Current Smart Materials - Volume 3, Issue 2, 2018

Fluorescent probes exhibit the characteristics of high sensitivity, diversified design, and strong quantitative analysis ability. Therefore, they have become one of the research hotspots in analytical chemistry and biological analysis. Aptamers are single-stranded DNAs or RNAs that are obtained in vitro and can selectively bind to the targets, making them ideal candidates as identifying units in fluorescent probes. However, most of the current aptamer probes are not regulatable because their fluorescence signals can’t be changed after the fluorescent probes are bound to the target, resulting in a high signal background and limited contrast. Actually, the structure of aptamers is flexible and can be combined with a variety of nanomaterials to achieve high sensitivity fluorescence for quantitative analysis, and can be used for a variety of target determinations, such as metal ions, small molecules, proteins and cells. In addition, with the development of research on DNA nanotechnology, researchers have designed many aptamer-based fluorescent probes with special properties, which have good application prospects in complex sample analyses and even in vivo cell imaging. In this review, the development of research in the field of aptamer-based fluorescent probes is surveyed and four mechanisms of aptamer fluorescent probes, including dye intercalation, conversion of DNA conformation, signal amplification, and mediation of nanomaterials, are comprehensively discussed.

Shape Memory Alloys (SMAs) have revolutionized the materials engineering science due to their super-elasticity (SE) and Shape Memory Effect (SME). They recover their shape upon heating or by removing load. Nitinol is the most famous SMA but the research reveals that Ferrous based Shape Memory Alloys (Fe-SMAs) have a great potential to be the counterpart of Nitinol. These Fe- SMAs are effective due to their low cost, high cold workability, good weldability & excellent characteristics comparing with Nitinol. Fe-Mn-Si SMAs have a great potential for civil engineering structures. Further research is being conducted on SMAs to improve and impinge better attributes by improving the material compositions and quantifying the SMA phase transition temperatures. In this research, a detailed review of different types of biaxial loadings has been performed and Fe-SMA’s publications and US Patents data related to different types of biaxial loading have been compared with that of different linear elastic isotropic materials (e.g. Steel, Aluminium, and Copper) & nonlinear smart materials (e.g. Nitinol). All the above-mentioned data and their comparison have also been tabularized in this work. It has been observed that Publications and US Patents for different categories of biaxial loadings of Fe-SMAs are negligible as compared to that of other linear elastic isotropic materials and far less comparing with Nitinol. The keywords related to different biaxial loadings of Fe-SMAs, do not exist at all in the title of the article but exist inside few articles. The histograms have been drawn for a clear understanding of the results. It has been concluded that there must be research investigating biaxial loading applications of these valuable Fe-SMAs.

Background: In recent years, the textile fibres and fabrics enriched with multifunctional properties have gained much attention and accepted abundantly. In general, the flame-retardation ability to the textile substrates is endowed with one of the most attentive factors that needed applicability in civilian as well military area. Specific chemical bonding in several textile materials (i.e. cotton, linen, hemp; silk & wool; nylon; polypropylene; polyester) acquired specificity towards implanting flame-retardancy. The present review encompasses various finishing agents being used to develop the flame-resistant property and their aspects to sensitization and durability against several washing cycles with future research-oriented opportunities. Results: With existing flame retarding materials, various new substituted technologies, finishing agents and active materials are being developed to meet the challenge and needs of ever-changing safety regulations. It is an interdisciplinary development that involves quite a lot of scientific and engineering tools. In the present review, various finishing agents being used to develop the durable flame-resistant property are discussed with possible future directions. Conclusion: All the textile materials, i.e. cellulosic (cotton, linen), proteinaceous (silk, wool), and synthetic (nylon, polyester, polypropylene), including fibres/fabrics/blends, have been extensively used, especially in military and civilian area enriched with high comfort nature and several mechanical properties. Except for wool that is significantly fire-resist, other textile fibre abundantly possesses low fire retardancy and, requires further additional chemical processing towards implanting flame retardancy. Nevertheless, most of the flame retardants have been observed to have bad impacts/effects on the environment and associated with skin related to human health. Novel technologies and innovative products are being under considerations to bottom down the present challenges and issues. This would help to make cleaner substitutes for sincerely harmful conventional flame retardant finishing agents and to explore new opportunities in the textile industry and R& D sector.

