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Fine nanoapatite relics were deposited on glass substrates by electrohydrodynamic atomisation, using nanohydroxyapatite (nHA), nano-carbonated hydroxyapatite (nCHA) and nanosilicon- substituted hydroxyapatite (nSiHA) suspensions. These electrosprayed nanoapatites were evaluated in-vitro using simulated body fluid (SBF) and human osteoblast (HOB) cells. The SBF study revealed that newly-formed apatite layers were observed on the surface of the relics. Furthermore, enhanced HOB cell growth was observed on each of the nanoapatites at all time points. Hence, this work demonstrated that electrosprayed nanoapatites offer considerable potential as biomaterials.

A titanium dioxide precursor sol flowing through a needle at a flow rate of 10-10 m3 s-1 was subjected to an electric field of 4.5 kV to generate droplets in the size range 0.3–6 μm. The droplets were collected on a silicon substrate to form uniformly thick, dense films. Raman spectroscopy, X-ray diffraction, field emission scanning electron microscopy and UV/Vis spectroscopy were used to characterize as-deposited and annealed films. Raman spectra show the annealed films were anatase phase with annealing converting it to the rutile phase. The energy bandgap of the titanium dioxide film annealed to 500 °C shows an indirect bandgap energy of 3.50 eV and a direct bandgap energy of 3.95 eV.

The ability to create patterns of bioactive nanomaterials particularly on metallic and other types of implant surfaces is a crucial feature in influencing cell response, adhesion and growth. In this report, we uncover and elucidate a novel method that allows the easy deposition of a wide variety of predetermined topographical geometries of nanoparticles of a bioactive material on both metallic and non-metallic surfaces. Using different mesh sizes and geometries of a gold template, hydroxyapatite nanoparticles suspended in ethanol have been electrohydrodynamically sprayed on titanium and glass substrates under carefully designed electric field conditions. Thus, different topographies, e.g. hexagonal, line and square, from hydroxyapatite nanoparticles were created on these substrates. The thickness of the topography can be controlled by varying the spraying time.

An electrically charged jet of polymer solution is used to encapsulate silver particles contained in a suspension using co-axial dual needle jetting. The polymer solution flowing through the outer needle undergoes electrospinning while the silver suspension is simultaneously subjected to electrohydrodynamic atomization in the inner needle. The pattern and uniformity of encapsulation in the core is mainly determined by the speed of jetting in the inner needle. We demonstrate that this process could be utilized as a commercial freeform fabrication method of encapsulating metal particles within a polymeric sheath and this development could have numerous advanced technological applications.

In this paper, we uncover a new method for the preparation of biopolymer scaffolds and demonstrate its potential for the development of organs with the aid of tissue engineering. Two novel nanocomposite polymers, a nonbiodegradable polyhedral oligomeric silsesquioxane-poly (carbonate-urea)urethane and a biodegradable polyhedral oligomeric silsesquioxane-polycaprolactone-poly(carbonate-urea)urethane, have been subjected to flow in an electric field. Electrically forced microthreading of the polymers occurs and a three-dimensional print-patterning device was used to deposit fine (

Direct writing, consisting of the directed deposition of individual droplets of ceramic suspension using ink jet printing can be used to produce piezoelectric structures with feature sizes in excess of 100 μm. This work presents an alternative direct writing technique, consisting of directed individual droplets produced by electrohydrodynamic atomisation (EHDA), where feature sizes an order of magnitude smaller can be achieved. This technique opens up the possibility of using direct writing technology to produce integrated MEMS devices. Low toxicity lead zirconate titantate (PZT) sol has been used in conjunction with the EHDA process to produce isolated features and lines with dimensions as small as 20 μm. These features, when fired, form the perovskite PZT crystal structure. Using an X–Y stage to move the sample, it is possible to create a variety of structures.

Bioceramic fibres, scaffolds and mats are important structures in biomedical applications. Electrohydrodynamic routes are relatively new for processing advanced materials and in this paper we use electrospinning to prepare zirconia fibres diameter down to 200nm and hydroxyapatite (HA) fibres down to 1$m. Zirconia-polymer and nHA-polymer composite scaffolds structures (mats) with 400-1000 $m windows were also prepared.

