Printed Circuit Board-Based Polymerase Chain Reaction Chip

Many reported polymerase chain reaction (PCR) chips include heater patterns fabricated with metal materials (such as copper, aluminum, or gold) printed on the substrate, and their temperatures are measured with patterns made with copper or platinum. Since the fabrication process for silicon based chips is expensive, and that for polymer based chips is highly complicated, the use of well-developed process will be beneficial to PCR chips. In this work, a PCR chip was constructed that uses the well-developed printed circuit board (PCB) fabrication process to the extent possible. In order to heat the chip and measure its temperature, a heater pattern and a circuit for a thermistor were built on the bottom of the double-sided PCB, and a thermal spreading pad was made on the top for uniformity. A substrate was attached on the pad side of the PCB with thermal tape, and the chamber was constructed on the substrate with double-sided tape. A polyethylene terephthalate (PET) film was used to make the cover with the inlet/outlet and the air holes. An 8-bit microcontroller incorporating an analog-to-digital converter (ADC) and pulse width modulation (PWM) modules was employed to control the chip. For heating and cooling of the chip, the heater pattern and a fan beside the PCB were controlled with PWM. The resistance of the smd-type thermistor soldered on the PCB was converted to temperature in digital form, using a voltage divider and the ADC. Various materials for the chamber construction, especially for the substrates, such as cover glass and prevalent plastic and metal tapes, were evaluated and compared with the conventiorial desktop PCR thermocycler.