Microfluidic-integrated graphene optical sensors for real-time and ultra-low flow velocity detection

Abstract

As microfluidic technology continues to mature, many techniques are being developed to monitor the flow of microfluidics. However, achieving breakthroughs in the real-time detection of ultra-low flow velocity and non-conductive liquid in microfluidic environments remains a major challenge. Here, microfluidic-integrated graphene optical sensorswith a sensitivity of 4.65 × 105 mV⋅s⋅m−1 and a detection limit of 4.9 × 10−5 m⋅s−1 were designed to address these challenges. We reported our efforts to quantify the impact of ultra-low flow velocity driven by ultra-small levels of pressure. A flow velocity of 3.7 × 10−4 m⋅s−1 was detected with a signal-to-noise ratio of approximately 7.5. A high-quality graphene layer that was directly grown on glass by an improved low-pressure chemical vapor deposition method and provided several advantages, including controllable thickness, high uniformity, high stability, and corrosion resistance. Graphene also has an excellent polarization-dependent effect. It was extremely sensitive to pressure-driven microfluidic flow because of the interaction between polarization light and the quartz glass/graphene film/medium multilayer-coupling structure, which fed back the signals in real-time. This novel sensor represents a breakthrough in the ultra-low level detection of the flow velocity of non-conductive microfluidics. We expect this sensor to have a broad array of applications in the field of microfluid velocity measurement.