This study utilises an electrohydrodynamic technique to prepare core-shell lipid nanoparticles with a tunable size and high active ingredient loading capacity, encapsulation efficiency and controlled release. Using stearic acid and ethylvanillin as model shell and active ingredients respectively, we identify the processing conditions and ratios of lipid:ethylvanillin required to form nanoparticles. Nanoparticles with a mean size ranging from 60 to 70 nm at the rate of 1.37 × 109 nanoparticles per minute were prepared with different lipid:ethylvanillin ratios. The polydispersity index was ≈ 21% and the encapsulation efficiency ≈ 70%. It was found that the rate of ethylvanillin release was a function of the nanoparticle size, and lipid:ethylvanillin ratio. The internal structure of the lipid nanoparticles was studied by transmission electron microscopy which confirmed that the ethylvanillin was encapsulated within a stearic acid shell. Fourier transform infrared spectroscopy analysis indicated that the ethylvanillin had not been affected. Extensive analysis of the release of ethylvanillin was performed using several existing models and a new diffusive release model incorporating a tanh function. The results were consistent with a core-shell structure.

Preparation of hydroxyapatite coated custom-made metallic bone-implants is very important for the replacement of injured bones of the body. Furthermore, these bone-implants are more stable under the corrosive environment of the body and biocompatible than bone-implants made up of pure metals and metal alloys. Herein, we describe a novel, simple and low-cost technique to prepare biocompatible hydroxyapatite coated titanium metal (TiM) implants through growth of self-formed TiO2 thin-layer (SFTL) on TiM via a heat treatment process. SFTL acts as a surface binder of HA nanoparticles in order to produce HA coated implants. Colloidal HA nanorods prepared by a novel surfactant-assisted synthesis method, have been coated on SFTL via atomized spray pyrolysis (ASP) technique. The corrosion behavior of the bare and surface-modified TiM (SMTiM) in a simulated body fluid (SBF) medium is also studied. The highest corrosion rate is found to be for the bare TiM plate, but the corrosion rate has been reduced with the heat-treatment of TiM due to the formation of SFTL. The lowest corrosion rate is recorded for the implant prepared by heat treatment of TiM at 700 °C. The HA-coating further assists in the passivation of the TiM in the SBF medium. Both SMTiM and HA coated SMTiM are noncytotoxic against osteoblast-like (HOS) cells and are in high-bioactivity. The overall production process of bone-implant described in this paper is in high economic value.

Cardiac tissue engineering (CTE) is currently a prime focus of research because of an enormous clinical need. In the present work, a novel functional material, poly(3-hydroxyoctanoate), P(3HO), a medium chain-length polyhydroxyalkanoate (PHA), produced using bacterial fermentation, was studied as a new potential material for CTE. Engineered constructs with improved mechanical properties, crucial for supporting the organ during new tissue regeneration, and enhanced surface topography, to allow efficient cell adhesion and proliferation, were fabricated. Results showed that the mechanical properties of the final patches were close to that of cardiac muscle. Biocompatibility of neat P(3HO) patches, assessed using neonatal ventricular rat myocytes (NVRM), showed that the polymer was as good as collagen in terms of cell viability, proliferation and adhesion. Enhanced cell adhesion and proliferation properties were observed when porous and fibrous structures were incorporated into the patches. In addition, no deleterious effect was observed on adult cardiomyocyte contraction when cardiomyocytes were seeded on the P(3HO) patches. Hence, P(3HO)-based multifunctional cardiac patches are promising constructs for efficient CTE. This work will have a positive impact on the development of P(3HO) and other PHAs as a novel new family of biodegradable functional materials with huge potential in a range of different biomedical applications, particularly CTE, leading to further interest and exploitation of these materials. Copyright © 2016 John WileySons, Ltd.

Nanofibrous systems are attracting increasing interest as a means of drug delivery, although a significant limitation to this approach has been manufacture on a scale commensurate with dosage form production. However, recent work has suggested that nanofibers may be successfully manufactured on a suitable scale using the novel process of pressurized gyration (PG). In this study, we explore the potential of PG as a novel means of generating amorphous solid dispersions of poorly water-soluble drugs with enhanced dissolution performance. We examine the effect of increasing drug loading on fiber properties including size, surface characteristics, and the physical state of both components. Dispersions of ibuprofen in poly(vinylpyrrolidone) (PVP) were prepared (up to 50% w/w loading) and characterized using a range of imaging, thermal, diffraction, and spectroscopic techniques, while the release profiles were studied using sink and non-sink (pH 1.0) conditions. The drug was found to be dispersed on a molecular basis within the fibers; attenuated total reflection FTIR indicated evidence for a direct interaction between the drug and polymer at lower drug loading by the identification of a strong single band in the carbonyl region and amide region of ibuprofen and PVP respectively. Dissolution studies under sink conditions indicated a substantial increase in release rate, while non-sink studies showed evidence for supersaturation. It is concluded that PG presents a viable method for the production of drug-loaded nanofibers for oral administration with enhanced in vitro dissolution rate enhancement.

