Development of a portable PCR Thermal Cycler with improved dynamic response and thermal stability

Polymerase Chain Reaction (PCR) requires precise and repeatable thermal cycling to amplify DNA without sample degradation, particularly for microliter-level volumes. This paper presents the design and development of a compact and efficient thermal cycler capable of meeting the crucial temperature requirements of PCR using a PID profiler-based control strategy. The system incorporates a custom fabricated copper sample holder accommodating four conical PCR microtubes. These tubes are having a usable sample volume of 8–10 µL each, optimized for rapid thermal response and uniform heat distribution. A TEC1-12706 Peltier module enables rapid heating and cooling, supported by a heat sink for effective thermal dissipation. Sample temperature is monitored using a miniature K-type thermocouple, calibrated up to 110 °C with an accuracy of ±0.3 °C and a response time of about 2.8 s. A mathematical model of the thermal system, and the Peltier module heat equation, was developed to validate controller performance. A programmable PID profiler is implemented to automatically track the multi-stage PCR temperature profile. Controller parameters were tuned using Ziegler Nichols method, yielding optimized constants Kp = 2.8, Ti = 30 s, and Td = 0.05 min. The system achieved the ramp rate of 8.6 °C/s with minimal overshoot (≤0.4 %), steady-state accuracy within ±0.2 °C, and stable performance. The response demonstrates settling times of 28 s for heating and 18 s for cooling. The developed thermal cycler is portable, cost-effective, and capable of accurately following the PCR temperature profile, confirming its suitability for DNA amplification applications.