Seeing Chemicals in Blood: Advances in Optical Sensors Based on Oil Droplets

We have developed two fluidic platforms that utilize specially formulated oil droplets as optical sensors for analyzing blood chemistry. The first platform, pressure-driven droplet microfluidics, continuously generates sub-nanoliter oil droplets to enable the chemical analysis of equally small aqueous samples. By preloading arrays of sensing oils and controlling their flow, this system allows for real-time, multi-analyte monitoring, making it a promising tool for bedside critical care applications in hospitals. The second platform, push-pull millifluidics, integrates a microliter-sized liquid channel with a stepper motor to facilitate controlled extraction between an oil segment and an aqueous sample. Designed for portability and affordability, this system offers a practical solution for diagnosing and managing chronic diseases in home and small-clinic settings. Unlike traditional optical sensors, these fluidic platforms uniquely enable the independent tracking of optical signals from the sensor phase, sample phase, and interface. Leveraging fluorescence and absorbance detection in the sensor phase, we have successfully performed chemical analyses on complex biological samples, including whole blood.