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Materials, Volume 5, Issue 12 (December 2012) – 31 articles , Pages 2439-3005

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1396 KiB  
Article
Comparison of Fatigue Properties and Fatigue Crack Growth Rates of Various Implantable Metals
by Yoshimitsu Okazaki
Materials 2012, 5(12), 2981-3005; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122981 - 19 Dec 2012
Cited by 39 | Viewed by 12388
Abstract
The fatigue strength, effects of a notch on the fatigue strength, and fatigue crack growth rate of Ti-15Zr-4Nb-4Ta alloy were compared with those of other implantable metals. Zr, Nb, and Ta are important alloying elements for Ti alloys for attaining superior long-term corrosion [...] Read more.
The fatigue strength, effects of a notch on the fatigue strength, and fatigue crack growth rate of Ti-15Zr-4Nb-4Ta alloy were compared with those of other implantable metals. Zr, Nb, and Ta are important alloying elements for Ti alloys for attaining superior long-term corrosion resistance and biocompatibility. The highly biocompatible Ti-15Zr-4Nb-4Ta alloy exhibited an excellent balance between strength and ductility. Its notched tensile strength was much higher than that of a smooth specimen. The strength of 20% cold-worked commercially pure (C.P.) grade 4 Ti was close to that of Ti alloy. The tension-to-tension fatigue strength of an annealed Ti-15Zr-4Nb-4Ta rod at 107 cycles was approximately 740 MPa. The fatigue strength of this alloy was much improved by aging treatment after solution treatment. The fatigue strengths of C.P. grade 4 Ti and stainless steel were markedly improved by 20% cold working. The fatigue strength of Co-Cr-Mo alloy was markedly increased by hot forging. The notch fatigue strengths of 20% cold-worked C.P. grade 4 Ti, and annealed and aged Ti-15Zr-4Nb-4Ta, and annealed Ti-6Al-4V alloys were less than those of the smooth specimens. The fatigue crack growth rate of Ti-15Zr-4Nb-4Ta was the same as that of Ti-6Al-4V. The fatigue crack growth rate in 0.9% NaCl was the same as that in air. Stainless steel and Co-Cr-Mo-Ni-Fe alloy had a larger stress-intensity factor range (ΔK) than Ti alloy. Full article
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305 KiB  
Review
Characterization of Nanocomposites by Thermal Analysis
by Carola Esposito Corcione and Mariaenrica Frigione
Materials 2012, 5(12), 2960-2980; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122960 - 19 Dec 2012
Cited by 176 | Viewed by 10463
Abstract
In materials research, the development of polymer nanocomposites (PN) is rapidly emerging as a multidisciplinary research field with results that could broaden the applications of polymers to many different industries. PN are polymer matrices (thermoplastics, thermosets or elastomers) that have been reinforced with [...] Read more.
In materials research, the development of polymer nanocomposites (PN) is rapidly emerging as a multidisciplinary research field with results that could broaden the applications of polymers to many different industries. PN are polymer matrices (thermoplastics, thermosets or elastomers) that have been reinforced with small quantities of nano-sized particles, preferably characterized by high aspect ratios, such as layered silicates and carbon nanotubes. Thermal analysis (TA) is a useful tool to investigate a wide variety of properties of polymers and it can be also applied to PN in order to gain further insight into their structure. This review illustrates the versatile applications of TA methods in the emerging field of polymer nanomaterial research, presenting some examples of applications of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA) and thermal mechanical analysis (TMA) for the characterization of nanocomposite materials. Full article
(This article belongs to the Special Issue Advances in Multifunctional Materials)
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1072 KiB  
Review
Recent Progress in Surface Modification of Polyvinyl Chloride
by Ahmad Asadinezhad, Marián Lehocký, Petr Sáha and Miran Mozetič
Materials 2012, 5(12), 2937-2959; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122937 - 18 Dec 2012
Cited by 80 | Viewed by 11396
Abstract
Surface modification of polymers has become a vibrant field of research on account of a myriad of rationales which stimulated numerous efforts. The current paper serves as a condensed survey of the advances made through different approaches adopted for tuning the surface properties [...] Read more.
Surface modification of polymers has become a vibrant field of research on account of a myriad of rationales which stimulated numerous efforts. The current paper serves as a condensed survey of the advances made through different approaches adopted for tuning the surface properties of polyvinyl chloride as a homopolymer extensively used on a large scale. Though it does not address all challenges involved, this paper communicates and highlights, through concise discussion, the findings of the efforts undertaken in recent decades. It is ultimately concluded with a perspective of the huge capacities and promising future directions. Full article
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2456 KiB  
Article
Dispersion of Pt Nanoparticle-Doped Reduced Graphene Oxide Using Aniline as a Stabilizer
by Ali Grinou, Young Soo Yun, Se Youn Cho, Hyun Ho Park and Hyoung-Joon Jin
Materials 2012, 5(12), 2927-2936; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122927 - 18 Dec 2012
Cited by 26 | Viewed by 6640
Abstract
In this study, a simple one-step method was developed to load small-sized Pt nanoparticles (3.1 ± 0.3 nm) in large quantities (50 wt %) on aniline-functionalized and reduced graphene oxide (r-fGO). In the process, an ethylene glycol solution and aniline-functionalized moiety play the [...] Read more.
