Effect of solution conductivity and electrode shape on the deposition of carbon nanotubes from solution using dielectrophoresis

Dielectrophoresis (DEP) is a popular technique for fabricating carbon nanotube (CNT) devices. The electric current passing through the solution during DEP creates a temperature gradient, which results in electrothermal fluid flow because of the presence of the electric field. CNT solutions prepared with various methods can have different conductivities and the motion of the solution because of the electrothermal phenomenon can affect the DEP deposition differently in each case. We investigated the effect of this movement in solutions with various levels of conductivity through experiments as well as numerical modeling. Our results show that electrothermal motion in the solution can alter the deposition pattern of the nanotubes drastically for high conductivity solutions, while DEP remains the dominant force when a low conductivity (surfactant-free) solution is used. The extent of effectiveness of each force is discussed in the various cases and the fluid movement model is investigated using two- and three-dimensional finite element simulations.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofUnreviewedFacult

First-principles study of field-emission from carbon nanotubes in the presence of methane

Carbon nanotubes are promising candidates for field-emitters. It has been shown that the presence of various gases can enhance or degrade the performance of nanotube emitters. Small hydrocarbons are of particular interest because of their ability to enhance the emission properties. The authors report a simulation study of field-emission from a carbon nanotube exposed to methane in various configurations with an emphasis on calculating the emission current. The Hartree–Fock theory combined with a Green’s functions approach was used for the simulations. It was observed that the change in the emission current strongly depends on the particular arrangement of the methane molecules on the nanotube.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofReviewedFacult

Synthesis of novel nanostructured bredigite-amoxicillin scaffolds for bone defect treatment: cytocompatibility and antibacterial activity

Bone infections in human beings are an essentially destructive problem with crucial clinical and economic effects; thus, incorporation of antibiotics such as amoxicillin (AMX) into the scaffold was developed as an effective treatment for bone infections. In this respect, we develop new nanostructured bredigite (Bre; Ca7MgSi4O16)–amoxicillin (AMX; α-amino-hydroxybenzyl-penicillin) scaffolds containing different concentrations of amoxicillin (0, 3, 5, and 10%) by using space holder method to assure bactericidal properties. The result depicted that the Bre–AMX scaffolds possess porosity of 80–82% with high compressive strength of 1.2–1.4 MPa and controlled antibiotic release for prevention of infection. Bre–(3–10%)AMX scaffolds were able to destroy Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria, as well as effectively inhibit the growth of bacterial cells; in addition, the antibacterial activity of the AMX-loaded scaffolds augmented with the increase of the AMX concentration. Sustained drug release was detected from Bre–AMX scaffolds accompanied by initial burst release of 20% for 8 h, followed by a sustained release, which is favorable for bone infection treatment. These new Bre–(3–5%)AMX scaffolds possess excellent mechanical properties and antibacterial activity with no cytotoxicity suggested as an appropriate alternative for bone infection treatment

Drug delivery and cytocompatibility of ciprofloxacin loaded gelatin nanofibers-coated Mg alloy

In this study, gelatin-ciprofloxacin (Gel-Cip) nanofibers containing various amounts of Cip (0, 2, 4 and, 8 wt%) were fabricated on the surface of Mg-1Ca alloy via an electrospinning process. Microscopic characterization indicated a porous network structure with fiber diameters in the range of 150–170 nm. Prolonged drug release was attained from Gel-Cip nanofibers coating along with initial rapid drug release of around 20–22% during 12 h, followed by a slow release stage that can effectively control the infection. The incorporation of 2–4 wt% Cip into Gel nanofibers coating significantly increased the antibacterial performance and corrosion resistance of the uncoated Mg-Ca alloy without showing an inhibitory influence on the cytocompatibility characteristic. Hence, it is potentially appropriate as the novel electrospun nanofibers coating material for bone regeneration application

Novel nanostructured baghdadite-vancomycin scaffolds: in-vitro drug release, antibacterial activity and biocompatibility

One of the most important therapeutic and economic concerns regarding surgery, is the occurrence of post-operative infections which leads to an increase in premature failure rate. Therefore, novel nanostructured baghdadite-vancomycin (Ba-Vac) scaffolds were prepared using the space holder method with good mechanical properties and controlled drug release to inhibit post-surgery infections. The results showed that the (Ba-Vac) scaffolds were attained with the pore size of 300–400 µm and total porosity of 80–82% with compressive strength of 0.86–0.88 MPa. In drug release profiles, a burst release was observed for 6 h, followed by a sustained release. Ba-Vac scaffolds presented good antibacterial activity toward Staphylococcus aureus (S. aureus). More attachment and spreading of MG-63 osteoblast cells on the Ba and Ba-(1-3 wt%)Vac scaffolds was also observed in comparison with the Ba-5 wt%Vac scaffold. Therefore, the Ba-(1–3 wt%)Vac scaffold is a good candidate for inhibiting post-surgery infections, as well as for bone tissue engineering