Integrating micro metal-air batteries in lateral flow test for point-of-care applications

Lateral flow test assay requires integrated micro power sourcesto realize quantitative testing as well as to enhance accuracy. Conventional dry batteries generally havepollution issues for this task, while the recently emerged paper-based fuel cells are both expensive and low-voltage that restrict their usage. In comparison, the metal-air battery (MAB) using a metal anode and an air-breathing cathode could be a much better solution. In this study, different micro metal-air batteries are integrated onto paper substrates, producing micro power sources that are low-cost, high-voltage and environmentally friendly. Their performances are compared under both alkaline and salt electrolytes in terms of power output, fabrication cost and specific energy. Among them, the Al-air battery with an alkaline electrolyte and the Mg-air battery with a salt electrolyte are more advantageous than others, achieving high voltage outputs of 1.55 V and 1.53 V at 1 mA cm⁻², respectively. By using acarbon grid instead of asilver grid as current collector, and nitrogen-doped carbon nanotubesinstead of MnO₂ as oxygen reduction catalyst, the as-fabricated micro MABs can be much cheaper and greener for disposable lateral flow test devices. Finally, a two-cell micro Al-air battery pack, which is integrated into a digital pregnancy tester, provides powersuccessfully for its operation for more than 5 minutes.