A low-cost PCR instrument for molecular disease diagnostics based on customized printed circuit board heaters

This article describes the fabrication of a low-cost Polymerase Chain Reaction (PCR) instrument to detect diseases. In order to reduce the instrument price and simplify construction we developed an alternative fabrication process, transforming conventional printed circuit boards (PCB) in heating elements, avoiding the use of aluminum heating/cooling blocks and Peltier devices. To cool down the reaction a simple computer fan was used. The vial holder was fabricated using two double side PCB boards assembled in a sandwich-like configuration. The bottom PCB has a resistance of 0.9 Omega used to heat the reaction mix, while the top layer has a resistance of 1.1 Omega to heat the vial body, preventing vapor condensation. The top board was maintained at similar to 110 +/- 1 degrees C during all cycles. The final device was able to heat and cool down the reaction at rates of similar to 2.0 degrees C/s, a rate comparable to commercial thermocyclers. An SMD NTC thermistor was used as temperature sensors, and a PID (proportional-integral-derivative) control algorithm was implemented to acquire and precisely control the temperature. We also discuss how the instrument is calibrated. The device was tested successfully for the amplification of T. pallidum (Syphilis) bacterial DNA and Zika virus RNA samples, showing similar performance to a commercial PCR instrument.

Automated summary

This article describes the fabrication of a low-cost PCR instrument with alternative processes, utilizing PCB heating elements, a computer fan for cooling, and PID control algorithm for temperature control. The device successfully amplified samples of T. pallidum and Zika virus RNA, showing similar performance to commercial PCR instruments.