Continuous gradient temperature control of microfluidic chip based on thermoelectric cooler

High-efficiency and accurate temperature control is the key to the application of microfluidic technology in biology, chemistry and medicine fields. At present, gradient temperature control of microfluidic chip in a wide range below room temperature still faces challenges. Based on a microfluidic platform of double emulsion droplets, this study builds a temperature control system and attempts to achieve continuous gradient temperature control on time scale of microfluidics based on thermoelectric cooler. Temperature control unit is designed and relevant control strategies are discussed to achieve accurate temperature control. Meanwhile, the strategy to achieve continuous gradient temperature control of microfluidic chip is mainly explored. Finally, combining with the working characteristics of thermoelectric cooler, continuous gradient temperature control of microfluidic chip is experimentally realized based on adaptive fuzzy PID control, while PID control shows remarkable overshoot, deviation and oscillation. Moreover, small gradient temperature control from 10 °C down to −15 °C, −20 °C and then −25 °C is precisely realized by using adaptive fuzzy PID control, as well as large gradient temperature control from 20 °C down to 0 °C and then −20 °C. Specifically, the maximum deviation of temperature is 0.192 °C in small gradient temperature control, and the steady state error is within ±0.07 °C. In large gradient temperature control, the maximum deviation of temperature is 0.309 °C, and the steady state error was within ±0.1 °C. This study provides diversified temperature control in a wide range for microfluidic analysis.