PT - JOURNAL ARTICLE AU - John P. Goertz AU - Kenya M. Colvin AU - Andrew B. Lippe AU - John L. Daristotle AU - Peter Kofinas AU - Ian M. White TI - Multi-stage chemical heating for instrument-free biosensing AID - 10.1101/367029 DP - 2018 Jan 01 TA - bioRxiv PG - 367029 4099 - http://biorxiv.org/content/early/2018/07/11/367029.short 4100 - http://biorxiv.org/content/early/2018/07/11/367029.full AB - Improving the portability of diagnostic medicine is crucial to 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 multi-step diagnostic assays using chemically generated, passively regulated heat. Ligation and polymerization reagents for Rolling Circle Amplification of nucleic acids are separated by melt-able 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 while fatty acids embedded in a carbonaceous matrix passively buffer the temperature around their melting points. Achieving multi-stage temperature profiles extends the capability of instrument-free diagnostic devices and improves the portability of reaction automation systems built around phase-change partitions.