Electrohydrodynamic Atomization of a Concentrated Nano-Suspension

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.     

Novel method of preparing hydroxyapatite foams

Porous scaffolds are considered a key strategy in the concept of bone tissue engineering. Hydroxyapatite, which is a bioceramic has been used as a popular scaffold material due to its bioactive and osteoconductive properties. A combination of slurry-dipping and electrospraying has been used as a new foam fabrication method to produce porous and interconnected foam structures. The combined method has shown to overcome the shortcomings of the individual methods and it has produced open pores in the desired range of 100–350 μm. The porosity which was determined by calculation and microtomography was between 84% and 88%. Reduced cracks and thicker struts were observed in the microstructure, pointing to improved mechanical properties.     

Deposition of nano-hydroxyapatite particles utilising direct and transitional electrohydrodynamic processes

Electrohydrodynamic spraying is a well established process used to deposit, coat, analyse and synthesise materials within the biomedical remit. Recently, electrohydrodynamic printing has been developed to afford structures for potential applications in the biomedical and medical engineering fields. Both of these processes rely on the formation of an electrically-induced jet, however the resulting products can be made strikingly different and offer potential in broader applications. Here we show how spraying and printing are linked by elucidating the ease of transition between the processes. Changes in the deposition distance can result in either spray (>10 mm) or print formation (<3 mm), with an overlap of the two in between this range. For the optimal printing distance of 0.5 mm, gradual changes in the applied voltage (0-4.5 kV) encounters transitional printing modes (dripping, micro-dripping, rapid micro-dripping, unstable and stable jetting) which can be utilised for patterning. The results indicate the robustness of the electrohydrodynamic route in the nano-materials processing arena, with emphasis on biomedical materials.     

Calcium Alginate Foams Prepared by a Microfluidic T-Junction System: Stability and Food Applications

Highly porous alginate foams were prepared via a novel route in which highly viscous alginate solutions were bubbled using a microfluidic T-junction device. The relationship between bubble size and bubbling conditions such as air pressure and solution flow rate was studied, and the ability of the T-junction setup to generate monodisperse microbubbles (mean diameter, ～154 μm) and produce porous foams was systematically investigated. The foams were characterised by optical and scanning electron microscopy. Foams of varying lengths (12–45 mm) were successfully prepared using this technique, with an average density of ～235 kg/m³. The pore diameter within the foams was determined by microscopy to be in the range of 600 nm–200 μm with a mean diameter of ～31 μm. It was concluded that porosity in the foam (>90%) can be varied depending on the initial bubble size. Thus, a possible production method of stable highly porous solid foams for exploitation in food and bioprocess technologies is presented by which products can be made to different sizes.     

High-speed camera characterization of voluntary eye blinking kinematics

Blinking is vital to maintain the integrity of the ocular surface and its characteristics such as blink duration and speed can vary significantly, depending on the health of the eyes. The blink is so rapid that special techniques are required to characterize it. In this study, a high-speed camera was used to record and characterize voluntary blinking. The blinking motion of 25 healthy volunteers was recorded at 600 frames per second. Master curves for the palpebral aperture and blinking speed were constructed using palpebral aperture versus time data taken from the high-speed camera recordings, which show that one blink can be divided into four phases; closing, closed, early opening and late opening. Analysis of data from the high-speed camera images was used to calculate the palpebral aperture, peak blinking speed, average blinking speed and duration of voluntary blinking and compare it with data generated by other methods previously used to evaluate voluntary blinking. The advantages of the high-speed camera method over the others are discussed, thereby supporting the high potential usefulness of the method in clinical research.     

酿酒酵母发酵混合果汁的功能性研究

采用酿酒酵母Saccharomyces cerevisiae KD对苹果、猕猴桃、梨混合果汁进行发酵,研究了该混合果汁发酵过程中酿酒酵母对真菌毒素棒曲霉素的去除作用及其降解产物对大肠杆菌的毒性,并对其发酵过程中的抗氧化能力及对α-淀粉酶、脂肪酶的抑制效果进行分析。结果发现,混合果汁发酵过程中棒曲霉素的含量持续下降直至完全降解,且棒曲霉素的降解产物对大肠杆菌无毒害;对抗氧化能力指标进行检测,发现发酵果汁的DPPH·、ABTS+·清除率和还原力相比新鲜果汁分别提高了15.0%、45.9%和9.6%,抗氧化能力显著增强(P<0.05)。此外,混合发酵果汁可以有效地抑制与肥胖相关的α-淀粉酶、脂肪酶的活力,抑制率分别为52.4%和45.2%。本文的研究结果可为开发功能性发酵果汁提供科学依据和技术支持。     

Multiparameter mapping of polymer properties for fast thermolysis of powder moldings

Ceramic or metal injection molding involves the shaping of a crowded suspension of particles in a polymer that is later removed by thermolysis. During heating, degradation products dissolve in the parent polymer and diffuse to the free surfaces where evaporation occurs. If heated too rapidly in the initial stage, the solution at the center of the molding boils and a bubble forms. This article explores the implications of a multiparameter model that predicts the highest permissible heating rate in terms of polymer properties and maps the outcome. The aim is to develop criteria for the deliberate synthesis of thermally labile copolymers from a knowledge of the desirable property combinations. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 545–557, 1998     

Ink-jet printing of ceramic pillar arrays

A high performance 500 nozzle in-line piezoelectric drop-on-demand print-head mounted on a linear table with z-axis control was used to prepare arrays of fine ceramic pillars. Such structures may find applications in miniature heat exchangers, catalyst supports, for cell up-regulation in prosthetics or in polymer-ceramic piezoelectric 1–3 composites. The ink conveyed 14 vol% fine zirconia and deposited a wax-based suspension in an octane-alcohol mixture. The dried ink contained 63 vol% zirconia.