We have extended the utility of NMR as a technique to probe porous media structure over length scales of approximately 100-2000 microm by using the spin 1/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We utilized Pulsed Gradient Spin Echo NMR measurements of the time-depe...

We study the interplay of pore-scale mixing and network-scale advection through heterogeneous porous media, its role for evolution asymptotic behavior hydrodynamic dispersion. In a Lagrangian framework, we identify three fundamental mechanisms that determine large scale particle motion, namely, smoothing intra-pore velocity contrasts, increase tortuosity paths, setting maximum time transitions....

The matched asymptotic (MA) approach of the coupled criterion (CC) enables studying crack initiation at a pore located near free edge, which leads to competition between three possible mechanisms, namely in ligament, side opposite edge or simultaneously both sides. mechanism that is most likely occur depends on pore-to-free ligament size and material characteristic length diameter ratio. Simult...

We report experimental escape time distributions of double-stranded DNA molecules initially threaded halfway through a thin solid-state nanopore. We find a universal behavior of the escape time distributions consistent with a one-dimensional first passage formulation notwithstanding the geometry of the experiment and the potential role of complex molecule-liquid-pore interactions. Diffusion con...

In this letter, the uniform 4H silicon carbide (SiC) mesopores was fabricated by pulsed electrochemical etching method. The length of the mesopores is about 19 μm with a diameter of about 19 nm. The introduction of pause time (T off) is crucial to form the uniform 4H-SiC mesopores. The pore diameter will not change if etching goes with T off. The hole concentration decreasing at the pore tips d...

Bone tissue engineering scaffolds should be designed to optimize mass transport, cell migration, and mechanical integrity to facilitate and enhance new bone growth. Although many scaffold parameters could be modified to fulfill these requirements, pore size is an important scaffold characteristic that can be rigorously controlled with indirect solid freeform fabrication. We explored the effect ...

Compacted clays are considered as excellent candidates for barriers to radionuclide transport in future repositories for nuclear waste due to their very low hydraulic permeability. Diffusion is the dominant transport mechanism, controlled by a nano-scale pore system. Assessment of the clays' long-term containment function requires adequate modelling of such pore systems and their evolution. Exi...

Porous coordination polymers are well known for their easily tailored framework structures and corresponding properties. Although systematic modulations of pore sizes of binary prototypes have gained great success, simultaneous adjustment of both pore size and shape of ternary prototypes remains unexplored, owing to the difficulty in controlling the self-assembly of multiple molecular building ...

An apparatus that integrates solid-state nanopore ionic current measurement with a scanning-probe microscope is developed. When a micrometer-scale scanning-probe tip is near a voltage-biased nanometer-scale pore (10–100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the l...

We study the passage times of a translocating polymer of length N in three dimensions, while it is pulled through a narrow pore with a constant force F applied to one end of the polymer. At small to moderate forces, satisfying the condition FN(nu)/k(B)T less, similar 1, where nu approximately 0.588 is the Flory exponent for the polymer, we find that tau(N), the mean time the polymer takes to le...