Polypeptide Materials: New synthetic methods and applications

A review of recent developments in polypeptide synthesis is provided. This article is focused on development of new materials based on polypeptides rather than on reproduction or applications of natural protein-based materials. Synthetic methods fall into two major categories: biological and chemical. The most successful biological approaches utilize cellular protein synthesis machinery to perform the task of assembling the polymeric molecules. Adaptation of this machinery for production of new, artificial polypeptide sequences and use of this machinery for incorporation of artificial amino acids into polypeptides have been the key recent contributions in this area. Advances in chemical polypeptide syntheses include new applications in solid and solution phase peptide coupling reactions as well as advances in the polymerization of a-amino acid-N-carboxyan- hydride (NCA) monomers. The use of transition metal initiators in NCA polymerizations has allowed the preparation of very well defined homopolypeptides and may lead to facile routes into peptide block copolymer materials. The presence of stable, chiral structural elements in polypeptides results in self-assembly into ordered films, composites, and liquid crystals. If their sequences are designed and constructed properly, artificial polypeptides have considerable potential for use in construction of artificial tissues and implants, ordered inorganic/organic composites, and in medical diagnostics and biosensors.     

Packaging methods of fiber-Bragg grating sensors in civil structure applications

Fiber-Bragg grating (FBG) sensors made on bare fibers are easily damaged when handled improperly during and after fabrication. As a protection from such damage, a novel technique for protecting and packaging FBG sensors has been developed and is presented in this paper. To characterize the strain transmission efficiency of the packaged FBG sensors, an analytical finite-element method is used, and the results are compared with the experiments. It is observed that the thickness and Young's moduli of glues have little influence on the strain transmission, especially when the thickness of the glue is less than the diameter of an optical fiber. However, recoating and steel-tube packaging will markedly affect the strain transmission rate. The strain transmission rates decrease with the increase in thickness of the packaging material. Also, the aging problem of the polymide or acrylate coating and epoxy glue must be considered, since the service life of most structures is usually designed for more than 50 years. The metallic recoated FBG sensor developed in this research uses different approaches, such as low-temperature solder welding, which shows no aging problem, to install the sensors in the structures. Based on the simulated and experimental results, the nickel recoating method is shown to have good strain transmission efficiency compared with other packaging methods.     

Magnetic sensors and their applications

Magnetic sensors can be classified according to whether they measure the total magnetic field or the vector components of the magnetic field. The techniques used to produce both types of magnetic sensors encompass many aspects of physics and electronics. Here, we describe and compare most of the common technologies used for magnetic field sensing. These include search coil, fluxgate, optically pumped, nuclear precession, SQUID, Hall-effect, anisotropic magnetoresistance, giant magnetoresistance, magnetic tunnel junctions, giant magnetoimpedance, magnetostrictive/piezoelectric composites, magnetodiode, magnetotransistor, fiber optic, magnetooptic, and microelectromechanical systems-based magnetic sensors. The usage of these sensors in relation to working with or around Earth's magnetic field is also presented.     

Monodisperse hematite porous nanospheres: synthesis, characterization, and applications for gas sensors

Monodisperse α-Fe(2)O(3) porous nanospheres with uniform shape and size have been synthesized via a facile template-free route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy were employed to characterize the product, showing the high quality of the as-prepared α-Fe(2)O(3) porous nanospheres. Furthermore, the α-Fe(2)O(3) porous nanospheres can selectively detect ethanol, formaldehyde and acetic acid, with a rapid response and high sensitivity, from a series of flammable and toxic/corrosive gases, indicating their potential applications for high sensitivity gas sensors.     

Materials for solid-state gas sensors

The major problems in the development of inorganic gas-sensor materials are discussed. The general principle of semiconductor gas sensors is considered, and the band-structure parameters sensitive to the gas-phase composition are determined. Ways of improving sensor selectivity are examined. The composition, microstructure, and gas sensitivity of nanocrystalline SnO₂ and ZnO are investigated. The dopant content and grain size of Ni-doped SnO₂ are optimized for H₂S detection. The prospects of employing systems of two or more nanocrystalline oxides (nanocomposites) for gas detection are discussed     

Nanoscale perspective: Materials designs and understandings in lithium metal anodes

Li metal chemistry is a promising alternative with a much higher energy density than that of state-of-the-art Li-ion counterparts. However, significant challenges including safety issues and poor cyclability have severely impeded Li metal technology from becoming viable. In recent years, nanotechnologies have become increasingly important in materials design and fabrication for Li metal anodes, contributing to major progress in the field. In this review, we first introduce the main achievements in Li metal battery systems fulfilled by nanotechnologies, particularly regarding Li metal anode design and protection, ultrastrong separator engineering, safety monitoring, and smart functions. Next, we introduce recent studies on nanoscale Li nucleation/deposition. Finally, we discuss possible future research directions. We hope this review delivers an overall picture of the role of nanoscale approaches in the recent progress of Li metal battery technology and inspires more research in the future.