In this work, the biosensing and antibacterial capabilities of PVA-lysozyme microbubbles have been explored. Gas-filled PVA-lysozyme microbubbles with and without gold nanoparticles in the diameter range of 10 to 250 μm were produced using a single-step pressurized gyration process. Fluorescence microscopy showed the integration of gold nanoparticles on the shell of the microbubbles. Microbubbles prepared with gold nanoparticles showed greater optical extinction values than those without gold nanoparticles, and these values increased with the concentration of the gold nanoparticles. Both types of microbubbles showed antibacterial activity against Gram-negative Escherichia coli (E. coli), with the bubbles containing the gold nanoparticles performing better than the former. The conjugation of the microbubbles with alkaline phosphatase allowed the detection of pesticide paraoxon in aqueous solution, and this demonstrates the biosensing capabilities of these microbubbles.

Ptosis describes a low position of the upper eyelid. When this condition is due to poor function of the levator palpebrae superioris muscle, responsible for raising the lid, "brow-suspension" ptosis correction is usually performed, which involves internally attaching the malpositioned eyelid to the forehead musculature using brow-suspension materials. In service, such materials are exposed to both rapid tensile loading and unloading sequences during blinking, and a more sustained tensile strain during extended periods of closure. In this study, various mechanical tests were conducted to characterise and compare some of commonly-used synthetic brow-suspension materials (Prolene(®), Supramid Extra(®) II, Silicone rods (Visitec(®) Seiff frontalis suspension set) and Mersilene(®) mesh) for their time-dependent response. At a given constant tensile strain or load, all of the brow-suspension materials exhibited stress-relaxation or creep, with Prolene(®) having a statistically different relaxation or creep ratio as compared with those of others. Uniaxial tensile cyclic tests through preconditioning and fatigue tests demonstrated drastically different time-dependent response amongst the various materials. Although the tests generated hysteresis force-strain loops for all materials, the mechanical properties such as the number of cycles required to reach the steady-state, the reduction in the peak force, and the cyclic energy dissipation varied considerably. To reach the steady-state, Prolene(®) and the silicone rod required the greatest and the least number of cycles, respectively. Furthermore, the fatigue tests at physiologically relevant conditions (15% strain controlled at 6.5 Hz) demonstrated that the reduction in the peak force during 100,000 cycles ranged from 15% to 58%, with Prolene(®) and the silicone rod exhibiting the greatest and the least value, respectively. Many factors need to be considered to select the most suitable brow-suspension material for ptosis correction. These novel data on the mechanical time-dependent performance could therefore help to guide clinicians in their decision-making process for optimal surgical outcome.

Two monodisperse nano-suspensions, which contain 20-nm and 120-nm silica particles (30 wt.%), were electrohydrodynamically jetted simultaneously in coaxial needles. Irrespective of which suspension was in the inner or outer needle, the cone-jet mode was obtained and the droplets resulting from jet break-up were used to direct write ∼80 µm lines. Turbulent flow in the cones ensured that the suspensions were subjected to intense mixing and therefore the microstructure contains a random mixture of the two types of nanoparticles of unchanged morphology.

Hydroxyapatite nano-particles have been synthesised by a precipitation reaction. These particles were then incorporated in a suspension containing ethanol as the liquid carrier. The suspension was subjected to flow in an electric field to generate a jet and, subsequently, droplets, which were deposited according to pre-determined topographies using a printing device. Thus, several nHA topographies have been generated and investigated using optical and scanning electron microscopy. In particular, nHA tracks down to 50 mu m in width have been prepared and this forming route offers the creation of nHA topographies to a high resolution not achieved by print-deposition techniques before.

Fabricating artificial vascularised tissue would involve tissue-engineering techniques, but current technology limits this as cultured cells depend on growth media in vitro and on diffusion in vivo. Therefore, there is a need to construct a synthetic microvascular network, which would sustain these cultured cells in a similar manner to normal tissue. This is again hampered by the poor patency rates of current microvascular grafts. Based on our previous work on polyhedral oligomeric silsesquioxane-polyurethane nanocomposites, which have shown the unique ability to repel coagulant proteins whilst still allowing endothelialisation, we have now developed a new generation of microvascular prosthesis using this polymer. Using these dip-coated nanocomposite microvessels, we have shown that it is possible to mimic the hydraulic conductivity and pressure-responsive radial compliance characteristics of biological microvessels. This would allow nutrient exchange across its walls as well as minimise compliance mismatch throughout the physiological pressure range thus reducing intimal hyperplasia in the long term. This microvessel would have the following implications: (1) as a microvascular substitute to vein grafts and (2) in the future as a component of a microvascular network.

