Magnetic resonance imaging of diffusion in micro-structures using diamond quantum sensors

Understanding the diffusion of particles in micro-structures plays a vital role in many fields including neuroscience, cancer- or battery-research. So far non invasive methods able to measure the diffusion on this length scale while maintaining a spatial correlation of the signal are lacking. Here we introduce the nitrogen vacancy (NV) center based nuclear magnetic resonance (NMR) as a novel tool to probe diffusion on the micro-scale. We developed a new experimental setup combining gradient coils, microfluidics, engineered diamonds and imaging of the experiment, improving on the recent achievements of NV-NMR and combining it with the well known pulsed gradient spin echo (PGSE) approach for diffusion measurements. Especially in the field of diamond engineering we achieved major improvements in the coherence time, laser stability and readout contrast, compared to previously cited values. The gain in sensitivity allowed us to probe the diffusion in microfluidic channels and correlate the results spatially using simultaneous optical imaging. The development of this setup and our first experimental results mark a major step towards the development of NV-center based MRI and diffusion-MRI experiments, while the achievements in diamond engineering will benefit the NV-community as a whole.