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Additive manufacturing and applications of nanomaterial-based sensors

Nanoscale materials possess distinct physical and chemical attributes including size-dependent properties, quantum confinement, high surface-to-volume ratio, and superior catalytic activity. These unique qualities enable sensors with high sensitivity, robustness, and fast time response. As the emergence of the Internet of Things (IoT) demands increased production of sensors, it also provides an impetus for concentrated nanomaterial-based sensor research. Meanwhile, additive manufacturing (AM) of nanomaterial-based sensors is critical to bridge the gap between one-off, lab-scale fabrication and cost-effective, industrial-scale production with high reproducibility. By applying the design flexibility and cost savings of AM techniques, a new generation of nanomaterial-based sensing platforms can be integrated with IoT devices in the consumer space. Furthermore, emergent research in human–machine interfaces, food safety, and point-of-care diagnostics will be expedited by the development of sensors that can be printed with irregular form factors. In this Review, the relative strengths and weaknesses of printed sensor systems based on zero-, one-, and two-dimensional nanomaterials are discussed. In addition, sensors enabled by printable soft nanomaterials, heterostructures, and nanocomposites are surveyed due to their synergistic advantages for wearable healthcare monitoring and soft robotics. Finally, a roadmap for the next decade of research on this topic is provided.     

Space applications of superconductivity: Low frequency superconducting sensors

This is the third of a seven part series on the potential applications of superconductivity in space. Superconducting quantum interference devices (SQUIDs) are used in highly-sensitive magnetometers and gradiometers. They are superior to all other magnetic sensors in sensitivity, frequency response, range, and linearity. They are potentially useful for measuring low-level magnetic field variations in space, such as fluctuations in the solar wind and small- or large-scale spacial anomalies of planetary fields. They are useful also as galvanometers and amplifiers, particularly for applications requiring extreme voltage sensitivity such as, for example, low-impedance bolometer amplifiers. In connection with low-frequency sensors, superconductivity provides some adjunct devices, namely perfect magnetic shields and flux transformers, the latter being used for a number of purposes including construction of fairly elaborate gradiometer pickup-loop arrays.     

PVDF shock sensors: applications to polar materials and high explosives

Ferroelectric polymers (PVDF) with well-defined and precisely known electrical properties are now routinely available from commercial sources. Electrical processing with the Bauer cyclic poling method can produce individual films with well-defined remanent polarization up to 9 /spl mu/C/cm/sup 2/. These polymers provide an unusual opportunity to study the structure and physical properties of materials subjected to shock loading. The behavior of PVDF has been studied over a wide range of pressures using high-pressure shock loading and has yielded well-behaved, reproducible data up to 25 GPa in inert materials. The application of PVDF gauges for recording shock waves induced in polar materials such as Kel-F, PMMA, or in reactive materials is hampered by observations of anomalous responses due to shock-induced polarization or an electrical charge released inside a shock-compressed explosive. A solution using an appropriate electrical shielding has been identified and applied to PVDF for shock measurement studies of Kel-F, and for Hugoniot measurements of high explosives (PH). Furthermore, shock pressure profiles obtained with in situ PVDF gauges in porous HE (Formex) in a detonation regime have been achieved. Typical results of shock pressure profile versus time show a fast superpressure of a few nanoseconds followed by a pressure release down to a plateau level and then by a pressure decay. More accurate measurements are reported with electrically improved PVDF gauges as well as with 0.25 mm/sup 2/ active area PVDF gauges.     

Industrial applications of amplitude-type fiber-optic sensors

Translated from Izmeritel'naya Tekhnika, No. 12, pp. 11–13, December, 1991.     

