A membraneless microfluidic fuel cell with continuous multistream flow through cotton threads

In typical membraneless microfluidic fuel cells, the anolyte and catholyte are driven by syringe pumps, increasing the overall size of the system and limiting its miniaturization. In this study, a membraneless microfluidic fuel cell with continuous multistream flow through cotton threads was proposed. Cotton threads are simply laid in parallel to form flow channels. Multistream flow through cotton threads is formed without any external pumps. Cell performances under various operation conditions are evaluated. The results show that the middle stream could separate other two streams effectively to prevent the diffusive mixing of anolyte and catholyte. A peak power density of 19.9 mW cm−2 and a limiting current density of 111.2 mA cm−2 are delivered. Moreover, the performance improves with the sodium formate concentration rising up to 2M, while it declines at 4M fuel concentration due to the weakened convection transport and product removal caused by the low flow rate. With increasing the flow rate, the performance is enhanced because of the improved fuel transport at the anode. The good performance as well as the constant-voltage discharging curve indicates that the microfluidic fuel cell with cotton threads as flow channels provides a new direction for miniature power sources.