Measuring mass of nanoparticles and viruses in liquids with nanometer-scale pores

Nanopores have recently been developed for the detection and physical characterization of nanoparticles, viruses, proteins, nucleic acids, and other macromolecules in liquids. The method provides the ability to rapidly estimate the size and electrical charge of analytes over a wide range of concentration, potentially with small sample volumes and low cost. Here, we use the technique to measure the mass of nanoparticles and viruses and their sedimentation. The analyte sedimentation-time measurement provides an estimate for the nanoparticle mass-density. We also show that the method can be used with samples at low concentration and in small volumes.