In this study, a simple one-step method was developed to load small-sized Pt nanoparticles (3.1 ± 0.3 nm) in large quantities (50 wt %) on aniline-functionalized and reduced graphene oxide (r-fGO). In the process, an ethylene glycol solution and aniline-functionalized moiety play the roles of reducing agent and stabilizer for the Pt nanoparticles, respectively, without damaging the graphite structures of the r-fGO. The Pt nanoparticles loading on the surface of r-fGO with uniform dispersion have a great effect on the electrical conductivity. Full article
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839 KiB  
Article
Preparation, Characterization and Release of Urea from Wheat Gluten Electrospun Membranes
by Daniela Denisse Castro-Enríquez, Francisco Rodríguez-Félix, Benjamín Ramírez-Wong, Patricia Isabel Torres-Chávez, María Mónica Castillo-Ortega, Dora Evelia Rodríguez-Félix, Lorena Armenta-Villegas and Ana Irene Ledesma-Osuna
Materials 2012, 5(12), 2903-2916; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122903 - 18 Dec 2012
Cited by 71 | Viewed by 8192
Abstract
Homogeneous and thin porous membranes composed of oriented fibers were obtained from wheat gluten (WG) using the electrospinning technique. SEM micrographs showed an asymmetric structure and some porosity, which, in addition to a small thickness of 40 mm, are desirable characteristics for the [...] Read more.
Homogeneous and thin porous membranes composed of oriented fibers were obtained from wheat gluten (WG) using the electrospinning technique. SEM micrographs showed an asymmetric structure and some porosity, which, in addition to a small thickness of 40 mm, are desirable characteristics for the membranes’ potential application in release systems. The membranes were loaded with urea to obtain pastilles. FT-IR and DSC studies confirmed the existence of interactions via hydrogen bonding between urea and WG proteins. The pastilles were studied as prolonged-released systems of urea in water. The release of urea during the first 10 min was very fast; then, the rate of release decreased as it reached equilibrium at 300 min, with a total of »98% urea released. TGA analysis showed that the release system obtained is thermally stable up to a temperature of 117 °C. It was concluded that a prolonged-release system of urea could be satisfactorily produced using WG fibers obtained by electrospinning for potential application in agricultural crops. Full article
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1260 KiB  
Article
Optimization of the GaAs-on-Si Substrate for Microelectromechanical Systems (MEMS) Sensor Application
by Yunbo Shi, Hao Guo, Haiqiao Ni, Chenyang Xue, Zhichuan Niu, Jun Tang, Jun Liu, Wendong Zhang, Jifang He, Mifeng Li and Ying Yu
Materials 2012, 5(12), 2917-2926; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122917 - 17 Dec 2012
Cited by 14 | Viewed by 5555
Abstract
Resonant Tunneling Diodes (RTD) and High Electron Mobility Transistor (HEMT) based on GaAs, as the piezoresistive sensing element, exhibit extremely high sensitivity in the MEMS sensors based on GaAs. To further expand their applications to the fields of MEMS sensors based on Si, [...] Read more.
Resonant Tunneling Diodes (RTD) and High Electron Mobility Transistor (HEMT) based on GaAs, as the piezoresistive sensing element, exhibit extremely high sensitivity in the MEMS sensors based on GaAs. To further expand their applications to the fields of MEMS sensors based on Si, we have studied the optimization of the GaAs epitaxy layers on Si wafers. Matching superlattice and strain superlattice were used, and the surface defect density can be improved by two orders of magnitude. Combing with the Raman spectrum, the residual stress was characterized, and it can be concluded from the experimental results that the residual stress can be reduced by 50%, in comparison with the original substrate. This method gives us a solution to optimize the epitaxy GaAs layers on Si substrate, which will also optimize our future process of integration RTD and HEMT based on GaAs on Si substrate for the MEMS sensor applications. Full article
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1985 KiB  
Review
A Review: Fundamental Aspects of Silicate Mesoporous Materials
by Zeid A. ALOthman
Materials 2012, 5(12), 2874-2902; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122874 - 17 Dec 2012
Cited by 1384 | Viewed by 36199
Abstract
Silicate mesoporous materials have received widespread interest because of their potential applications as supports for catalysis, separation, selective adsorption, novel functional materials, and use as hosts to confine guest molecules, due to their extremely high surface areas combined with large and uniform pore [...] Read more.
Silicate mesoporous materials have received widespread interest because of their potential applications as supports for catalysis, separation, selective adsorption, novel functional materials, and use as hosts to confine guest molecules, due to their extremely high surface areas combined with large and uniform pore sizes. Over time a constant demand has developed for larger pores with well-defined pore structures. Silicate materials, with well-defined pore sizes of about 2.0–10.0 nm, surpass the pore-size constraint (<2.0 nm) of microporous zeolites. They also possess extremely high surface areas (>700 m2 g−1) and narrow pore size distributions. Instead of using small organic molecules as templating compounds, as in the case of zeolites, long chain surfactant molecules were employed as the structure-directing agent during the synthesis of these highly ordered materials. The structure, composition, and pore size of these materials can be tailored during synthesis by variation of the reactant stoichiometry, the nature of the surfactant molecule, the auxiliary chemicals, the reaction conditions, or by post-synthesis functionalization techniques. This review focuses mainly on a concise overview of silicate mesoporous materials together with their applications. Perusal of the review will enable researchers to obtain succinct information about microporous and mesoporous materials. Full article
(This article belongs to the Special Issue Advances in Mesoporous Materials)
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58 KiB  
Correction
Correction: Effect of AlF3 on the Density and Elastic Properties of Zinc Tellurite Glass Systems. Materials 2012, 5, 1361-1372.
by Haji Abdul Aziz Sidek, Shaharuddin Rosmawati, Mohamed Kamari Halimah, Khamirul Amin Matori and Zainal Abidin Talib
Materials 2012, 5(12), 2872-2873; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122872 - 13 Dec 2012
Viewed by 4020
Abstract
Due to an oversight, the data of the last column “Vs” in Table 1 was missing in the original version of this article [1]. [...] Full article
898 KiB  
Review
The Toxic Effects and Mechanisms of CuO and ZnO Nanoparticles
by Ya-Nan Chang, Mingyi Zhang, Lin Xia, Jun Zhang and Gengmei Xing
Materials 2012, 5(12), 2850-2871; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122850 - 13 Dec 2012
Cited by 611 | Viewed by 22887
Abstract
Recent nanotechnological advances suggest that metal oxide nanoparticles (NPs) have been expected to be used in various fields, ranging from catalysis and opto-electronic materials to sensors, environmental remediation, and biomedicine. However, the growing use of NPs has led to their release into environment [...] Read more.
