High-performance flexible microfluidic fuel cell based on braided palladium electrodes

•A cotton thread fiber-based braided passive microfluidic fuel cell is proposed.•The electrode spacing, braiding method and number of braided fibers are explored.•The best cell performance is obtained at 10 intermediate flow channel fibers.•The optimal current density is 94.65 mA/cm2 while power density is 34.07 mW/cm2. Passive microfluidic fuel cells based on fiber materials do not require external pumps and proton exchange membranes. With its simple structure and high energy density, it shows a large potential in micro power supply and testing devices. Most studies have focused on the experimental preparation of paper-based and carbon cloth-based fuel cells. However, there is a lack of simulation to investigate the wicking process and mass transfer of complex thread-based microfluidic fuel cells. Therefore, this study proposes a cotton thread-based passive microfluidic fuel cell with a complex three-strand braided structure. Combined with multi-physics fields, the dynamic mass transfer process, electrochemical reaction mechanism and ionic conduction characteristics inside the cell under the wicking effect and gravity are explored, providing a new perspective for understanding the cotton thread-based fuel cell. Adapting the structural parameters has revealed the complex relationship between the structure and the cell performance. Meanwhile, this study achieved optimization by redesigning the electrode spacing, and the cell outputs the best performance (94.65 mA/cm2 and 34.07 mW/cm2) when 10 cotton threads are set in the middle of the cell. The optimization not only improves the overall cell performance but also provides a practical direction for improvement in subsequent fuel cell designs. [Display omitted]