Background: This paper addresses the moisture sensitivity of Elvaloy-Modified Asphalt (EMA) in the presence of lime using Atomic Force Microscopy (AFM). The performance of three different lime percentages was evaluated for three different levels of EMA. The lime-modified EMA was conditioned for dry and wet environments and finally tested using AFM. All the AFM tests were performed using functional groups of asphalt binder: ammin (NH3), methyl (CH3), carboxyl (COOH), and hydroxyl (OH). Differences of adhesion/cohesion forces for dry and wet samples indicated nano-scale moisture damage. Conclusion: The study found that an increase in percentage of lime from 0.5% results in incremental damage due to moisture. Similarly, for a specific percentage of lime, moisture damage decreases with increased percentage of elvaloy. The use of 0.5% lime with 1.5% EMA outperforms all other combinations in resisting moisture damage and is proposed as the recommended dose for practical purposes.

Background: Smart materials are able to ensure adaptability to changing environmental conditions by varying in real time their dynamical and rheological properties. Magneto-Sensitive Elastomers (MSE) are a special class of such smart materials that can be switched by a magnetic field. They consist of an insulating polymer matrix in which magnetic filler particles are embedded. The presence of an external magnetic field yields to a coupling between the dynamical-mechanical and the magneto-rheological behavior of the MSE. This enables to actively adapt their responses to surrounding conditions. Methods: The magneto-rheological responses of the MSE were investigated with a plate-plate rheometer equipped with a magnetic measuring cell. Both melts and cross-linked rubbers were characterized in the presence of a magnetic field. The measurements were performed by applying a small shear strain of 0.1% and a frequency of 10 Hz. The direction of shearing was perpendicular to the particle orientation and field direction. Results: It is demonstrated how the magnetic filler content and particle orientation influence the properties of the MSE. Dynamical-mechanical and magnetorheological measurements show that the orientation of the magnetic filler particles, achieved due to curing in an external magnetic field, has a strong influence on the stiffness and the magneto-sensitivity of the samples. The magneto-rheological effect increases with filler content but reaches a maximum at about 20 vol.% of magnetic filler particles. Conclusion: Magneto-rheological investigations of the non-cross-linked samples indicate that the magnetic filler particles align themselves into strings once the external magnetic field is turned on. They owe this behavior due to strong magnetic dipole-dipole interactions between adjacent particles. This string structure delivers a pronounced contribution to the shear moduli and magneto-sensitivity of the samples.

Background: Dyeing of textiles and textile substrates has been known since ancient times. Now the increased awareness about natural products, use of eco-friendly products has been increased worldwide. Natural colorants from wastes may be the eco-friendly alternate towards this approach of finding new sources of colorants with simultaneous lowering of environmental pollution. Marigold is one of the wastes discarded, particularly in India after using for religious purposes or garlands. This study is a step towards waste utilization for industrial application. Methods: Extraction of natural colorants (carotenoids) from marigold flowers was carried out and characterized via UV/Visible and FT-IR spectroscopy. Mordanting of wool by three mordants; alum, iron and tin is followed by dyeing of wool fibers by marigold dye. Dyed wool fiber samples were tested for colorimetric and fastness properties. Results: Spectroscopic techniques (UV/Visible and FT-IR) established the final structure of carotenoids, the coloring compounds in Marigold. Marigold dye imparted yellow colored shades on wool. Colorimetric results are excellent in terms of exclusivity of the shades by application of various mordants. Fastness results in terms of washing, light exposure and rubbing were found in practically acceptable range. Conclusion: Dyeing potential of marigold was evaluated. Production of large range of shades with good colorimetric and fastness results on the application of mordants and their combinations successfully evaluated. Mordant combinations used in this study have not been found with satisfactory results relatively but developed exclusive shades. T. erecta natural dye can provide bright hues with good color fastness properties with metallic mordants.