Recent nanotechnological advances suggest that metal oxide nanoparticles (NPs) have been expected to be used in various fields, ranging from catalysis and opto-electronic materials to sensors, environmental remediation, and biomedicine. However, the growing use of NPs has led to their release into environment and the toxicity of metal oxide NPs on organisms has become a concern to both the public and scientists. Unfortunately, there are still widespread controversies and ambiguities with respect to the toxic effects and mechanisms of metal oxide NPs. Comprehensive understanding of their toxic effect is necessary to safely expand their use. In this review, we use CuO and ZnO NPs as examples to discuss how key factors such as size, surface characteristics, dissolution, and exposure routes mediate toxic effects, and we describe corresponding mechanisms, including oxidative stress, coordination effects and non-homeostasis effects. Full article
(This article belongs to the Special Issue Nanotoxicology)
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1330 KiB  
Article
Pulmonary Inflammation of Well-Dispersed Multi-Wall Carbon Nanotubes Following Intratracheal Instillation: Toxicity by Fiber of 1–5 µm in Length
by Masanori Horie, Mayumi Stowe, Tatsunori Kambara, Byeong Woo Lee, Shigehisa Endoh, Junko Maru, Takako Oyabu, Toshihiko Myojo, Akira Ogami, Kunio Uchida, Kazuhiro Yamamoto, Norihiro Kobayashi, Estushi Kuroda, Tetsuya Nakazato and Yasuo Morimoto
Materials 2012, 5(12), 2833-2849; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122833 - 13 Dec 2012
Cited by 5 | Viewed by 6275
Abstract
The pulmonary toxicity of multi-wall carbon nanotubes (MWCNT) were examined by intratracheal instillation. We prepared a well-dispersed MWCNT dispersion including MWCNTs of 3.71 µm geometric average length. The fiber length of most of the MWCNTs in the dispersion was 10 µm or less. [...] Read more.
The pulmonary toxicity of multi-wall carbon nanotubes (MWCNT) were examined by intratracheal instillation. We prepared a well-dispersed MWCNT dispersion including MWCNTs of 3.71 µm geometric average length. The fiber length of most of the MWCNTs in the dispersion was 10 µm or less. The MWCNT dispersion was administered to rat lung by single intratracheal instillation at doses of 0.2 mg and 0.6 mg/rat. Bronchoalveolar lavage fluid (BALF) was collected at 3 days, 1 week, 1 month, 3 months, and 6 months after instillation. The influences of the longer MWCNTs on the induction of inflammation and oxidative stress were examined by the number of neutrophils, cytokine induced neutrophil chemoattractant-1 (CINC-1), CINC-2, CINC-3 and HO-1 in the BALF. Additionally, ho-1 gene expression in the lung was examined. The intratracheal instillation of MWCNT induced transient inflammation dose dependently in the lung. The number of neutrophils was highest at 3 days after instillation and then decreased. However, the neutrophils in the MWCNT administered animals tended to be higher than in the control group until 3 months after instillation. The CINC-1 and CINC-2 concentrations in the BALF increased at 1 month after instillation. There were no significant differences in CINC-3 and HO-1 between the MWCNT administered animals and the control animals. These results revealed that the MWCNTs of 1–10 µm in length induced persistent inflammation in rat lung. There were no remarkable differences between the MWCNTs in the present study and previously reported, shorter MWCNTs prepared from “the same” raw MWCNT material. Full article
(This article belongs to the Special Issue Nanotoxicology)
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1563 KiB  
Article
Growth of High-Density Zinc Oxide Nanorods on Porous Silicon by Thermal Evaporation
by Nurul Izni Rusli, Masahiro Tanikawa, Mohamad Rusop Mahmood, Kanji Yasui and Abdul Manaf Hashim
Materials 2012, 5(12), 2817-2832; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122817 - 13 Dec 2012
Cited by 62 | Viewed by 10341
Abstract
The formation of high-density zinc oxide (ZnO) nanorods on porous silicon (PS) substrates at growth temperatures of 600–1000 °C by a simple thermal evaporation of zinc (Zn) powder in the presence of oxygen (O2) gas was systematically investigated. The high-density growth [...] Read more.
The formation of high-density zinc oxide (ZnO) nanorods on porous silicon (PS) substrates at growth temperatures of 600–1000 °C by a simple thermal evaporation of zinc (Zn) powder in the presence of oxygen (O2) gas was systematically investigated. The high-density growth of ZnO nanorods with (0002) orientation over a large area was attributed to the rough surface of PS, which provides appropriate planes to promote deposition of Zn or ZnOx seeds as nucleation sites for the subsequent growth of ZnO nanorods. The geometrical morphologies of ZnO nanorods are determined by the ZnOx seed structures, i.e., cluster or layer structures. The flower-like hexagonal-faceted ZnO nanorods grown at 600 °C seem to be generated from the sparsely distributed ZnOx nanoclusters. Vertically aligned hexagonal-faceted ZnO nanorods grown at 800 °C may be inferred from the formation of dense arrays of ZnOx clusters. The formation of disordered ZnO nanorods formed at 1000 °C may due to the formation of a ZnOx seed layer. The growth mechanism involved has been described by a combination of self-catalyzed vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism. The results suggest that for a more precise study on the growth of ZnO nanostructures involving the introduction of seeds, the initial seed structures must be taken into account given their significant effects. Full article
(This article belongs to the Special Issue Compound Semiconductor Materials)
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125 KiB  
Retraction
Retraction: Heidari, A.; Vedad, S.; Heidari, N.; Ghorbani, M. Flux Dynamics in Y358 Superconductors. Materials 2012, 5, 882-888.
by Shu-Kun Lin
Materials 2012, 5(12), 2816; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122816 - 12 Dec 2012
Cited by 1 | Viewed by 6269
Abstract
It has been brought to our attention by a reader of Materials that substantial portions of this article [1] have been translated from another publication [2] without credit. After confirming this to be the case with the authors, we have determined that indeed [...] Read more.
