Shaegh et al.[37] worked on air-breathing microfluidic fuel cells with fuel reservoirs (Fig. 12) and found that the ohmic losses are mini-mal because of the low anode-to-cathode spacing and improved mass transport. These changes were the result of a supply of a uniform fuel concentration over the anode and efficient bubble removal from the anode active sites. Erik et al.[75] measured the microfluidic diffusion in H-cells, and their work proved that the H-cell design allows for a fast, efficient and cheap method to analyse diffusion.