The biocompatibility of carbon nanotubes

Journal of Applied physics,Vol.33 : 1962年に発表されたレオロジー関連の論文

Pressure-driven water flow through carbon nanotubes (CNTs) with diameters ranging from 1.66 to 4.99 nm is examined using molecular dynamics simulation. The flow rate enhancement, defined as the ratio of the observed flow rate to that predicted from the no-slip Hagen-Poiseuille relation, is calculated for each CNT. The enhancement decreases with increasing CNT diameter and ranges from 433 to 47. By calculating the variation of water viscosity and slip length as a function of CNT diameter, it is found that the results can be fully explained in the context of continuum fluid mechanics. The enhancements are lower than previously reported experimental results, which range from 560 to 100 000, suggesting a miscalculation of the available flow area and/or the presence of an uncontrolled external driving force (such as an electric field) in the experiments.

Reassessing fast water transport through carbon nanotubes.

Nanoscale carbon tubes and pipes can be readily fabricated using self-assembly techniques and they have useful electrical, optical and mechanical properties. The transport of liquids along their central pores is now of considerable interest both for testing classical theories of fluid flow at the nanoscale and for potential nanofluidic device applications. In this review we consider evidence for novel fluid flow in carbon nanotubes and pipes that approaches frictionless transport. Methods for controlling such flow and for creating functional device architectures are described and possible applications are discussed.

Fluid flow in carbon nanotubes and nanopipes.

Nanoscale carbon tubes and pipes can be readily fabricated using self-assembly techniques and they have useful electrical, optical and mechanical properties. The transport of liquids along their central pores is now of considerable interest both for testing classical theories of flfl ow at the nanoscale and for potential nanofl uidic device applications. In this review we consider evidence for novel fl uid fl ow in carbon nanotubes and pipes that approaches frictionless transport. Methods for controlling such fl ow and for creating functional device architectures are described and possible applications are discussed.

Fluid fl ow in carbon nanotubes and nanopipes

A simple technique to simultaneously induce fluid flow through an individual nanopipe and measure the flow rate and the pressure difference across the pipe is described. Two liquid drops of different sizes are positioned at the two ends of the nanopipe. Due to the higher capillary pressure of the smaller drop, flow is driven from the smaller drop to the bigger drop. The instantaneous pressures of the two drops are estimated from the drops’ shapes and sizes. The flow rate is estimated by monitoring the sizes of the drops as functions of time with a microscope and a video camera. A theory that correlates the drops’ sizes and the flow rate is derived. Measurements are carried out with an ionic salt and glycerin to estimate the effective tube radius of the nanopipes with diameters ranging from 200 to 300nm. The tubes’ diameters are independently measured with a scanning electron microscope. The method is also verified by tracking the motion of fluorescent particles through the nanopipe. The paper provides a s...

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Induction and measurement of minute flow rates through nanopipes

The condensation of water inside multiwalled carbon nanotubes has been monitored and controlled using environmental scanning electron microscopy. Undersaturated vapor condenses inside nanotubes and forms nanometer-thick water films. Simultaneously, nanotubes deform and decrease their apparent diameter. When the vapor pressure in the chamber approaches the saturation pressure, we observe the formation of menisci and spontaneous buckling of the nanotubes. We derive a criterion of the buckling instability caused by capillary condensation. Remarkably, the buckling criterion appears to be independent of the meniscus shape. Using our experiments and models, we estimated the circumferential Young's modulus of large-diameter carbon nanotubes with disordered wall structure produced by the chemical vapor deposition method (CVD) to be E(thetatheta) approximately 13-18 MPa. It appears to be at least 2 orders of magnitude lower than the longitudinal modulus of nanotubes produced by arc discharge or catalytic CVD methods. The reported experiments and proposed theory suggest possible applications of "soft" nanotubes as sensors to probe minute concentrations of absorbable gases and vapors.

Deformation of Carbon Nanotubes by Exposure to Water Vapor

The targeted bipolar electrodeposition of polypyrrole was carried out onto the tips of hydrophilic carbon nanopipes. By aligning an external electric field relative to the nanopipes, the deposition of polypyrrole onto selected ends could be achieved without physically contacting the nanopipes. After deposition, carbon nanopipes with both partially open and fully blocked tips were found. Experiments conducted in an environmental scanning electron microscope showed that water enters the nanopipes through the tip with polypyrrole due to the higher hydrophilicity of the polymer compared to the tube walls. As a result, it was possible to guide the entry of water from a specific end of the tube and fill the tube from the selected side. Condensation experiments conducted on nanopipes with polypyrrole on both tips shows the difference in hydrophilicity of the nanopipes compared to the polypyrrole. The ability to selectively control the site of condensation and uptake of fluid by carbon nanotubes or nanopipes is very important for the development of nanotube-based nanofluidic devices.

Guiding water into carbon nanopipes with the aid of bipolar electrochemistry

The dynamic response—as caused by different means of thermal stimulation or pressurization—of aqueous liquid attoliter volumes contained inside carbon nanotubes is investigated theoretically and experimentally. The experiments indicate an energetically driven mechanism responsible for the dynamic multiphase fluid behavior visualized in real time with high spatial resolution using electron microscopy. The theoretical model is formulated using a continuum approach, which combines temperature-dependent mass diffusion with intermolecular interactions in the fluid bulk, as well as in the vicinity of the carbon walls. Intermolecular forces are modeled by Lennard-Jones potentials. Several one-dimensional and axisymmetric cases are considered. These include situations which physically represent liquid volume pinchoff, jetting, or fluid relocation due to thermal stimulation by a steady or modulated electron beam, as well as liquid precipitation (condensation) from vapor due to overcooling or pressurization. Comparisons between theoretical predictions and experimental data demonstrate the ability of the model to describe the characteristic trends observed in the experiments.

Theoretical and experimental investigation of aqueous liquids contained in carbon nanotubes

Potential biomedical applications for carbon nanofibres include, but are not limited to, biosensors and drug delivery vehicles. For such applications, it is essential to know how carbon nanotubes interact with antibodies and proteins. We report on the successful adsorption of monoclonal CD3 antibodies on two types of carbon nanofibre produced by the same method and having the same average size and shape, but differing in surface structure and chemistry due to dissimilar post-treatments. Binding of proteins to nanofibres is enhanced by poly (L-lysine) (PLL) and improves with increasing disorder and hydrophilicity of the nanofibres' surface. Oxidized and disordered surfaces of pyrolytically stripped nanofibres show improved wetting and attachment of PLL and proteins compared to hydrophobic and well-ordered surfaces of heat-treated nanofibres. These results show that the surface of carbon nanofibres can be tailored for their use in biomedical applications.

https://iopscience.iop.org/article/10.1088/0957-4484/16/4/038/pdf

Maria Pia Rossi

Papers

Induction and measurement of minute flow rates through nanopipes

Deformation of Carbon Nanotubes by Exposure to Water Vapor

Guiding water into carbon nanopipes with the aid of bipolar electrochemistry

Theoretical and experimental investigation of aqueous liquids contained in carbon nanotubes

Effect of carbon nanofibre structure on the binding of antibodies