It has been brought to our attention by a reader of Materials that substantial portions of this article [1] have been translated from another publication [2] without credit. After confirming this to be the case with the authors, we have determined that indeed this manuscript clearly violates our policy of originality of all material submitted for publication and the generally accepted ethics of scientific publication. Consequently, the Editorial Team and Publisher have determined that it should be retracted. We apologize for any inconvenience this may cause. [...] Full article
3968 KiB  
Review
Holographic Gratings for Slow-Neutron Optics
by Juergen Klepp, Christian Pruner, Yasuo Tomita, Peter Geltenbort, Irena Drevenšek-Olenik, Saso Gyergyek, Joachim Kohlbrecher and Martin Fally
Materials 2012, 5(12), 2788-2815; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122788 - 12 Dec 2012
Cited by 25 | Viewed by 7087
Abstract
Recent progress in the development of holographic gratings for neutron-optics applications is reviewed. We summarize the properties of gratings recorded in deuterated (poly)methylmethacrylate, holographic polymer-dispersed liquid crystals and nanoparticle-polymer composites revealed by diffraction experiments with slow neutrons. Existing and anticipated neutron-optical instrumentations based [...] Read more.
Recent progress in the development of holographic gratings for neutron-optics applications is reviewed. We summarize the properties of gratings recorded in deuterated (poly)methylmethacrylate, holographic polymer-dispersed liquid crystals and nanoparticle-polymer composites revealed by diffraction experiments with slow neutrons. Existing and anticipated neutron-optical instrumentations based on holographic gratings are discussed. Full article
(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)
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1338 KiB  
Article
Topographical Anisotropy and Wetting of Ground Stainless Steel Surfaces
by Alfredo Calvimontes, Marc Mauermann and Cornelia Bellmann
Materials 2012, 5(12), 2773-2787; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122773 - 12 Dec 2012
Cited by 7 | Viewed by 5373
Abstract
Microscopic and physico-chemical methods were used for a comprehensive surface characterization of different mechanically modified stainless steel surfaces. The surfaces were analyzed using high-resolution confocal microscopy, resulting in detailed information about the topographic properties. In addition, static water contact angle measurements were carried [...] Read more.
Microscopic and physico-chemical methods were used for a comprehensive surface characterization of different mechanically modified stainless steel surfaces. The surfaces were analyzed using high-resolution confocal microscopy, resulting in detailed information about the topographic properties. In addition, static water contact angle measurements were carried out to characterize the surface heterogeneity of the samples. The effect of morphological anisotropy on water contact angle anisotropy was investigated. The correlation between topography and wetting was studied by means of a model of wetting proposed in the present work, that allows quantifying the air volume of the interface water drop-stainless steel surface. Full article
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902 KiB  
Article
An Ultrasensitive Electrochemical Immunosensor for Alpha-Fetoprotein Using an Envision Complex-Antibody Copolymer as a Sensitive Label
by Ping Xiong, Ning Gan, Yuting Cao, Futao Hu, Tianhua Li and Lei Zheng
Materials 2012, 5(12), 2757-2772; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122757 - 11 Dec 2012
Cited by 34 | Viewed by 6199
Abstract
A novel strategy is presented for sensitive detection of alfa-fetoprotein (AFP), using a horseradish peroxidase (HRP)-functionalized Envision antibody complex (EVC) as the label. The Envision-AFP signal antibody copolymer (EVC-AFP Ab2) was composed of a dextran amine skeleton anchoring more than 100 molecules of [...] Read more.
A novel strategy is presented for sensitive detection of alfa-fetoprotein (AFP), using a horseradish peroxidase (HRP)-functionalized Envision antibody complex (EVC) as the label. The Envision-AFP signal antibody copolymer (EVC-AFP Ab2) was composed of a dextran amine skeleton anchoring more than 100 molecules of HRP and 15 molecules of secondary antibody, and acted as a signal tag in the immunosensor. The sensor was constructed using the following steps: First, gold electrode (GE) was modified with nano-gold (AuNPs) by electro-deposition in HAuCl4 solution. The high affinity of the AuNPs surface facilitates direct formation of a self-assembled thiolated protein G layer. Next, the coated GE was incubated in a solution of AFP capture antibody (AFP Ab1); these antibodies attach to the thiolated protein G layer through their non-antigenic regions, leaving the antigen binding sites for binding of target analyte. Following a sandwich immunoreaction, an EVC-AFP Ab2-AFP-AFP Ab1 immunocomplex was formed on the electrode surface, allowing large amounts of HRP on the complex to produce an amplified electrocatalytic current of hydroquinone (HQ) in the presence of hydrogen peroxide (H2O2). Highly amplified detection was achieved, with a detection limit of 2 pg/mL and a linear range of 0.005–0.2 ng/mL for AFP in 10 μL undiluted serum; this is near or below the normal levels of most cancer biomarker proteins in human serum. Measurements of AFP in the serum of cancer patients correlated strongly with standard enzyme-linked immunosorbent assays. These easily fabricated EVC-modified immunosensors show excellent promise for future fabrication of bioelectronic arrays. By varying the target biomolecules, this technique may be easily extended for use with other immunoassays, and thus represents a versatile design route. Full article
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3011 KiB  
Review
Scanning Electron Microscopy with Samples in an Electric Field
by Ludĕk Frank, Miloš Hovorka, Šárka Mikmeková, Eliška Mikmeková, Ilona Müllerová and Zuzana Pokorná
Materials 2012, 5(12), 2731-2756; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122731 - 11 Dec 2012
Cited by 17 | Viewed by 11191
Abstract
The high negative bias of a sample in a scanning electron microscope constitutes the “cathode lens” with a strong electric field just above the sample surface. This mode offers a convenient tool for controlling the landing energy of electrons down to units or [...] Read more.
