Increasing energy-efficiency of microheating in handheld nucleic acid amplification tests

Pocket-sized isothermal nucleic acid amplification tests (NAATs) have shown significant promise during the recent SARS-CoV-2 pandemic to decentralize diagnostics and increase the speed of detection. However, a key technical challenge is solving heating in an energy-efficient, robust and scalable manner. This work presents a novel top-down heating approach using PCB trace heaters and metal heat spreaders integrated into the microreactors, optimized through experimental and simulated thermal analysis. In simulations, the effect of vertical geometry and material composition were evaluated, as well as the effect of heat spreader geometry. Experimental thermal transient analysis focused on evaluating operational performance at ambient temperature limits expected in home, office and clinical use. The design achieved reliable operation at ambient temperatures of 15-30°C with a steady-state error <1°C and average power consumption of 1W and could be powered from any USB3.0+ compliant port.