A dispersion containing 15nm gold particles in ethanol was subjected to electrohydrodynamic atomization, producing droplets with an average size of ≈26μm as measured by laser diffraction. An electrohydrodynamic direct-write device was used to deposit the dispersion onto silicon wafers with the intention of printing gold tracks. Immediately after deposition ethanol evaporated, leaving the gold particles organised in a ≈75μm wide central region surrounded by two regions, each ≈50μm wide, at the edge of which two further gold tracks, each ≈7μm existed.

The behaviour of three high viscosity (4875, 12 125 and 58 560 mPa s), dielectric liquids was investigated at flow rates of 10 −10 , 10 −12 and 10 −14 m 3 s −1 and the applied voltage range 6–15 kV. In these experiments, due to the low electrical conductivity of the liquids (10 −13 S m −1 ) and therefore the ensuing high electrical relaxation time, classical electrohydrodynamic atomization conditions are not satisfied. Only dripping and unstable jetting were observed at 4875 mPa s. A transition from no jetting to stable microthreading was observed for the 12 125 and 58 560 mPa s samples. The relics accompanying the transition were found to change from discrete droplets to a continuous filament. Stable microthreading, which generates uniform filaments, was obtained for the 12 125 mPa s sample at flow rates 10 −10 and 10 −12 m 3 s −1 and in the case of the 58 560 mPa s sample at all the flow rates investigated. The high viscosity assisted stable microthreading with the filament diameter decreasing with increasing applied voltage and more dramatically decreasing with reducing flow rate.

A zirconia suspension containing 5–10 nm size zirconia particles was modified by adding different amounts of polymer solution to enable electrospinning of zirconia fibers from a range of compositions. The electrospun fibers were heat treated at 600° and 1200°C, and analysis of size distribution reveals that zirconia fibers down to about 200 nm in diameter can be prepared in this way, in contrast to other spinning processes, which are able to produce zirconia fibers having diameters ≥3000 nm.

Nano-sized HA (nHA) was applied to the surface of glass and titanium substrates using electrostatic atomisation spray (EAS) deposition. The phase purity of nHA was confirmed by X-ray diffraction. The nHA suspension consisted of rod–like particles 20-30nm in width and 50-100nm in length. The viscosity and conductivity of nHA suspension were 321 mPa s and 5.6 x 10-4 S/m, respectively. EAS of nHA in cone-jet mode was achieved at flow rate of 10-9 m3s-1 with the applied voltage between the needle and the ring-shaped ground electrode of ~6 kV. Micrometer- to submicrometerscaled nHA islands were successfully deposited on the substrate surface. Image analysis showed that the area percentage of nHA increased with deposition time, it covered 50% of the surface area after 10s of spraying. Partial dissolution of nHA was observed after immersion in deionised water for 1 month, particularly on the submicrometer sized nHA islands. Formation of a bone-like apatite layer was found after incubation in simulated body fluid (SBF K9) for 5 days, indicating the high bioactivity of the nHA deposits. In vitro culture with human osteoblast cells showed that the nHA islands were able to support the growth of HOB cells during 7 days of culture; the HOB cell activity increased with culture time as well as EAS deposition time. Immunofluorescence study showed that HOB cells expressed well-organised actin stress fibres on nHA deposited surfaces after 3 days of culture. The result indicated that nHA deposition provided more favourable surfaces for cell attachment. Therefore, electrostatic atomization spray deposition of nHA offers great potential for the creation of bioactive surfaces on bioinert implant surface to provide improved interfacial bonding with host tissues.

A novel process, namely replication combined with electrospraying, was used to fabricate bioceramic (zirconia) scaffolds with the intention of improving the mechanical function of hard tissue engineering scaffolds. A comparative study was carried out on the microstructure and mechanical properties of zirconia foams prepared by this new process or by the conventional slurry-dip coating method. After forming the green bodies, they were subjected to a sintering heat treatment at 1450°C for 5 h. It was found that the number and size of microcracks and micropores can be reduced in foams prepared by electrospraying in comparison with those prepared by slurry-dip coating. The values of compressive mechanical strength and Young's modulus were found to be collectively higher for scaffolds prepared by electrospraying than for those prepared by slurry-dip coating. Moreover, the mechanical reliability was improved in foams produced by the electrospraying technique. The improvement is attributable to the reduction in the population and size of microcracks and micropores.