The high negative bias of a sample in a scanning electron microscope constitutes the “cathode lens” with a strong electric field just above the sample surface. This mode offers a convenient tool for controlling the landing energy of electrons down to units or even fractions of electronvolts with only slight readjustments of the column. Moreover, the field accelerates and collimates the signal electrons to earthed detectors above and below the sample, thereby assuring high collection efficiency and high amplification of the image signal. One important feature is the ability to acquire the complete emission of the backscattered electrons, including those emitted at high angles with respect to the surface normal. The cathode lens aberrations are proportional to the landing energy of electrons so the spot size becomes nearly constant throughout the full energy scale. At low energies and with their complete angular distribution acquired, the backscattered electron images offer enhanced information about crystalline and electronic structures thanks to contrast mechanisms that are otherwise unavailable. Examples from various areas of materials science are presented. Full article
(This article belongs to the Special Issue Low Voltage Electron Microscopy)
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2709 KiB  
Article
Horizontal Bilayer for Electrical and Optical Recordings
by Philipp Bartsch, Claudius Walter, Philipp Selenschik, Alf Honigmann and Richard Wagner
Materials 2012, 5(12), 2705-2730; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122705 - 10 Dec 2012
Cited by 21 | Viewed by 8178
Abstract
Artificial bilayer containing reconstituted ion channels, transporters and pumps serve as a well-defined model system for electrophysiological investigations of membrane protein structure–function relationship. Appropriately constructed microchips containing horizontally oriented bilayers with easy solution access to both sides provide, in addition, the possibility to [...] Read more.
Artificial bilayer containing reconstituted ion channels, transporters and pumps serve as a well-defined model system for electrophysiological investigations of membrane protein structure–function relationship. Appropriately constructed microchips containing horizontally oriented bilayers with easy solution access to both sides provide, in addition, the possibility to investigate these model bilayer membranes and the membrane proteins therein with high resolution fluorescence techniques up to the single-molecule level. Here, we describe a bilayer microchip system in which long-term stable horizontal free-standing and hydrogel-supported bilayers can be formed and demonstrate its prospects particularly for single-molecule fluorescence spectroscopy and high resolution fluorescence microscopy in probing the physicochemical properties like phase behavior of the bilayer-forming lipids, as well as in functional studies of membrane proteins. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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935 KiB  
Review
Organic and Inorganic Dyes in Polyelectrolyte Multilayer Films
by Vincent Ball
Materials 2012, 5(12), 2681-2704; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122681 - 10 Dec 2012
Cited by 17 | Viewed by 6922
Abstract
Polyelectrolyte multilayer films are a versatile functionalization method of surfaces and rely on the alternated adsorption of oppositely charged species. Among such species, charged dyes can also be alternated with oppositely charged polymers, which is challenging from a fundamental point of view, because [...] Read more.
Polyelectrolyte multilayer films are a versatile functionalization method of surfaces and rely on the alternated adsorption of oppositely charged species. Among such species, charged dyes can also be alternated with oppositely charged polymers, which is challenging from a fundamental point of view, because polyelectrolytes require a minimal number of charges, whereas even monovalent dyes can be incorporated during the alternated adsorption process. We will not only focus on organic dyes but also on their inorganic counterparts and on metal complexes. Such films offer plenty of possible applications in dye sensitized solar cells. In addition, dyes are massively used in the textile industry and in histology to stain textile fibers or tissues. However, the excess of non bound dyes poses serious environmental problems. It is hence of the highest interest to design materials able to adsorb such dyes in an almost irreversible manner. Polyelectrolyte multilayer films, owing to their ion exchange behavior can be useful for such a task allowing for impressive overconcentration of dyes with respect to the dye in solution. The actual state of knowledge of the interactions between charged dyes and adsorbed polyelectrolytes is the focus of this review article. Full article
(This article belongs to the Special Issue Advances in Colorants)
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1376 KiB  
Review
Substrate Effects on the Formation Process, Structure and Physicochemical Properties of Supported Lipid Bilayers
by Ryugo Tero
Materials 2012, 5(12), 2658-2680; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122658 - 07 Dec 2012
Cited by 120 | Viewed by 10591
Abstract
Supported lipid bilayers are artificial lipid bilayer membranes existing at the interface between solid substrates and aqueous solution. Surface structures and properties of the solid substrates affect the formation process, fluidity, two-dimensional structure and chemical activity of supported lipid bilayers, through the 1–2 [...] Read more.
Supported lipid bilayers are artificial lipid bilayer membranes existing at the interface between solid substrates and aqueous solution. Surface structures and properties of the solid substrates affect the formation process, fluidity, two-dimensional structure and chemical activity of supported lipid bilayers, through the 1–2 nm thick water layer between the substrate and bilayer membrane. Even on SiO2/Si and mica surfaces, which are flat and biologically inert, and most widely used as the substrates for the supported lipid bilayers, cause differences in the structure and properties of the supported membranes. In this review, I summarize several examples of the effects of substrate structures and properties on an atomic and nanometer scales on the solid-supported lipid bilayers, including our recent reports. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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1413 KiB  
Review
Biotechnology Applications of Tethered Lipid Bilayer Membranes
by Joshua A. Jackman, Wolfgang Knoll and Nam-Joon Cho
Materials 2012, 5(12), 2637-2657; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122637 - 07 Dec 2012
Cited by 100 | Viewed by 13721
Abstract
The importance of cell membranes in biological systems has prompted the development of model membrane platforms that recapitulate fundamental aspects of membrane biology, especially the lipid bilayer environment. Tethered lipid bilayers represent one of the most promising classes of model membranes and are [...] Read more.
