Abstract
Nanoparticles transported through highly confined porous media
exhibit faster breakthrough than small molecule tracers. Despite important
technological applications in advanced materials, human health, energy, and
environment, the microscale mechanisms leading to early breakthrough have not
been identified. Here, we measure dispersion of nanoparticles at the singleparticle
scale in regular arrays of nanoposts and show that for highly confined
flows of dilute suspensions of nanoparticles the longitudinal and transverse
velocities exhibit distinct scaling behaviors. The distributions of transverse particle velocities become narrower and more non-Gaussian when the particles
are strongly confined. As a result, the transverse dispersion of highly confined nanoparticles at low Péclet numbers is significantly less important than
longitudinal dispersion, leading to early breakthrough. This finding suggests a fundamental mechanism by which to control dispersion and thereby improve
efficacy of nanoparticles applied for advanced polymer nanocomposites, drug delivery, hydrocarbon production, and environmental remediation.
