0

IN THIS ISSUE

### Research Papers

J. Nanotechnol. Eng. Med. 2014;5(3):031001-031001-8. doi:10.1115/1.4028695.
FREE TO VIEW

We aimed to investigate 3,5,3′-triiodothyroacetic acid (TRIAC) effects on intact and atrophic skin induced by glucocorticoids (GCs) in rats and the effects induced by nanoencapsulation. The effects of TRIAC and nanoencapsulated TRIAC were evaluated on intact and atrophic skin in TRIAC experiment and nanoencapsulated TRIAC experiment, respectively. Both experiments had two phases: phase I, cutaneous atrophy was induced; phase II, TRIAC or nanoencapsulated TRIAC was administrated. Our results showed that topical use of TRIAC with or without nanoencapsulation was able to reverse cutaneous atrophy. Nanoencapsulated TRIAC showed less systemic changes than TRIAC; therefore, it is possibly a safer drug for topical administration.

Topics: Skin , Vehicles , Drugs
Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031002-031002-7. doi:10.1115/1.4028732.
FREE TO VIEW

Ocular drug delivery is a complex and challenging process and understanding the transport characteristics of drug-loaded particles is very important for designing safe and effective ocular drug delivery devices. In this paper, we investigated the effect of the microchannel configuration of the microdevice, the size of drug-loaded nanoparticles (NPs), and the pressure gradient of fluid flow in determining the maximum number of NPs within a certain outlet region and transportation time of drug particles. We employed a hybrid computational approach that combines the lattice Boltzmann model for fluids with the Brownian dynamics model for NPs transport. This hybrid approach allows to capture the interactions among the fluids, NPs, and barriers of microchannels. Our results showed that increasing the pressure gradient of fluid flow in a specific type of microchannel configuration (tournament configuration) effectively decreased the maximum number of NPs within a certain outlet region as well as transportation time of the drug loaded NPs. These results have important implications for the design of ocular drug delivery devices. These findings may be particularly helpful in developing design and transport optimization guidelines related to creating novel microchannel configurations for ocular drug delivery devices.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031003-031003-5. doi:10.1115/1.4028855.
FREE TO VIEW

This paper describes the inner workings of centrioles (a pair of small organelles adjacent to the nucleus) as they create cell electropolarity, engage in cell division (mitosis), but in going awry, also promote the development of cancers. The electropolarity arises from vibrations of microtubules composing the centrioles. Mitosis begins as each centrioles duplicates itself by growing a daughter centriole on its side. If during duplication more than one daughter is grown, cancer can occur and the cells divide uncontrollably. Cancer cells with supernumerary centrioles have high electropolarity which can serve as an attractor for charged therapeutic nanoparticles.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031004-031004-5. doi:10.1115/1.4029029.
FREE TO VIEW

Increased ignition probabilities of ethanol are found on a heated hot-plate with the introduction of Al2O3, Fe3O4, and carbon nanotube (CNT) nanoparticle suspensions. We show that the mechanism is probably due to liquid fuel boiling point elevation caused by nanoparticle accumulation at liquid–vapor interfaces. The magnitudes of this impact are related to the number and geometry of nanoparticles but independent from the nanoparticle chemical compositions. These findings may have important applications for developing future alternative liquid fuels with advanced combustion characteristics.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031005-031005-5. doi:10.1115/1.4029161.
FREE TO VIEW

A high throughput manufacturing process to magnetically assembling nanowire (NW) network into paraffin was developed for enhancing conductivity in phase change materials (PCMs) used in energy storage applications. The prefabricated nickel NWs were dispersed in melted paraffin followed by magnetic alignment under a strong magnetic field. Measuring electrical conductivity of the nanocomposite, as well as observing cross section of the sample slice under an optical microscope characterized the alignment of NWs. As a comparison, nickel particles (NPs) based paraffin nanocomposites were also fabricated, and its electrical conductivity with and without applied magnetic field were measured. The effects of aspect ratio of fillers (particles and NWs) and volume concentration on percolation threshold were studied both experimentally and theoretically. It was found that the NW based paraffin nanocomposite has much lower percolation threshold compared to that of particle based paraffin composite. Furthermore, the alignment of particles and NWs under magnetic field significantly reduces the threshold of percolation. This work provides solid foundation for the development of a manufacturing technology for high thermal conductivity PCMs for thermal energy storage applications.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031006-031006-5. doi:10.1115/1.4029414.
FREE TO VIEW

The two phase polymer composites have been extensively used in various structural applications; however, there is need to further enhance the strength and stiffness of these polymer composites. Carbon nanotubes (CNTs) can be effectively used as secondary reinforcement material in polymer based composites due to their superlative mechanical properties. In this paper, effects of multiwall nanotubes (MWNTs) reinforcement on epoxy–carbon polymer composites are investigated using experiments. MWNTs synthesized by chemical vapor deposition (CVD) technique and amino-functionalization are achieved through acid-thionyl chloride route. Diglycidyl ether of bisphenol-A (DGEBA) epoxy resin with diethyl toluene diamine (DETDA) hardener has been used as matrix. T-300 carbon fabric is used as the primary reinforcement. Three types of test specimen of epoxy–carbon composite are prepared with MWNT reinforcement as 0%, 1%, and 2% MWNT (by weight). The resultant three phase nanocomposites are subjected to tensile test. It has been found that both tensile strength and strain at failure are substantially enhanced with the small addition of MWNT. The analytical results obtained from rule of mixture theory (ROM) shows good agreement with the experimental results. The proposed three phase polymer nanocomposites can find applications in composite structures, ballistic missiles, unmanned arial vehicles, helicopters, and aircrafts.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031007-031007-7. doi:10.1115/1.4029462.
FREE TO VIEW

