Design and Development of a Field-Deployable Water Bath for Loop-Mediated Isothermal Amplification Assay

Nucleic acid testing has become a prominent method for rapid microbial detection. Unlike polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP) is a simple method of nucleic acid amplification where the reaction can be performed at a constant temperature and the output provided in a colorimetric format. A transparent water bath is a desirable instrument to perform the heating and observe the visual results. However, existing methods of heating water are not convenient for loading and unloading the test samples. Here, we developed a field-deployable water bath—an isothermal heater called IsoHeat for short—which is dedicated to performing LAMP reactions. Using 3D-printing and laser-cutting technology, we fabricated different parts and mechanically assembled the parts to develop the device. Users can commence the heating by pressing the start button on the screen after entering the target temperature. Subsequently, the device heats the water and maintains the target temperature through a PID algorithm-based control system. We demonstrate that IsoHeat can operate in environmental temperatures ranging from $5~^{\circ }$ C to $33~^{\circ }$ C, and it can conduct LAMP reactions in liquid format as well as in paper-based devices. IsoHeat is more efficient and user-friendly compared to a commercially available immersion-heating device, which is often used to perform LAMP reactions. This newly developed device would be helpful to detect pathogens conveniently in the field (e.g., at point-of-care for human applications, on farms for plant and animal applications, and in production facilities for food safety applications).