The importance of cell membranes in biological systems has prompted the development of model membrane platforms that recapitulate fundamental aspects of membrane biology, especially the lipid bilayer environment. Tethered lipid bilayers represent one of the most promising classes of model membranes and are based on the immobilization of a planar lipid bilayer on a solid support that enables characterization by a wide range of surface-sensitive analytical techniques. Moreover, as the result of molecular engineering inspired by biology, tethered bilayers are increasingly able to mimic fundamental properties of natural cell membranes, including fluidity, electrical sealing and hosting transmembrane proteins. At the same time, new methods have been employed to improve the durability of tethered bilayers, with shelf-lives now reaching the order of weeks and months. Taken together, the capabilities of tethered lipid bilayers have opened the door to biotechnology applications in healthcare, environmental monitoring and energy storage. In this review, several examples of such applications are presented. Beyond the particulars of each example, the focus of this review is on the emerging design and characterization strategies that made these applications possible. By drawing connections between these strategies and promising research results, future opportunities for tethered lipid bilayers within the biotechnology field are discussed. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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1402 KiB  
Article
Polydopamine-Supported Lipid Bilayers
by Souryvanh Nirasay, Antonella Badia, Grégoire Leclair, Jerome P. Claverie and Isabelle Marcotte
Materials 2012, 5(12), 2621-2636; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122621 - 04 Dec 2012
Cited by 24 | Viewed by 11434
Abstract
We report the formation of lipid membranes supported by a soft polymeric cushion of polydopamine. First, 20 nm thick polydopamine films were formed on mica substrates. Atomic force microscopy imaging indicated that these films were also soft with a surface roughness of 2 [...] Read more.
We report the formation of lipid membranes supported by a soft polymeric cushion of polydopamine. First, 20 nm thick polydopamine films were formed on mica substrates. Atomic force microscopy imaging indicated that these films were also soft with a surface roughness of 2 nm under hydrated conditions. A zwitterionic phospholipid bilayer was then deposited on the polydopamine cushion by fusion of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC) vesicles. Polydopamine films preserved the lateral mobility of the phospholipids as shown by fluorescence microscopy recovery after photobleaching (FRAP) experiments. Diffusion coefficients of ~5.9 and 7.2 µm2 s−1 were respectively determined for DMPC and DOPC at room temperature, values which are characteristic of lipids in a free standing bilayer system. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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736 KiB  
Article
Properties of PEMA-NH4CF3SO3 Added to BMATSFI Ionic Liquid
by Norwati Khairul Anuar, Ri Hanum Yahaya Subban and Nor Sabirin Mohamed
Materials 2012, 5(12), 2609-2620; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122609 - 04 Dec 2012
Cited by 28 | Viewed by 6047
Abstract
Polymer electrolyte films, comprising ammonium trifluoromethanesulfonate salt and butyl-trimethyl ammonium bis(trifluoromethylsulfonyl)imide ionic liquid immobilized in poly (ethyl methacrylate) was studied. Structural, morphological, thermal and electrical properties of the polymer electrolyte films were investigated by differential scanning calorimetry, scanning electron microscopy, and impedance spectroscopy, [...] Read more.
Polymer electrolyte films, comprising ammonium trifluoromethanesulfonate salt and butyl-trimethyl ammonium bis(trifluoromethylsulfonyl)imide ionic liquid immobilized in poly (ethyl methacrylate) was studied. Structural, morphological, thermal and electrical properties of the polymer electrolyte films were investigated by differential scanning calorimetry, scanning electron microscopy, and impedance spectroscopy, respectively. Interactions of the salt and ionic liquid with the host polymer were investigated by Fourier transform infra-red spectroscopy. Electrochemical stability of the electrolytes was determined using linear sweep voltammetry and transference numbers corresponding to ionic transport has been evaluated by means of the Wagner polarization technique. The highest conductivity achieved is in the order of 10−4 S cm−1 for the film added with 35 wt % butyl trimethylammonium bis (trifluoromethanesulfonyl)imide. The film has high amorphicity and low glass transition temperature of 2 °C. The film is electrochemically stable up to 1.8 V. The ion transference number in the polymer film is 0.82 and the conductivity behavior obeys Vogel-Tamman-Fulcher equation. Full article
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1632 KiB  
Article
Spectroscopy of Deep Traps in Cu2S-CdS Junction Structures
by Eugenijus Gaubas, Ievgen Brytavskyi, Tomas Ceponis, Vidmantas Kalendra and Audrius Tekorius
Materials 2012, 5(12), 2597-2608; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122597 - 04 Dec 2012
Cited by 5 | Viewed by 5375
Abstract
Cu2S-CdS junctions of the polycrystalline material layers have been examined by combining the capacitance deep level transient spectroscopy technique together with white LED light additional illumination (C-DLTS-WL) and the photo-ionization spectroscopy (PIS) implemented by the photocurrent probing. Three types of junction [...] Read more.
