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 Ω used to heat the reaction mix, while the top layer has a resistance of 1.1 Ω to heat the vial body, preventing vapor condensation. The top board was maintained at ~ 110 ± 1 °C during all cycles. The final device was able to heat and cool down the reaction at rates of ~ 2.0 °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.

本文介绍了一种用于检测疾病的低成本聚合酶链反应 (PCR) 仪器的制造。为了降低仪器价格并简化结构，我们开发了一种替代制造工艺，将传统的印刷电路板 (PCB) 转变为加热元件，避免使用铝制加热/冷却块和 Peltier 设备。为了冷却反应，使用了一个简单的电脑风扇。小瓶支架使用两个双面 PCB 板组装成三明治状配置。底部 PCB 的电阻为 0.9 Ω，用于加热反应混合物，而顶层的电阻为 1.1 Ω，用于加热瓶身，防止蒸汽冷凝。在所有循环期间，顶板保持在 ~ 110 ± 1 °C。最终设备能够以 ~ 2 的速率加热和冷却反应。0 °C/s，与商业热循环仪相当的速率。SMD NTC 热敏电阻用作温度传感器，并实施 PID（比例-积分-微分）控制算法来获取和精确控制温度。我们还讨论了仪器是如何校准的。该设备已成功测试用于放大梅毒螺旋体细菌 DNA 和寨卡病毒 RNA 样本，表现出与商业 PCR 仪器相似的性能。