In the NINA heater for LAMP, we used the exothermic reaction of calcium oxide (CaO, or quicklime; Science Stuff, Inc., Austin, TX, USA, Cat # C1450) and water to generate the necessary heat. To keep the isothermal device within the temperature band required for LAMP, the reaction chambers were surrounded with an engineered fat-based compound with a high specific heat capacity and specific melting range centered around 65uC (Renewable Alternatives, Inc., Columbia, MO, USA). While several prototype heater designs have been explored, the optimized heater uses an off-the-shelf insulated food storage container (a ''thermos'') to provide an insulated housing with two chambers ( Figure 5 ). The bottom chamber contains the exothermic reaction, and the upper chamber contains the EPCM and reaction wells. To facilitate directed heat transfer to the reaction wells, an aluminum ''honeycomb'' material (Plascore, Inc., Zeeland, MI, USA) was added to the upper chamber prior to introduction of the EPCM. The machined reaction wells, sized to closely fit a standard 200-mL PCR tube, are embedded in the EPCM. Three reaction wells were used for most prototypes (one for a positive control, one for a negative control, and one for an unknown specimen); however, the existing prototype could easily be modified to accept several times this number without significant loss of performance, based on the available space in the EPCM and first principles of heat transfer. An inexpensive spring timer (manufacturer's suggested retail price [MSRP] <10 US$) with an audible ''ready'' indicator was affixed to the lid of the heater unit for added electricity-free functionality.