Microfluidic fuel cells on paper: meeting the power needs of next generation lateral flow devices†
Lateral flow test strips have dominated the rapid diagnostics landscape for decades. Recently, the emergence of paper microfluidics has brought new functionalities to these porous materials, and the search for instrument-free point-of-care devices has driven the development of different types of energy sources to fulfill their power needs. This work presents the development of microfluidic fuel cells as paper-based power sources in a standard lateral flow test format. These fuel cells benefit from the laminar flow occurring in a porous material by capillarity to separately react with two parallel streams, anolyte and catholyte, without an ionic exchange membrane or external pumps. It has been shown that the devices are capable of delivering power densities in the range of 1–5 mW cm−2 using solutions of methanol and KOH. The incorporation of a conjugate pad to store the KOH electrolyte in a solid form and a methanol-rich agar gel on top of the reaction membrane allows the fuel cell to function soaking a single sample pad with just water. The presented microfluidic fuel cell approach would enable a more straightforward integration with typical lateral flow test strips and a cost-effective manufacturing. This work represents the starting point in the development of a power source for capillary-based autonomous sensing systems capable of harvesting the energy needed for the measurement from the biological sample to be analyzed.