Simultaneous size and ζ-potential measurements of individual nanoparticles in dispersion using size-tunable pore sensors.

The prospect of characterizing individual nanoparticles, molecules, or DNA base pairs has generated considerable interest in resistive pulse sensing. In addition to size and concentration analysis, this technique also has the capacity to measure the charge density of objects in situations where electrophoretic forces dominate their motion. Here we present a methodology to simultaneously extract, via appropriate theoretical models, the size and ζ-potential of objects from the resistive pulse signal they generate. The methodology was demonstrated using a size-tunable elastic pore sensor to measure a complex "bimodal" suspension composed of two particle sets with different size and charge. Elastically tuning the size of the pore sensor, by stretching the elastic pore membrane, enables a larger sample size range to be analyzed, improves measurement sensitivity, and fine-tunes the forces acting on objects. This methodology represents a new approach for investigating and understanding the fundamental behavior of nanoscale dispersions.