Ultrafast water permeation in aquaporins is promoted by their hydrophobic interior surface. Polytetrafluoroethylene has a dense fluorine surface, leading to its strong water repellence. We report a series of fluorous oligoamide nanorings with interior diameters ranging from 0.9 to 1.9 nanometers. These nanorings undergo supramolecular polymerization in phospholipid bilayer membranes to form fluorous nanochannels, the interior walls of which are densely covered with fluorine atoms. The nanochannel with the smallest diameter exhibits a water permeation flux that is two orders of magnitude greater than those of aquaporins and carbon nanotubes. The proposed nanochannel exhibits negligible chloride ion (Cl – ) permeability caused by a powerful electrostatic barrier provided by the electrostatically negative fluorous interior surface. Thus, this nanochannel is expected to show nearly perfect salt reflectance for desalination.

Liquid wetting of a surface is omnipresent in nature and the advance of micro-fabrication and assembly techniques in recent years offers increasing ability to control this phenomenon. Here, we identify how surface roughness influences the initial dynamic spreading of a partially wetting droplet by studying the spreading on a solid substrate patterned with microstructures just a few micrometers in size. We reveal that the roughness influence can be quantified in terms of a line friction coefficient for the energy dissipation rate at the contact line, and that this can be described in a simple formula in terms of the geometrical parameters of the roughness and the line-friction coefficient of the planar surface. We further identify a criterion to predict if the spreading will be controlled by this surface roughness or by liquid inertia. Our results point to the possibility of selectively controlling the wetting behavior by engineering the surface structure.

Osmosis is fundamental to many processes, such as in the function of biological cells and in industrial desalination to obtain clean drinking water. The choice of solute in industrial applications of osmosis is highly important in maximizing efficiency and minimizing costs. The macroscale process of osmosis originates from the nanoscale properties of the solvent, and therefore an understanding of the mechanisms of how these properties determine osmotic strength can be highly useful. For this reason, we have undertaken molecular dynamics simulations to systematically study the influence of ion size and charge on the strength of osmosis of water through carbon nanotube membranes. Our results show that strong osmosis occurs under optimum conditions of ion placement near the region of high water density near the membrane wall and of maintenance of a strong water hydration shell around the ions. The results in turn allow greater insight into the origin of the strong osmotic strength of real ions such as NaCl. Finally, in terms of practical simulation, we highlight the importance of avoiding size effects that can occur if the simulation cell is too small.

The flow of a model non-polar liquid through small carbon nanotubes is studied using non-equilibrium molecular dynamics simulation. We explain how a membrane of small-diameter nanotubes can transport this liquid faster than a membrane consisting of larger-diameter nanotubes. This effect is shown to be back-pressure dependent, and the reasons for this are explored. The flow through the very smallest nanotubes is shown to depend strongly on the depth of the potential inside, suggesting atomic separation can be based on carbon interaction strength as well as physical size. Finally, we demonstrate how increasing the back-pressure can counter-intuitively result in lower exit velocities from a nanotube. Such studies are crucial for optimisation of nanotube membranes.

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The poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) composite has been gaining attention as a potential organic thermoelectric material owing to its superior electrical property and low thermal conductivity. Several experiments have recently demonstrated that introduction of high-boiling-point solvents increases optimal charge carrier concentration and leads to high crystallinity, resulting in noticeable improvement of thermoelectric performance. Therefore, much attention has been paid to electrical properties. Understanding of intrinsic heat conduction in PEDOT is also important since the thermal conductivity of bulk polymers is sensitive to macroscopic alignment and transport properties of individual chains. Moreover, thermoelectric performance inversely scales with thermal conductivity. In this work, by molecular dynamics simulations, we have investigated heat conduction in PEDOT chains and evaluated the impact of adsorbed protonic acid on the thermal conductivity of PEDOT. Owing to the quasi-ballistic nature of heat conduction in PEDOT chains, we found that thermal conductivity has strong size dependence and varies from 1–10 W m−1 K−1. Furthermore, we found that the adsorption on PEDOT of toluene sulfonic acid (TSA); a monomer of PSS; suppresses contribution of the long-wavelength phonons to heat conduction. These results suggest that decreasing the length of PEDOT chains in a composite and increasing the surface density of adsorbed TSA molecules are effective methods of reducing the thermal conductivity of the composite, leading to the enhancement of thermoelectric performance.

Using shadow masks prepared by standard microfabrication processes, we fabricated in-plane thermoelectric microdevices (4 mm 9 4 mm) made of bismuth telluride thin films, and evaluated their performance. We used Bi 0.4 Te 3.0 Sb 1.6 as the p-type semiconductor and Bi 2.0 Te 2.7 Se 0.3 as the n-type semiconductor. We deposited p-and n-type thermoelectric thin films on a free-standing thin film of Si 3 N 4 (4 mm 9 4 mm 9 4 lm) on a Si wafer, and measured the output voltages of the microdevices while heating at the bottom of the Si substrate. The maximum output voltage of the thermoelectric device was 48 mV at 373 K.

Adsorption onto carbon nanotube bundles may find use in various applications such as gas preconcentration and separation, and as a result, it is of great interest to study the adsorption properties of such bundles. The adsorption of linear alkanes, with their systematic variation through chain length, is particularly useful to explore the effects of molecular length on adsorption characteristics. We have conducted grand-canonical Monte Carlo simulations of light linear alkanes adsorbing onto closed nanotube bundles to explore these effects in a systematic manner. Our results demonstrate how adsorption into the grooves of the bundle is favored with alignment of the alkanes along the nanotube axis. We describe in detail the effects of competition for adsorption in the grooves and on the bundle as a whole, and highlight how selectivity can be tuned through careful choice of pressure and temperature. Finally, we describe how it is possible to derive a systematic relation between the length of the alkane and its loading on the bundle, and discuss its usefulness in applying ideal adsorbed solution theory (IAST) to predicting competitive mixed adsorption over a wide range of pressures. We also focus in turn on the ability of IAST to capture adsorption-saturation effects.