Paper-based resistive heater with accurate closed-loop temperature control for microfluidics paper-based analytical devices

Accurate temperature controlling system is essential for temperature-sensitive applications of microfluidics technology. In this paper, for the first time, we implemented a low-cost temperature controlling system on paper to be used in paper-based microfluidics. A resistive heater was fabricated by screen-printing of conductive electric paint on paper substrate. The temperature was measured by a non-contact temperature sensor to suppress the effect of contact sensors’ thermal mass on the measured temperature. By utilizing PID controller in a closed-loop system, the accuracy of temperature is below 0.22 °C which is suitable for biological temperature-sensitive applications. A microfluidics paper-based analytical device (µPAD) is fabricated by screen-printing on filter paper and attached to the heater to be used as device under test. The fabrication and implementation procedures of the whole system including the heater, the temperature controller and the µPAD are very low-cost, fast and simple. The operation of the fabricated heater and the temperature controlling system were validated by a temperature-sensitive colorimetric test of cholesterol.