A Rapid and Power-Efficient Laser-Induced Graphene Micro-Thermocycler for DNA Polymerase Chain Reaction

Abstract

By amplifying millions or billions of copies of a DNA’s specific segment, polymerase chain reaction (PCR) has a wide range of applications in DNA cloning, forensics, medical, and infectious disease detection. As a result, the technology is becoming more and more widespread as the COVID-19 pandemic pushes for the need for rapid nucleic acid testing, and for early diagnosis compared to antigens testing. This research aims to develop a laser induced graphene (LIG) heater as the heating element for PCR point-of-care testing (POCT), as the PCR detection result is highly dependent on following a specific reagent heating cycle. In particular, the LIG heater can be integrated directly on a polymeric film by laser scribing in one step, eliminating the need for photolithography or chemical vapor deposition, and the entire device can be fabricated in under 5 minutes. This work investigates the heating performance of the LIG heater, by both Ansys Fluent simulation and actual experimentations. To efficiently control the thermal cycling, a LabVIEW program is constructed to obtain the voltage, temperature, and electrical current of the device, and it is highly adjustable to obtain the maximum heat ramp rate of 11.2 °C/s, and cooling rate of 10.8 °C/s in ambient condition. As a result, the thermocycler requires approximately 510 mW to maintain at 95 °C, with an accuracy of ±0.18 °C. Moreover, the device has shown high stability after 24 hours of repeated thermal cycling, with the average power consumption goes from 365 mW to 368 mW. With low power consumption and rapid fabrication, LIG shows great potential not only for PCR heating elements but also for chemical, gas sensors, flexible electronics, and various other applications.