Development of a Heating Block as an Aid for the DNA-Based Biosensing of Plant Pathogens

Deoxyribonucleic acid (DNA)-based biosensors are rapid, cost-effective, and portable devices for monitoring crop pathogens. However, their on-field operations rely on a laboratory-bound heating block, which controls temperature during sample preparation. This study aimed to develop a field-deployable heating block to assist in the DNA hybridization protocol of DNA-based biosensors. It should maintain 95 °C, 55 °C, and 20 °C for 5, 10, and 5 min, respectively. It had aluminum bars, positive thermal coefficient ceramic heaters, a Peltier thermoelectric module, and DS18B20 thermistors, serving twelve 0.2 mL polymerase chain reaction (PCR) tubes. An Arduino microcontroller employing a proportional–integral–derivative (PID) algorithm with a solid-state relay was utilized. Machine performance for distilled water-filled PCR tubes showed a maximum 10 °C thermal variation. The machine maintained (96.00±0.97) °C, (55.15±2.17) °C, and (17.75±0.71) °C with root mean square errors (RMSEs) of 1.40 °C, 2.18 °C, and 2.36 °C, respectively. The average thermal rates were (0.16±0.11) °C/s, (0.29±0.11) °C/s, and (0.14±0.07) °C/s from ambient to 95 °C, 95 °C to 55 °C, and 55 °C to 20 °C, respectively. Overall, the low standard deviations and RMSEs demonstrate thermostable results and robust temperature control.