Acoustic emission sensors for OEM applications

The acoustic emission (AE) technique is concerned with the detection of structure-borne ultrasonic activity that is naturally generated during the operation of all structures, machinery and processes. Most examples of its application involve the purchase and use of commercially available instrumentation by end-users. To satisfy these demands AE instrumentation has evolved into various forms for use by researchers, engineers and craftpersons. The increasing credibility of AE as a robust industrial measurement technique is creating opportunities for AE sensing to be built into machinery by original equipment manufacturers. In this paper, the evolution of AE technology towards an OEM technique is described and illustrated with examples of some of the information AE can provide in the industrial environment     

Vacuum technology applied to solid state chemical sensors, processing, characterization and applications

This chapter will review several solid state chemical sensors with focus on the importance of ultra high vacuum, UHV, for the development of this area. Examples of sensors will be given where processing of sensors and sensing layers as well as characterization of chemical sensors takes place in UHV as well as examples of sensors for operation in UHV. Applications of chemical sensors both already commercialized and still on the research level will be given. Sensor technologies will span from metal oxide sensors, field effect transistor sensors to surface plasmon resonance, SPR, sensors and microcalorimeters. Examples of new challenging novel sensor approaches like sensors based on indirect SPR sensing and ultra sensitive graphene-based sensors for NO₂ detection will also be given.     

Materials and designs for wirelessly powered implantable light-emitting systems

Strategies are presented to achieve bendable and stretchable systems of microscale inorganic light-emitting diodes with wireless powering schemes, suitable for use in implantable devices. The results include materials strategies, together with studies of the mechanical, electronic, thermal and radio frequency behaviors both in vitro and in in-vivo animal experiments.     

Materials with extreme properties: Their structuring and applications

This article is a brief review on syntheses of materials with extreme properties and their modification by plasma processes to obtain different morphological structures. First we illustrate general methodologies on preparation of polycrystalline diamond (PD), nanocrystalline diamond (ND), cubic boron nitride (cBN), diamond/cBN multilayer films by low pressure methods. Since cBN synthesis is more challenging, we place more attention to cBN including its growth, structuring and doping. The structural compatibility of cBN and diamond enables the fabrication of multilayer (superlattices); and we describe such an approach to produce composite materials with even more extreme properties. The superior hardness, extreme thermal conductivity and high chemical stability make diamond and cBN well suited for cutting tool and tribological applications. Although doping of these wide bandgap materials for p- and n-type conductivity is difficult, recent works indicate considerable advancement. The combination of high chemical stability and thermal conductivity with attractive electronic properties makes diamond and cBN suitable for construction of high power electronic devices operating in harsh environments. The development of these applications relies on the ability to design patterns and control the film conductivity. We illustrate that despite diamond and cBN are chemically stable and inert against many chemicals, film patterning and device fabrication is possible with the use of plasma processing. Further, we discuss the fundamental issues involved and demonstrate feasibility for the design of practical applications such as deep-ultraviolet (DUV) detectors and surface acoustic wave (SAW) devices. Finally we discuss the existence of other composite materials with extreme properties that have been only barely investigated, and that present promising alternatives for the future commercial applications.     

Recent advances in computational materials design: methods,applications, algorithms,and informatics

Journal of Materials Science -     

Hydroxylapatite nanoparticles: fabrication methods and medical applications

Hydroxylapatite (or hydroxyapatite, HAp) exhibits excellent biocompatibility with various kinds of cells and tissues, making it an ideal candidate for tissue engineering, orthopedic and dental applications. Nanosized materials offer improved performances compared with conventional materials due to their large surface-to-volume ratios. This review summarizes existing knowledge and recent progress in fabrication methods of nanosized (or nanostructured) HAp particles, as well as their recent applications in medical and dental fields. In section 1, we provide a brief overview of HAp and nanoparticles. In section 2, fabrication methods of HAp nanoparticles are described based on the particle formation mechanisms. Recent applications of HAp nanoparticles are summarized in section 3. The future perspectives in this active research area are given in section 4.     

Hydroxylapatite nanoparticles: fabrication methods and medical applications

Abstract

Hydroxylapatite (or hydroxyapatite, HAp) exhibits excellent biocompatibility with various kinds of cells and tissues, making it an ideal candidate for tissue engineering, orthopedic and dental applications. Nanosized materials offer improved performances compared with conventional materials due to their large surface-to-volume ratios. This review summarizes existing knowledge and recent progress in fabrication methods of nanosized (or nanostructured) HAp particles, as well as their recent applications in medical and dental fields. In section 1, we provide a brief overview of HAp and nanoparticles. In section 2, fabrication methods of HAp nanoparticles are described based on the particle formation mechanisms. Recent applications of HAp nanoparticles are summarized in section 3. The future perspectives in this active research area are given in section 4.     

原子氧对航天材料表面的作用与防护 I原子氧与航天材料的作用

综述了低地球轨道环境下原子氧与航天材料的相互作用及其机制，介绍了原子氧敏感性材料以及它们在低地球轨道环境下的降解情况。