Design and implementation of a nonlinear controller for thermal cycler with application to DNA amplification

Polymerase chain reaction (PCR) is a process in biology to amplify deoxyribonucleic acids (DNAs) up to several billions. The amplified DNAs are mostly used to diagnose, detect and identify different kinds of diseases. In this paper, a theoretical modeling of a PCR thermal cycler is developed. The model includes a custom-made aluminum plate to put the micro-tubes in it, an industrial single-stage thermoelectric module, a thermal pad, a heatsink and a fan. Based on the proposed model, a robust sliding mode controller is designed, simulated and implemented. Lyapunov analysis has been utilized to develop the algorithm for the sliding mode controller. Parameter sensitivity analysis has been also performed to verify the robustness of the controller against parameters uncertainties. Steady-state temperature stability of +/- 0.1 degrees C bound has been satisfied with the temperature rate of up to 3.5 degrees C/s. To validate the entire implemented system, a successful DNA amplification has been performed. The results of the performed laboratory electrophoresis tests on the amplified DNAs affirm the correct amplification of DNAs.