Stacked Spring-Based Nonelectric Fuel Delivery System for the Operation of Microfluidic Fuel Cells

Research on microfluidic fuel cells (MFCs) primarily focuses on developing novel electrode designs or optimizing channel architectures to enhance electrical power output. For research purposes, a vast majority of MFCs are operated by using electrical syringe pumps. However, for practical applications of MFC as a power source for small and portable electronics, auxiliary systems such as fuel delivery systems need to be developed. To maximize the electricity generated from the fuel cells, the fuel delivery system should require low electricity or ideally no electrical power at all. This study proposes a nonelectric fuel delivery system for MFCs using mechanical energy stored in wound up helical springs, which is released in a controlled manner. These springs, arranged in a stacked configuration, enable sequential operation, extending the pump’s operational duration. The pump, driven by stacked springs, provides a constant flow rate for up to 140 min. Paired with a fuel cell system, it demonstrates nonelectric fuel cell operation, generating electricity. For demonstration, a membraneless microfluidic abiotic glucose–O₂ fuel cell (m-GFC) system is constructed with Au–Pt and Pt nanoparticles deposited on a laser-scribed graphitic carbon (LSG) surface over a polyimide film. Coupled with the nonelectric syringe pump, glucose and saturated O₂ in KOH solutions continuously flow into the m-GFC, generating electrical energy. The m-GFC supplied with KOH solution containing glucose and saturated O₂ exhibits a maximal power output of 0.65 mW/cm², a current density of 1.5 mA/cm², and a cell voltage (E_cell) of 475 mV. The results show that the nonelectric pump serves as an effective fuel delivery system, eliminating the reliance on conventional electrical pumps and enabling practicality and portability of MFCs.