Development of a multifunctional microfluidic platform for quantum biosensing

In this study, we developed a microfluidic quantum sensing platform that uses nitrogen vacancy (NV) centers in nanodiamonds to probe temperature and magnetic fields in a controlled fluid environment. The scheme integrates oil-immersion microscopy, optical tweezers, fluorescent imaging, and optically detected magnetic resonance (ODMR) imaging of NV centers in nanodiamond. To characterize the performance of this device, we fabricated an integrated microstripline that produces magnetic and temperature gradients at scales relevant to single cell biosensing. We flowed nanodiamond suspended in water into the microfluidic channel and measured the local magnetic field and change in temperature around the microstripline using NV centers as a quantum spin probe. We obtained magnetic field sensitivity of 60 µT/√Hz and temperature changes on the order of 1^○C. The protocol presented here provides a non-toxic, non-invasive and high-resolution quantum sensing platform, which may be further optimized to map out magnetic fields generated by neuronal activity or temperature gradients in a living cell.