Microspheres are potential candidates for the protein drug delivery. In this work, we prepared polymer-coated starch/bovine serum albumin (BSA) microspheres using co-axial electrohydrodynamic atomization (CEHDA). First, starch solution in dimethyl sulphoxide (DMSO) was prepared and then an aqueous solution of BSA was added to it to make a starch–BSA solution. Subsequently, this solution was made to flow through the inner capillary, while the polymer, polydimethylsiloxane (PDMS), flowed through the outer capillary. On collection, filtration and subsequent drying, near-monodisperse microspheres of 5–6 μm in size were obtained. The microspheres were characterized by Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy. Cumulative BSA release was investigated by UV spectroscopy. BSA structure and activity was preserved in the microspheres and its release in 0.01 M phosphate buffered saline (PBS) was studied over a period of 8 days. There was an initial burst with 32 wt% of total BSA released in 2 h. Overall 75 wt% of BSA was released over a 7 day period.

In this work, maize starch was used to demonstrate a novel method which enables the preparation of starch films and coatings with good thickness control. 5% starch in de-ionized water (w/v) was gelatinized at 120 °C for 30 min, subsequently small quantities of dispersant and ethanol were added and subjected to ultrasonic disruption to make a stable modified starch solution. Electrohydrodynamic behavior of this solution was studied and optimum conditions for film preparation were determined. The solution was then electrosprayed in the cone-jet mode and films were collected on a rotating plate. Film thickness was investigated by electron microscopy. Films of varying thickness were prepared by varying the electrospraying time and their characteristics are compared with solvent-cast films.

In this work we demonstrate a novel method of preparing composite ceramic microstructures, using alumina–zirconia as an example. Suspensions of these two ceramics, containing a similar solids content, were simultaneously subjected to electrohydrodynamic atomization (EHDA) in the stable cone-jet mode and the resulting relics were analyzed by microscopical techniques before and after partial sintering at 1200°C. We show that the new method, coaxial EHDA (CEHDA), is capable of forming different annular microstructures, which are mainly controlled by the speed of the jetting.

The deposition of a propanol-based lead zirconate titanate (PZT) sol using electrohydrodynamic atomization (EHDA) in the stable cone-jet mode was investigated. The droplets generated were deposited onto a copper substrate as a film, which was investigated using X-ray diffraction and scanning electron microscopy. The PZT film was shown to contain uniform nano-particles of PZT, which maintained their shape on sintering (650 degrees C, 1 hour) while forming the perovskite phase of PZT.

This paper reports jet break-up phenomena, which occurs during the electrohydrodynamic atomization (EHDA) of nano-suspensions. We investigated three ethylene glycol-based near-monodisperse suspensions, containing 30 wt% of SiO2 particles sized at 20, 80 and 120 nm. These suspensions were subjected to electrohydrodynamic atomization in the stable cone-jet mode and the jet break-up in each is discussed and compared with those of liquids reported in the literature.

In this paper we report a breakthrough in accurately print-patterning features from a nano-suspension. Twenty nanometer size equiaxed silica particles dispersed in a liquid medium were subjected to electrohydrodynamic forces and the type of jetting observed was mapped over a pico to femto flow rate regime-electric field parametric space. In the stable cone-jet mode, ∼60 μm features are patterned using a unique but simple, computer-controlled device. By reducing the flow rate by a further three orders of magnitude, a fine jet can be generated instantaneously and we are able to exploit this and accurately position ∼13 μm diameter equiv-spaced droplet-relics, which contain a dense assembly of the nanoparticles. We also demonstrate drawing of ∼17 μm wide lines of the nano-suspension.

A general equation applicable to a sphere, an infinite plate, and an infinite cylinder is used to calculate the transient diffusion of degradation product in a ceramic molding during pyrolysis. The solution includes the concentration-dependent diffusion coefficient for diffusion of monomer in its parent polymer which forms the continuous phase in the ceramic in the as-molded state. In the early stages of pyrolysis, before continuous porosity has developed, the model searches for the critical heating rate above which defects are produced. Reasonable agreement is obtained with experimentally measured critical heating rates for 3-mm-thick plates.

Electrospraying of nano-sized hydroxyapatite (HA) has been used as a technique to modify the surface of alumina in order to achieve the goal of improving bone integration. A porous HA coating on alumina was produced by heat treating electrsprayed HA. Preliminary in vitro studies shown that this porous HA coating provided a favourable surface for attachment and growth of HOB cells. The results indicate that electrospraying is a very promising technique to create thin HA coatings on a range of biomedical implants to improve interfacial bonding with the host tissue.

