Nanodiamond Sensing in Dynamic Environments With Fast‐Tracking Through Four‐Point Positioning

ABSTRACT Nitrogen‐vacancy (NV) centers in nanodiamonds are excellent nanoscale sensors for measuring parameters such as temperature, magnetic field, and viscosity in complex fluidic environments, including living cells. However, the rapid motion imposes a significant challenge for continuous, real‐time tracking and sensing measurements. Here, we present a fast single particle tracking (SPT) method featuring a tetrahedral detection geometry for time‐efficient parallel fluorescence collection using four avalanche photodiodes (4‐APDs). This approach eliminates the temporal latency of traditional sequential scanning, achieving an order of magnitude improvement in the temporal resolution and the upper limit of the measurable diffusion coefficient compared to previously reported methods based on a single APD. The SPT is integrated with multi‐parameter quantum sensing based on optically detected magnetic resonance (ODMR) of NV centers. The sensitivities of ODMR‐based temperature and 3D rotation sensing are evaluated at different diffusion coefficients, which shows no significant degradation within our measurement range. We apply the system for thermorheology measurements in glycerol/water mixtures under thermal ramps. Additionally, we perform simultaneous translation and rotation tracking in live cells, revealing correlated translational and rotational dynamics. This approach advances multi‐parameter nanoscale sensing for soft matter and biological applications, paving the way for real‐time nanoscale sensing in highly dynamic fluidic environments.