High-precision chemical quantum sensing in flowing monodisperse microdroplets.

Area of Science:

• Quantum physics
• Chemical sensing
• Microfluidics

Background:

• High-precision chemical detection is crucial for various scientific and technological applications.
• Existing methods often require large sample volumes or lack stability.
• Quantum sensing offers potential for enhanced sensitivity and precision.

Purpose of the Study:

• To develop a high-precision chemical detection method by integrating quantum sensing with droplet microfluidics.
• To demonstrate sensitive detection of paramagnetic ions using nanodiamond quantum sensors.
• To explore the potential of this method for single-cell analysis and bioreactor monitoring.

Main Methods:

• Utilized nanodiamonds (ND) with nitrogen-vacancy (NV) centers as quantum sensors.
• Employed droplet microfluidics for rapid analysis of microdroplets containing analytes.
• Implemented a noise-suppressed optically detected magnetic resonance mode with controlled flow and microwave control of NV spins.

Main Results:

• Achieved detection of analyte-induced signals as low as a few hundredths of a percent of ND fluorescence.
• Demonstrated low limit-of-detection for paramagnetic ions using minimal analyte volumes.
• Exhibited exceptional measurement stability exceeding 10^3 seconds.

Conclusions:

• The integrated quantum sensing and microfluidics method offers a powerful tool for sensitive and stable chemical detection.
• Co-encapsulation of sensors and analytes in droplets enables applications like single-cell metabolomics and real-time intracellular measurements.
• This work advances portable chemical testing, amplification-free assays, and microenvironment chemical imaging.