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

摘要

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 nonconductive liquid in microfluidic environments remains a major challenge. Here, microfluidic-integrated graphene optical sensorswith a sensitivity of 4.65 x 10(5) mV.s.m(-1) and a detection limit of 4.9 x 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 x 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 lowpressure 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.