Volumetric, Microfluidic Plasmonic RT‐PCR

Abstract Decentralized molecular detection of pathogens remains an important goal for public health. Although polymerase chain reaction (PCR) remains the gold‐standard molecular detection method, thermocycling using Peltier heaters presents challenges in decentralized settings. Recent work has demonstrated plasmonic PCR, where nanomaterials on a surface or nanoparticles in solution heat upon stimulation by light, as a promising method for rapid thermocycling. Heating of a solution via nanoparticles suspended in solution has been demonstrated in PCR tubes, but not on microfluidic chips. We developed a volumetric, microfluidic plasmonic reverse transcription (RT)‐PCR method. A microfluidic chip is fabricated with an integrated thermocouple to measure internal temperature, feeding into a proportional‐integral‐derivative (PID) algorithm that modulates an infrared LED for closed‐loop control. Gold nanorods are dispersed in solution with RT‐PCR reagents. We created an instrument for plasmonic RT‐PCR using an infrared LED for heating, fan for cooling, and fluorometer for end‐point fluorescence detection. Rapid thermocycling and amplification of SARS‐CoV‐2 within 16 min (5 min for RT, 45 cycles in 11 min) is achieved. This paper demonstrates volumetric, plasmonic PCR in a microfluidic chip, using an integrated thermocouple for closed‐loop control. This work points to the promise of using microfluidics and nanomaterials to achieve rapid, compact detection of pathogens in decentralized settings.