A suspension containing 20-nm-size inorganic particles was subjected to electrohydrodynamic atomization (EHDA) in the stable cone-jet mode. The droplet sizes generated were measured using laser diffraction. These results are compared to the stable cone-jet mode of atomization of a suspension containing 500-nm particles in the same liquid medium. Significant differences in the droplet size distributions were observed. The nano-suspension showed a tri-modal distribution while the micro-suspension was near-monodisperse.

A ceramic ink that contains 30 vol% of zirconia in butyl acetate and 2 wt% of a commercial oligomeric dispersant is considered. The dispersion and viscosity of this ink was optimized in previous work; however, its conductivity is too low for continuous ink-jet printing. The conductivity has been improved by the addition of ethanol and ammonium nitrate, but this addition detrimentally affects the dispersion, viscosity, and surface tension of the ink. This problem has been largely overcome by reducing the amount of ceramic in the ink. The ceramic inks that have been developed are tested in a pressurized, continuous ink-jet printer, and, depending on their performance, the ink composition is modified further.

Different amounts (0.5-10.0 wt%) of an oligomeric dispersant were added to a ceramic ink containing 30 vol% of zirconia in butyl acetate, The sediment packing densities of the resulting suspensions were measured. The viscosities of the suspensions were determined using a syringe that was adapted as a capillary viscometer suitable for the measurement of the low viscosities encountered (up to 400 mPa . s). The highest sediment-packing density coincided with the lowest viscosity and occurred when 1-2 wt% of dispersant, based on the ceramic, was added. Investigation of the supernatant of the suspensions by thermogravimetric analysis indicated that this amount corresponded to the highest level of adsorption of the dispersant on the ceramic. The sediment from this suspension yielded a high density on subsequent sintering.

This paper describes the preparation of ceramic inks for forming ceramic components by multilayer printing using a continuous-ink-jet printer. The selection of appropriate binders and dispersants combined with high shear and ultrasonic mixing has enabled zirconia-containing inks to be printed successfully to produce 2.5 mm thick bars. Printing trials show that the method of dispersion of the ceramic powder in the ink is decisive for accurate ink droplet positioning. The quality of the vertical walls and the top surface of the bars are related closely to the rate of drying of each printed layer. Inks with higher ceramic volume loadings (up to 10%) were also studied and produced useful information for further investigations.

A suspension containing 20?nm silica particles in ethylene glycol was subjected to electrohydrodynamic atomization (EHDA) in the stable cone-jet mode using a ring-shaped ground electrode. The droplets produced were sized by laser diffraction and were in the range 0.5?20??m. Immediately after deposition, droplet relics were analysed by optical microscopy and were found to be in the size range 1?80??m. Subsequently, using a pointed rod-electrode (rather than a ring), and by increasing the intensity of the electric field and by reducing the flow rate of suspension subjected to EHDA, relics of in size were deposited using a patterning device. In both of the above instances, the relics contained two distinct zones, an outer ring of ethylene glycol and a much smaller dense inner region of silica nanoparticles. These results show that, by using EHDA, a novel controlled deposition method of nanosuspensions has been developed.

An alumina suspension, containing ∼20 vol.% of powder was pumped through a needle held at a high voltage, with respect to a point-like ground electrode, and subjected to electrostatic atomisation. The flow rate and voltage was varied between 10−9 and 10−8 m3 s−1, and 5 and 12 kV, respectively and the mode of atomisation observed was recorded to construct mode selection (M-S) maps. In the stable cone-jet mode, the jet diameter was measured as a function of flow rate and applied voltage. Alumina relics obtained in the stable cone-jet mode regime were collected and studied by optical microscopy to establish the conditions which generated the finest relics.

Nano-sized, rod-like hydroxyapatite (nHA) crystals were produced and shown to be phasepure by X-ray diffraction analysis, as no secondary phases were observed. The nHA suspension was electrosprayed onto glass substrates using a novel processing routine to maintain nanocrystals of hydroxyapatite. The biocompatibility of nHAwas determined using human monocyte-derived macrophages and human osteoblast-like (HOB) cell models. The release of lactate dehydrogenase (LDH) from human monocyte-derived macrophages was measured as an indicator of cytotoxicity. The release of the inflammatory cytokine, tumour necrosis factor alpha (TNF-alpha) from cells in the presence of nHA crystallites was used as a measure of the inflammatory response. Although there was some evidence of LDH release from human monocyte-derived macrophages when in contact with high concentrations of nHA crystals, there was no significant release of TNF-alpha. Moreover, nHA-sprayed substrates were able to support the attachment and the growth of HOB cells. These results indicate that nHA crystals may be suitable for intraosseous implantation and offers the potential to formulate enhanced composites for biomedical applications.

