Multistage Chemical Heating for Instrument-Free Biosensing.

Improving the portability of diagnostic medicine is crucial for alleviating global access-to-care deficiencies. This requires not only designing devices that are small and lightweight, but also autonomous and independent of electricity. Here, we present a strategy for conducting automated multistep diagnostic assays using chemically generated, passively regulated heat. Ligation and polymerization reagents for rolling circle amplification of nucleic acids are separated by meltable phase-change partitions, thus replacing precise manual reagent additions with automated partition melting. To actuate these barriers and individually initiate the various steps of the reaction, field ration heaters exothermically generate heat in a thermos, whereas fatty acids embedded in a carbonaceous matrix passively buffer the temperature around their melting points. Achieving multistage temperature profiles extend the capability of instrument-free diagnostic devices and improve the portability of reaction automation systems built around phase-change partitions.