Due to their superior mechanical and electrical properties, multiwalled carbon nanotubes (MWCNTs) have the potential to be used in many nano-/micro-electronic applications, e.g., through silicon vias (TSVs), interconnects, transistors, etc. In particular, use of MWCNT bundles inside annular cylinders of copper (Cu) as TSV is proposed in this study. However, the significant difference in scale makes it difficult to evaluate the interfacial mechanical integrity. Cohesive zone models (CZM) are typically used at large scale to determine the mechanical adherence at the interface. However, at molecular level, no routine technique is available. Molecular dynamic (MD) simulations is used to determine the stresses that are required to separate MWCNTs from a copper slab and generate normal stress–displacement curves for CZM. Only van der Waals (vdW) interaction is considered for MWCNT/Cu interface. A displacement controlled loading was applied in a direction perpendicular to MWCNT's axis in different cases with different number of walls and at different temperatures and CZM is obtained for each case. Furthermore, their effect on the CZM key parameters (normal cohesive strength $(σmax)$ and the corresponding displacement $(δn)$ has been studied. By increasing the number of the walls of the MWCNT, $σmax$ was found to nonlinearly decrease. Displacement at maximum stress, $δn$, showed a nonlinear decrease as well with increasing the number of walls. Temperature effect on the stress–displacement curves was studied. When temperature was increased beyond 1 K, no relationship was found between the maximum normal stress and temperature. Likewise, the displacement at maximum load did not show any dependency to temperature.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031008-031008-11. doi:10.1115/1.4029079.
FREE TO VIEW

The degree of variability between theoretical and empirical nanofluid viscosity model predictions and relevant experimental data is examined in this work. Results confirm a high degree of variability in the compared data; with some observed inconsistencies in the model formulations and the predicted data, consequently, a range of constitutive factors need to be incorporated into the models in order to accurately predict the rheological behavior of nanofluids in different use conditions. Notably, conducting broad theoretical studies and empirical investigations into the rheological behavior of nanofluids incorporating the fundamental parametric variables can plausibly lead to near-generalized models.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2014;5(3):031009-031009-8. doi:10.1115/1.4029628.
FREE TO VIEW

Manipulating suspended neutrally buoyant colloidal particles of radii a = O (0.1–1 μm) near solid surfaces, or walls, is a key technology in various microfluidics devices. These particles, suspended in an aqueous solution at rest near a solid surface, or wall, are subject to wall-normal “lift” forces described by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory of colloid science. The particles experience additional lift forces, however, when suspended in a flowing solution. A fundamental understanding of such lift forces could therefore lead to new methods for the transport and self-assembly of particles near and on solid surfaces. Various studies have reported repulsive electroviscous and hydrodynamic lift forces on colloidal particles in Poiseuille flow (with a constant shear rate $γ·$ near the wall) driven by a pressure gradient. A few studies have also observed repulsive dielectrophoretic-like lift forces in electroosmotic (EO) flows driven by electric fields. Recently, evanescent-wave particle tracking has been used to quantify near-wall lift forces on a = 125–245 nm polystyrene (PS) particles suspended in a monovalent electrolyte solution in EO flow, Poiseuille flow, and combined Poiseuille and EO flow through ∼30 μm deep fused-silica channels. In Poiseuille flow, the repulsive lift force appears to be proportional to $γ·$, a scaling consistent with hydrodynamic, versus electroviscous, lift. In combined Poiseuille and EO flow, the lift forces can be repulsive or attractive, depending upon whether the EO flow is in the same or opposite direction as the Poiseuille flow, respectively. The magnitude of the force appears to be proportional to the electric field magnitude. Moreover, the force in combined flow exceeds the sum of the forces observed in EO flow for the same electric field and in Poiseuille flow for the same $γ·$. Initial results also imply that this force, when repulsive, scales as $γ·1/2$. These results suggest that the lift force in combined flow is fundamentally different from electroviscous, hydrodynamic, or dielectrophoretic-like lift. Moreover, for the case when the EO flow opposes the Poiseuille flow, the particles self-assemble into dense stable periodic streamwise bands with an average width of ∼6 μm and a spacing of 2–4 times the band width when the electric field magnitude exceeds a threshold value. These results are described and reviewed here.

Commentary by Dr. Valentin Fuster

### Technical Brief

J. Nanotechnol. Eng. Med. 2014;5(3):034501-034501-4. doi:10.1115/1.4029158.
FREE TO VIEW

Molecular dynamics (MD) simulation aiming to investigate heat transfer between argon fluid flow and two parallel copper plates in the nanoscale is carried out by simultaneously control momentum and temperature of the simulation box. The top copper wall is kept at a constant velocity by adding an external force according to the velocity difference between on-the-fly and desired velocities. At the same time the top wall holds a higher temperature while the bottom wall is considered as physically stationary and has a lower temperature. A sample region is used in order to measure the heat flux flowing across the simulation box, and thus the heat transfer coefficient between the fluid and wall can be estimated through its definition. It is found that the heat transfer coefficient between argon fluid flow and copper plate in this scenario is lower but still in the same order magnitude in comparison with the one predicted based on the hypothesis in other reported work.

Commentary by Dr. Valentin Fuster