A polysilane with a C-to-Si ratio of 6.0 was pyrolysed to produce an amorphous matrix (source powder), which was heated further to obtain different products. These polysilane-derived samples were studied using X-ray diffraction, Raman spectroscopy, solid-state magic-angle-spinning nuclear magnetic resonance and transmission electron microscopy. The source powder is a hydrogenated matrix composed of free carbon, random SiC4 sites and trace SiCO species. Pyrolysis of the source powder leads to the nucleation and growth of SiC and progressive organization of free carbon. SiC forms at 1100°C and fast growth appears at 1700°C accompanied by obvious weight loss. SiC decomposition also occurs at high temperatures, which leads to the formation of relatively well-organized carbon. The structural evolution is discussed and compared with the literature.

A family of silicone oils, of similar density, surface tension, relative permittivity and electrical conductivity but having viscosities in the range 970– 58200 mPa s were used to elucidate the role of very high viscosity on the electrically driven flow of liquids. The electrical conductivities of the oils are very low (∼10 −9 mS m −1 ) and in effect the behaviour of these dielectric liquids is indicative of the viscosities and electrical conductivities encountered in the processing of concentrated suspensions containing inorganic powders. We show that these oils do not undergo electrostatic atomization in the applied voltage-flow rate regime we have investigated. Nevertheless, electrically forced stable jets are produced from some of the oils and in such instances the jet diameter, size of relics and droplets obtained have been estimated. We show that in the range 103– 10 4 mPa s , a stable ball cone jet prevails, however at >10 4 mPa s the liquids produce micro-threads.

Solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), X-ray diffraction (XRD), and scanning electron and transmission electron microscopy (SEM and TEM) are used to study thermal degradation of a Si−Al−C−O ceramic precursor in nitrogen. A polysilane (PS) and aluminum acetylacetonate (AlAce) in the weight ratio AlAce/PS = 2 were reacted to synthesize the precursor. Solid state 29Si and 27Al MAS NMR spectra of the precursor confirm the occurrence of chemical reactions between PS and AlAce during synthesis. A complete three-dimensional Si−O−Al network forms at 900 °C. Crystalline phases appear at 1300 °C, and the pyrolyzed product at 1700 °C is a solid solution of 2H−SiC and AlN. Solid state 29Si and 27Al MAS NMR and XRD provide detailed information about the phase formation and transformation. The morphological development and microstructure evolution are further characterized by SEM and TEM.

Over the past two decades it has been established that bone repair in the presence of implant materials can be optimized by control of their surface chemistry. Certain calcium phosphate materials are similar in composition to bone mineral and have been found to be osteoconductive [1–3]. These ceramic materials have therefore been developed as biomaterials for a range of different applications. However, although they promote direct bone apposition, their mechanical properties are relatively poor compared with other monolithic ceramics. Therefore, classes of applications have been developed to exploit the excellent biological properties of the materials while maintaining mechanically viable implants [4, 5]. There is now increasing evidence that surface topography both on the micro and nano-scale are important in determining the cell response to biomaterials [6– 11]. A number of studies have indicated that cell activity can be up-regulated through optimization of the surface properties of the substrate. Investigations originally concentrated on surface features of several tens of micrometers in scale, but more recently, evidence suggests that surface topography at a much finer scale may influence the cell response. Hydroxyapatite (HA) has been used in a number of different forms and several powder processing routes have been investigated in conjunction with HA [12– 18]. The application of jet-based suspension processing methods, such as ink-jet printing (IJP) [19, 20] and electrostatic atomization printing (EAP) [21, 22] allows solid freeforming of fine structures of advanced materials. In particular, EAP in the cone-jet mode enables the formation of

Several alumina suspensions were subjected to electrostatic atomisation at a constant applied voltage and constant flow rate. Various spray modes were observed and the sizes of droplets produced from each suspension were measured using laser diffraction. The sizes of relics obtained by depositing these droplets on a silicone release paper substrate were measured using optical microscopy. Using volume equivalence the relic sizes were used to calculate the size of the droplets, thus allowing a comparison with the laser diffraction results. The calculated and measured droplet distributions showed excellent agreement.