Cu2S-CdS junctions of the polycrystalline material layers have been examined by combining the capacitance deep level transient spectroscopy technique together with white LED light additional illumination (C-DLTS-WL) and the photo-ionization spectroscopy (PIS) implemented by the photocurrent probing. Three types of junction structures, separated by using the barrier capacitance characteristics of the junctions and correlated with XRD distinguished precipitates of the polycrystalline layers, exhibit different deep trap spectra within CdS substrates. Full article
(This article belongs to the Special Issue Compound Semiconductor Materials)
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664 KiB  
Article
Hemostatic Efficiency and Wound Healing Properties of Natural Zeolite Granules in a Lethal Rabbit Model of Complex Groin Injury
by Yunlong Li, Hui Li, Liping Xiao, Lin Zhou, Jianzhong Shentu, Xumin Zhang and Jie Fan
Materials 2012, 5(12), 2586-2596; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122586 - 03 Dec 2012
Cited by 28 | Viewed by 9040
Abstract
Quikclot has been used many years for treating external hemorrhage in the battle field. In this study, the hemostatic performance of NZG-JY (natural zeolite granules from Jinyun, China) was evaluated and compared with Quikclot in a lethal rabbit model of complex groin injury. [...] Read more.
Quikclot has been used many years for treating external hemorrhage in the battle field. In this study, the hemostatic performance of NZG-JY (natural zeolite granules from Jinyun, China) was evaluated and compared with Quikclot in a lethal rabbit model of complex groin injury. Fifty-six anesthetized rabbits were randomized to three different groups: (1) NZG-JY (n = 19); (2) Quikclot (n = 19); and (3) medical gauze (n = 18). Survival was recorded three hours after the application of the hemostatic agents. The wound healing properties of the survived animals (n = 4 for each group) were observed a week later. The clotting efficiency is 100% for the animals in the NZG-JY and the Quikclot group, while only 5.6% in the gauze group. The mortality in the NZG-JY group (21.0%) is significantly less than that in the Quikclot group (52.6%) and the gauze group (66.7%). A good healing property was achieved in all animals that survived in the NZG-JY group, while three quarters of the animals in the Quikclot group had serious necrotic tissue. NZG-JY significantly decreases the mortality in a lethal rabbit model of complex groin injury and demonstrates good healing properties. Full article
(This article belongs to the Special Issue Advances in Mesoporous Materials)
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925 KiB  
Article
Preparation and Mechanical Properties of Photo-Crosslinked Fish Gelatin/Imogolite Nanofiber Composite Hydrogel
by Naozumi Teramoto, Akihiko Hayashi, Kaori Yamanaka, Asako Sakiyama, Asuka Nakano and Mitsuhiro Shibata
Materials 2012, 5(12), 2573-2585; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122573 - 29 Nov 2012
Cited by 38 | Viewed by 11229
Abstract
Fish gelatin (FG) extracted from sea bream scales was reacted with glycidyl methacrylate (GMA), and the product (FG-GMA) was used for photopolymerization using a radical photoinitiator in the presence or absence of imogolite nanofibers in the aqueous solution. The synthesis of FG-GMA was [...] Read more.
Fish gelatin (FG) extracted from sea bream scales was reacted with glycidyl methacrylate (GMA), and the product (FG-GMA) was used for photopolymerization using a radical photoinitiator in the presence or absence of imogolite nanofibers in the aqueous solution. The synthesis of FG-GMA was confirmed by 1H NMR spectroscopy, and photopolymerization of FG-GMA was achieved successfully by irradiation with ultraviolet (UV) light for 3 min to yield translucent composite hydrogels. The concentration of FG-GMA varied from 10% to 30% without imogolite, and that of imogolite varied from 0% to 2.0%. A microtomed gel sample was observed with a transmission electron microscope (TEM), and imogolite nanofibers were found to be dispersed finely in the gelatin matrix. Scanning electron microscope (SEM) observation of the lyophilized gel revealed that it had a porous morphology. Mechanical properties of hydrogels were measured by compression tests using a mechanical tester, and viscoelastic properties were measured using a rheometer. The mechanical strength and storage modulus of the hydrogel increased with an increase of imogolite. Full article
(This article belongs to the Special Issue Advances in Nanoscale Biomaterials)
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2414 KiB  
Review
Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)
by Herbert C. Hoffmann, Marta Debowski, Philipp Müller, Silvia Paasch, Irena Senkovska, Stefan Kaskel and Eike Brunner
Materials 2012, 5(12), 2537-2572; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122537 - 28 Nov 2012
Cited by 120 | Viewed by 16340
Abstract
Nuclear Magnetic Resonance (NMR) spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of [...] Read more.
Nuclear Magnetic Resonance (NMR) spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of the structure, dynamics and flexibility of these materials, as well as for the characterization of host–guest interactions with adsorbed species such as xenon, carbon dioxide, water, and many others. The present review introduces and highlights recent developments in this rapidly growing field. Full article
(This article belongs to the Special Issue NMR in Materials Science)
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430 KiB  
Article
MoO3 Thickness, Thermal Annealing and Solvent Annealing Effects on Inverted and Direct Polymer Photovoltaic Solar Cells
by Sylvain Chambon, Lionel Derue, Michel Lahaye, Bertrand Pavageau, Lionel Hirsch and Guillaume Wantz
Materials 2012, 5(12), 2521-2536; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122521 - 27 Nov 2012
Cited by 58 | Viewed by 10454
Abstract
Several parameters of the fabrication process of inverted polymer bulk heterojunction solar cells based on titanium oxide as an electron selective layer and molybdenum oxide as a hole selective layer were tested in order to achieve efficient organic photovoltaic solar cells. Thermal annealing [...] Read more.
