessing the ultrahigh flow regime for enhanced cooling ability. With a room-temperature electrolyte flowing at 100 mL/min, the heating system subjected to a 5 W/cm² heat load can be cooled from 392 to 82 °C, corresponding to 79 % reduction of its surface temperature. However, the MFC peak power density of 29.2 mW/cm² was not optimal under this ultrahigh flow rate due to the moderate electrode temperature of 46.1 °C originated from the efficient cooling. To mitigate this cooling-power trade-off, the MFC structure was optimized by repositioning its electrodes and current collectors to the higher temperature zone near the channel outlet. This innovation yields 42 % boost in the peak power density, reaching 41.5 mW/cm², while still preserving the same cooling performance. To sum up, this study showcases the great potential of ultrahigh-flow-rate MFCs for combined cooling and power applications. In the future, more efforts will be paid to further improve its power output. © 2025 Elsevier Ltd