Solid freeforming is a genus of manufacturing processes in which three-dimensional objects are assembled by point, line or planar addition of material. Confining surfaces, such as mould or die walls, are absent. The shape is built by adding rather than subtracting material. Solid freeforming has come to be computer controlled over the past two decades in parallel with the expansion of the data handling capacity of personal computers. It can be used for rapid prototyping but also offers mass production pathways in which individuation is possible. It is of particular interest for the creation, inter alia, of prosthetics that can be individually built from modified X-ray computed tomographic data. Some routes offer the additional capability to control, from the computer, not just the shape but also the composition throughout a component. Thus, three-dimensional functional gradients in multiphase ordered composites become possible. The concept of 'design' now embraces the integration of the spatial va...

A polysilane (PS) has been modified chemically with aluminium acetylacetonate (AlAce) to prepare new Si‐Al‐C‐O precursors. Chemical reactions occur between PS and AlAce and this gives rise to higher pyrolysis yields from the precursors at 900°C in nitrogen, compared with that of PS, due to network formation by crosslinking. Further pyrolysis of the precursors to 1700°C in nitrogen produces ceramics of the SiC‐AlN system with composition dependent on the AlAce/PS ratio. The structures of the precursors and their pyrolysis products have been characterized and the influence of the AlAce/PS ratio has been elucidated.

This paper describes the methodology for simulating a reprographic ink with a ceramic ink based on a commercially available zirconia powder for direct ceramic ink-jet printing. Of over-riding importance was matching viscosity and this was tested systematically by using a mineral oil–hexane binary system. Of secondary importance was adjustment of the pressure defect behind the nozzle to compensate for small differences in surface tension. The inks tested in the wide array print-head were based on low electrical conductivity liquids to avoid damage to the electroding system. The organic binder for the zirconia ink was paraffin wax and the dispersant was a hydroxystearic acid based polyester.

Polymeric fibers are prepared by using electric field driven fiber production technology-electrospinning and pressure driven fiber production technology-pressurized gyration. Fibers of four different polymers: polyvinylidene fluoride (PVDF), poly(methyl methacrylate (PMMA), poly(N-isopropylacrylamide), and polyvinylpyridine (PVP), are spun by both techniques and differences are analyzed for their suitability as drug carriers. The diameters of electrospun fibers are larger in some cases (PVDF and PMMA), producing fibers with lower surface area. Pressurized gyration allows for a higher rate of fiber production. Additionally, drug-loaded PVP fibers are prepared by using two poorly water-soluble drugs (Amphotericin B and Itraconazole). In vitro dissolution studies show differences in release rate between the two types of fibers. Drug-loaded gyrospun fibers release the drugs faster within 15 min compared to the drug-loaded electrospun fibers. The findings suggest pressurized gyration is a promising and scalable approach to rapid fiber production for drug delivery when compared to electrospinning.

Water, glycerol and their mixtures having viscosities in the range 1– 1340 mPa s were subjected to electrostatic atomization at a constant applied voltage and flow rate. The conductivity of the liquids were kept approximately equal by adding citric acid and their density, relative permittivity and surface tension values were measured. The electrospray was deposited on silicone release paper and the size of the relics produced were measured. Results show that the increase in viscosity had a significant effect on the mode of atomization and increased the size and size distribution of relics obtained.

Ceramic ink droplets have been deposited on two fundamentally different types of substrate and the evolution of contact angle, width of the ink–substrate interface and droplet height was measured as a function of time from digital images of the droplet captured on video. On substrate type I, with a lower surface free energy than the surface tension of the ceramic ink, after reaching stability in a few seconds, the contact angle decreased and the width of the ink–substrate interface remained stationary. Subsequently, the contact angle stayed constant and thereafter reduced again, while the width of the ink–substrate interface decreased and remained constant thereafter. On substrate type II, with a higher surface free energy than the surface tension of the ceramic ink, stability was achieved instantaneously and the contact angle decreased rapidly, while the width of the ink–substrate interface increased initially but thereafter remained constant. The corresponding variation of droplet height due to spreading and evaporation, and volume shrinkage rate were also found to be much faster on the type–II substrate.

A novel computer-controlled method of depositing ceramic droplets, according to a pre-determined architecture is described. A 21 vol% alumina suspension flowing through a nozzle was subjected to electrostatic atomization in the cone-jet mode at different applied voltages. By using a point-like ground electrode the resulting spray was focused and printed on a substrate placed between the nozzle and the ground electrode. The substrate was moved with the aid of a 2-axis computer controlled stepper motor driven system which enabled the forming of different ceramic architectures. As an example, the word CERAMIC was printed. At an applied voltage of 10 kV, droplet relics in the print were in the size range 30–60 µm.