Several parameters of the fabrication process of inverted polymer bulk heterojunction solar cells based on titanium oxide as an electron selective layer and molybdenum oxide as a hole selective layer were tested in order to achieve efficient organic photovoltaic solar cells. Thermal annealing treatment is a common process to achieve optimum morphology, but it proved to be damageable for the performance of this kind of inverted solar cells. We demonstrate using Auger analysis combined with argon etching that diffusion of species occurs from the MoO3/Ag top layers into the active layer upon thermal annealing. In order to achieve efficient devices, the morphology of the bulk heterojunction was then manipulated using the solvent annealing technique as an alternative to thermal annealing. The influence of the MoO3 thickness was studied on inverted, as well as direct, structure. It appeared that only 1 nm-thick MoO3 is enough to exhibit highly efficient devices (PCE = 3.8%) and that increasing the thickness up to 15 nm does not change the device performance. Full article
(This article belongs to the Special Issue Photovoltaic Materials 2012)
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806 KiB  
Review
Degradation Mechanisms for GaN and GaAs High Speed Transistors
by David J. Cheney, Erica A. Douglas, Lu Liu, Chien-Fong Lo, Brent P. Gila, Fan Ren and Stephen J. Pearton
Materials 2012, 5(12), 2498-2520; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122498 - 27 Nov 2012
Cited by 35 | Viewed by 11342
Abstract
We present a review of reliability issues in AlGaN/GaN and AlGaAs/GaAs high electron mobility transistors (HEMTs) as well as Heterojunction Bipolar Transistors (HBTs) in the AlGaAs/GaAs materials systems. Because of the complex nature and multi-faceted operation modes of these devices, reliability studies must [...] Read more.
We present a review of reliability issues in AlGaN/GaN and AlGaAs/GaAs high electron mobility transistors (HEMTs) as well as Heterojunction Bipolar Transistors (HBTs) in the AlGaAs/GaAs materials systems. Because of the complex nature and multi-faceted operation modes of these devices, reliability studies must go beyond the typical Arrhenius accelerated life tests. We review the electric field driven degradation in devices with different gate metallization, device dimensions, electric field mitigation techniques (such as source field plate), and the effect of device fabrication processes for both DC and RF stress conditions. We summarize the degradation mechanisms that limit the lifetime of these devices. A variety of contact and surface degradation mechanisms have been reported, but differ in the two device technologies: For HEMTs, the layers are thin and relatively lightly doped compared to HBT structures and there is a metal Schottky gate that is directly on the semiconductor. By contrast, the HBT relies on pn junctions for current modulation and has only Ohmic contacts. This leads to different degradation mechanisms for the two types of devices. Full article
(This article belongs to the Special Issue Compound Semiconductor Materials)
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441 KiB  
Article
First Principles Study on Electronic Structure and Optical Properties of Ternary GaAs:Bi Alloy
by Lifei Yu, Dechun Li, Shengzhi Zhao, Guiqiu Li and Kejian Yang
Materials 2012, 5(12), 2486-2497; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122486 - 26 Nov 2012
Cited by 42 | Viewed by 8298
Abstract
The electronic structure and optical properties of ternary GaAs:Bi alloy are investigated by first principles calculations. It is found that the band gap of GaAs1-xBix decreases monotonously with the increasing of Bi concentration, resulting in the fundamental absorption edge and [...] Read more.
The electronic structure and optical properties of ternary GaAs:Bi alloy are investigated by first principles calculations. It is found that the band gap of GaAs1-xBix decreases monotonously with the increasing of Bi concentration, resulting in the fundamental absorption edge and main absorption peaks of GaAs1-xBix shifting toward lower energy with the increase of the Bi content. The optical constants of GaAs1-xBix, such as the optical absorption coefficient, refractive index, extinction coefficient and optical conductivity, are greater than those of pure GaAs when x > 3.1%, but less than those of pure GaAs when x < 3.1%, which is primarily decided by the intraband level repulsions between Bi-induced states and host states on the valence bands; the contribution of Bi-6s, Bi-6p orbitals and Ga-4p, Ga-4s orbitals on conduction bands is also crucial. Bi doping plays an important role in the modulation of the static dielectric constant and the static refractive index. These results suggest a promising application of GaAs1-xBix alloy as a semiconductor saturable absorber. Full article
(This article belongs to the Special Issue Compound Semiconductor Materials)
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592 KiB  
Article
A Novel Fractional Order Model for the Dynamic Hysteresis of Piezoelectrically Actuated Fast Tool Servo
by Zhiwei Zhu and Xiaoqin Zhou
Materials 2012, 5(12), 2465-2485; https://0-doi-org.brum.beds.ac.uk/10.3390/ma5122465 - 23 Nov 2012
Cited by 15 | Viewed by 6851
Abstract
The main contribution of this paper is the development of a linearized model for describing the dynamic hysteresis behaviors of piezoelectrically actuated fast tool servo (FTS). A linearized hysteresis force model is proposed and mathematically described by a fractional order differential equation. Combining [...] Read more.
The main contribution of this paper is the development of a linearized model for describing the dynamic hysteresis behaviors of piezoelectrically actuated fast tool servo (FTS). A linearized hysteresis force model is proposed and mathematically described by a fractional order differential equation. Combining the dynamic modeling of the FTS mechanism, a linearized fractional order dynamic hysteresis (LFDH) model for the piezoelectrically actuated FTS is established. The unique features of the LFDH model could be summarized as follows: (a) It could well describe the rate-dependent hysteresis due to its intrinsic characteristics of frequency-dependent nonlinear phase shifts and amplitude modulations; (b) The linearization scheme of the LFDH model would make it easier to implement the inverse dynamic control on piezoelectrically actuated micro-systems. To verify the effectiveness of the proposed model, a series of experiments are conducted. The toolpaths of the FTS for creating two typical micro-functional surfaces involving various harmonic components with different frequencies and amplitudes are scaled and employed as command signals for the piezoelectric actuator. The modeling errors in the steady state are less than ±2.5% within the full span range which is much smaller than certain state-of-the-art modeling methods, demonstrating the efficiency and superiority of the proposed model for modeling dynamic hysteresis effects. Moreover, it indicates that the piezoelectrically actuated micro systems would be more suitably described as a fractional order dynamic system. Full article
(This article belongs to the Special Issue Advances in Microelectromechanical Systems (MEMS) Materials)
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