Highly Sensitive Detection of Physiological Spins in a Microfluidic Device

Sensing and imaging paramagnetic species under physiological conditions is a key technology in chemical and biochemical analytics, cell biology, and medical sciences. At submicrometer length scales, nitrogen-vacancy (NV) centers in diamond offer atom-sized probes for magnetic fields. We show that spin relaxation of an ensemble NV sensor allows sensing of adsorbed and freely diffusing manganese­(II) ions and adsorbed ferritin. Sensitivities approach 175 Mn ions and 10 ferritin proteins per diffraction limited spot under ambient conditions.