Droplet microfluidic chip for precise monitoring of dynamic solution changes

In this work, an automated microfluidic chip that uses negative pressure to sample and analyze solutions with high temporal resolution was developed. The chip has a T-shaped channel for mixing the sample with a fluorescent indicator, a flow-focusing channel for generating droplets in oil, and a long storage channel for incubating and detecting the droplets. By monitoring the fluorescence intensity of the droplets, the device could detect changes in solution accurately over time. The chip can generate droplets at frequencies of up to 42 Hz with a mixing ratio of 1:1 and a temporal resolution of 3–6 s. It had excellent linearity in detecting fluorescein solution in the concentration range 1–5 μM. This droplet microfluidic chip provides several advantages over traditional methods, including high temporal resolution, stable droplet generation, and faster flow rates. This approach could be applied to monitoring calcium ions with a dynamic range from 102 to 107 nM and a detection limit of 10 nM.