Deposition of photocatalytically active TiO2 films by inkjet printing of TiO2 nanoparticle suspensions obtained from microwave-assisted hydrothermal synthesis.

In this paper, we present an inkjet printing approach suited for the deposition of photocatalytically active, transparent titanium oxide coatings from an aqueous, colloidal suspension. We used a bottom-up approach in which a microwave-assisted hydrothermal treatment of titanium propoxide aqueous solutions in the presence of ethylenediaminetetraacetic acid and triethanolamine was used to create suspensions containing titania nanoparticles. Different inkjet printing set-ups, electromagnetic and piezoelectric driven, were tested to deposit the inks on glass substrates. The presence of preformed titania nanoparticles was expected to make it possible to reduce the heating temperature necessary to obtain the functionality of photocatalysis which can widen the application range of the approach to heat-sensitive substrates. We investigated the crystallinity and size of the obtained nanoparticles by electron microscopy and dynamic light scattering. The rheological properties of the suspensions were evaluated against the relevant criteria for inkjet printing and the jettability was analyzed. The photocatalytic activity of the obtained layers was analyzed by following the decomposition of a methylene blue solution under UV illumination. The influence of the heat treatment temperature on the film roughness, thickness and photocatalytic activity was studied. Good photocatalytic performance was achieved for heat treatments at temperatures as low as 150 °C, introducing the possibility of using this approach for heat-sensitive substrates.

Electromagnetic characterization of carbon nanotube films subject to an oxidative treatment at elevated temperature.

Electromagnetic characterization of CNT films fabricated by thermal decomposition of SiC has been performed. Purification and/or uncapping treatment conditions at an elevated temperature of 400 degrees C under flowing oxygen or carbon dioxide have been studied. A near field microwave microscope was used to measure the real and imaginary parts of the complex permittivity of CNT films through the frequency shift and the change in reciprocal quality factor between two extreme positions of an evanescent microwave probe-tip (in contact with the sample, and away from interaction with it). A theoretical two-point model was proposed to confirm experimental data, which showed poor conductivity of the CNT film as grown but has slight improvement after 40 min treatment.

Inkjet printing of paracetamol and indomethacin using electromagnetic technology: Rheological compatibility and polymorphic selectivity.

Drop-on-demand inkjet printing is a potential enabling technology both for continuous manufacturing of pharmaceuticals and for personalized medicine, but its use is often restricted to low-viscosity solutions and nano-suspensions. In the present study, a robust electromagnetic (valvejet) inkjet technology has been successfully applied to deposit prototype dosage forms from solutions with a wide range of viscosities, and from suspensions with particle sizes exceeding 2 µm. A detailed solid-state study of paracetamol, printed from a solution ink on hydroxypropyl methylcellulose (HPMC), revealed that the morphology of the substrate and its chemical interactions can have a considerable influence on polymorphic selectivity. Paracetamol ink crystallized exclusively into form II when printed on a smooth polyethylene terephthalate substrate, and exclusively into form I when in sufficient proximity to the rough surface of the HPMC substrate to be influenced by confinement in pores and chemical interactions. The relative standard deviation in the strength of the dosage forms was <4% in all cases, for doses as low as 0.8 mg, demonstrating the accuracy and reproducibility associated with electromagnetic inkjet technology. Good adhesion of indomethacin on HPMC was achieved using a suspension ink with hydroxypropyl cellulose, but not on an alternative polyethylene terephthalate substrate, emphasising the need to tailor the binder to the substrate. Future work will focus on lower-dose drugs, for which dosing flexibility and fixed dose combinations are of particular interest.

Microwave characterization of nanostructured ferroelectric Ba(0.6)Sr(0.4)TiO(3) thin films fabricated by pulsed laser deposition.

A series of nanostructured ferroelectric thin films of barium strontium titanate were fabricated using a pulsed laser deposition system with real-time in situ process control. Pulsed laser deposition parameters were controlled during the growth of nanostructured thin films for use in the development of high frequency tunable microwave devices. The thin films were all grown at the same substrate temperature and laser beam energy density, but the chamber oxygen partial pressure (COPP) was varied systematically from 19 mTorr through 1000 Torr. Structural and electromagnetic characterization was performed using atomic force microscopy and evanescent microwave microscopy, respectively. Atomic force microscopy showed a linear increase in grain size with increases in the ambient oxygen pressure from 38 to 150 mTorr and from 300 mTorr to 1000 Torr. The correlation of the microwave properties with the epitaxial film microstructure can be attributed to stresses and polarizability in the film. Microwave characterization showed that a COPP of 75 mTorr yielded the most desirable film in terms of tunability and loss tangent over a wide frequency range.