Optimization of heaters in a digital microfluidic biochip for the polymerase chain reaction

A digital microfluidic biochip (DMFB) is an attractive technology platform for revolutionizing immunoassays, clinical diagnostics, drug discovery, DNA sequencing, and other laboratory procedures in biochemistry. In most of these applications, real-time polymerase chain reaction (PCR) is an indispensable step for amplifying specific DNA segments. Compared with traditional PCR platforms, DMFBs offer the benefits of smaller size, higher sensitivity and quicker time-to-results. Heater design is critical for any on-chip PCR implementation because it is closely related to each step of the PCR. In this paper, we propose a combined electrode/heater structure that can realize the functions of both heating and electrowetting-on-dielectric (EWOD) actuation, and we systematically analyze and compare this heater design to the conventional square-shaped heater. The heating efficiency and thermal response of both the proposed and conventional heater structure are studied through detailed COMSOL Multiphysics simulations. Based on our heater design, a corresponding self-adaptive heating system is also proposed for precise temperature control.