A tuning fork based wide range mechanical characterization tool with nanorobotic manipulators inside a scanning electron microscope

This study proposes a tuning fork probe based nanomanipulation robotic system for mechanical characterization of ultraflexible nanostructures under scanning electron microscope. The force gradient is measured via the frequency modulation of a quartz tuning fork and two nanomanipulators are used for manipulation of the nanostructures. Two techniques are proposed for attaching the nanostructure to the tip of the tuning fork probe. The first technique involves gluing the nanostructure for full range characterization whereas the second technique uses van der Waals and electrostatic forces in order to avoid destroying the nanostructure. Helical nanobelts (HNB) are proposed for the demonstration of the setup. The nonlinear stiffness behavior of HNBs during their full range tensile studies is clearly revealed for the first time. Using the first technique, this was between 0.009 N/m for rest position and 0.297 N/m before breaking of the HNB with a resolution of 0.0031 N/m. For the second experiment, this was between 0.014 N/m for rest position and 0.378 N/m before detaching of the HNB with a resolution of 0.0006 N/m. This shows the wide range sensing of the system for potential applications in mechanical property characterization of ultraflexible nanostructures.     

3D‐Printed Silicone Materials with Hydrogen Getter Capability

Organic getters are used to reduce the amount of reactive hydrogen in applications such as nuclear plants and transuranic waste. The present study examines the performance of getter loaded silicone elastomers in reducing reactive hydrogen gas from the gas phase and their capability of being 3D printed using direct ink writing techniques. The samples are placed in closed vessels and exposed to hydrogen atmosphere at pressures of 580 torr and 750 mtorr and at a temperature of 25 °C. The hydrogen consumption is measured as a function of time and normalized to getter concentration in the polymer. The performance of the getter‐loaded silicone elastomer containing 1,4‐bis[phenylethynyl]benzene (DEB) as the organic getter and Pd/C catalyst (ratio of 3:1 DEB to catalyst) decreases with increasing the resin's curing temperature. Chemical analysis suggests that DEB reacts with the silicone resin at high temperatures. In addition, it is demonstrated that the increased surface area of 3D printed composites results in improved getter performance.     

Synthesis and characterization of novel pH‐sensitive chitosan‐poly(acrylamide‐co‐itaconic acid) hydrogels

Novel pH‐sensitive chitosan‐poly(acrylamide‐co‐itaconic acid) hydrogels were prepared by free radical copolymerization of acrylamide and itaconic acid (IA) in chitosan solution. The hydrogels were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and the swelling ratios of the hydrogels in water (pH 6.8) and pH 1.2. The influence of composition on the thermal properties of the hydrogels was assessed. The glass transition temperatures of the samples increased with IA content, ranging from 110 to 136 °C. Swelling of the hydrogels was found to obey second‐order kinetics with respect to the remnant swelling, indicating that diffusion is controlled by the relaxation of chains. The equilibrium swelling degree was strongly dependent on pH and composition. At both pH values the highest water uptake was obtained for the IA‐free sample M1. From the equilibrium swelling results the average molar mass between crosslinks, M_c, and the crosslink density of the chitosan‐poly(acrylamide‐co‐itaconic acid) samples were calculated. The results evidenced the reinforcing effect of IA on the hydrogel structure. It is concluded that these highly swellable pH‐sensitive hydrogels can be useful for applications in biomedicine and pharmacy. © 2013 Society of Chemical Industry     

Batch cooling crystallization of xylitol produced by biotechnological route

BACKGROUND: This work deals with the xylitol production by biotechnological routes emphasizing the purification process using crystallization. RESULTS: Xylitol volumetric productivity of 0.665 g L^?1 h^?1 and yield of 0.7024 g g^?1 were obtained after 92 h fermentation. The fermented broth (61.3 g L^?1 xylitol) was centrifuged, treated and concentrated obtain a syrup (745.3 g L^?1 xylitol) which was crystallized twice, xylitol crystals with 98.5–99.2% purity being obtained. CONCLUSION: The hypothetical distribution obtained permits the determination of modeling parameters, which make possible the estimation of crystal dominant size from different initial experimental conditions. Copyright © 2008 Society of Chemical Industry     

Synthesis of an oxetane‐functionalized hemispiroorthocarbonate used as a low‐shrinkage additive in the cationic ultraviolet curing of oxetane monomers

The synthesis of an hemispiroorthocarbonate functionalized with an oxetane group is reported. The obtained monomer was used as a slow shrinkable additive in the cationic ultraviolet curing of a commercially available dioxetane resin. We evidenced polymer network flexibilization by increasing the oxetane‐functionalized hemispiroorthocarbonate content in the photocurable formulation. It was demonstrated that spiroorthocarbonate acted as a shrinkage reduction additive and reached expansion on volume after polymerization in the presence of 50 wt % of the functionalized spiroorthocarbonate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A kinetic study of the acceleration effect of substituted benzyl alcohols on the cationic photopolymerization rate of epoxidized natural oils

The rate of the cationic photopolymerization of epoxidized natural oils was enhanced by the addition of several mono, di and trisubstituted benzyl alcohols. The epoxidation of vegetable oils was achieved by using 30% hydrogen peroxide with methyl trioxo rhenium (MTO) as a phase transfer catalyst. Then, the effect of different methoxy-substituted benzyl alcohols on the curing rate was evaluated, using the real-time FT-IR technique. The overall result was an increase in the curing rate. The acceleration effect was explained on the basis of synergistic effects of two mechanisms, namely, the radical induced cationic photopolymerization and the activated monomer mechanism. Epoxidized oils with 2,5-dimethoxybenzyl alcohol as an accelerator exhibited the highest photopolymerization rate. Higher conversions were obtained using electron-transfer photosensitizers.     

Solving the forward kinematics problem in parallel robots using Support Vector Regression

The Stewart platform, a representative of the class of parallel manipulators, has been successfully used in a wide variety of fields and industries, from medicine to automotive. Parallel robots have key benefits over serial structures regarding stability and positioning capability. At the same time, they present challenges and open problems which need to be addressed in order to take full advantage of their utility. In this paper, we propose a new approach for solving one of these key aspects: the solution to the forward kinematics in real-time, an under-defined problem with a high-degree nonlinear formulation, using a popular machine learning method for classification and regression, the Support Vector Machines. Instead of solving a numerical problem, the proposed method involves applying Support Vector Regression to model the behavior of a platform in a given region or partition of the pose space. It consists of two phases, an off-line preprocessing step and a fast on-line evaluation phase. The experiments made have yielded a good approximation to the analytical solution, and have shown its suitability for real-time application.     

Synthesis of novel highly reactive silicone-epoxy monomers for cationic photopolymerizations

A series of novel cationically photopolymerizable silicone-epoxide monomers bearing substituted benzyl ether groups were prepared. Monomers with methoxy groups on the aromatic ring of the benzyl ether group were synthesized by sequential hydrosylation reactions of 1,1,3,3-tetramethyl disiloxane. Kinetic studies using real-time infrared spectroscopy of the cationic photopolymerizations of these novel monomers showed that those monomers with methoxy groups exhibited elevated rates of photopolymerization. The acceleration effect was explained on the basis of synergistic effects of two mechanisms, namely, the normal ring opening polymerization catalyzed by a Brönstead acid, and the cationic photopolymerization induced by the redox interaction between the free radicals formed in the backbone of the monomer and the onium salt used as photoinitiator. The methoxy groups on the aromatic ring of the benzyl ether enhance the stabilization of the carbocation formed in the structure of the monomer. Silicone-epoxy monomer with 2,5-dimethoxybenzyl ether group exhibited the higher photopolymerization rate. The latter compound can also be used as accelerator of the cationic photopolymerization of commercial silicone-epoxy monomer when used in low concentrations.     

Embedded Haptic Device Implementation for Soft Tissue Rendering

International Journal of Control, Automation and Systems - In this work, a haptic robotic device and its real-time virtual reality interface, deployed in an embedded computational platform is...