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The recent discovery of the one‐atom‐thick, two‐dimensional graphene layers with exciting properties including superb optical transparency and high mechanical robustness has stimulated extensive research interest for use as an alternative nanowires (NWs) growth platform for applications in next generation, flexible, stretchable, and printable electronic and optoelectronic devices. When combined with the exceptional capabilities of semiconductor NWs including improved light absorption, reduced optical reflectance, enhanced carrier collection, and fast response, the performance of optoelectronic devices could be significantly improved in novel high‐performance, flexible nanodevices. However, the growth of semiconductor NWs on 2D graphene layers is highly challenging owing to the absence of surface dangling bonds on graphene. Intriguingly, the last decade has witnessed a flurry of research activity on the growth of III‐V semiconductor NWs on graphene. In this review, we highlight the significant advancements that have been made in circumventing this challenge to realize the growth of III‐V semiconductor NWs on graphene. We then summarize the recent progress made in the development of graphene‐based NWs devices including photodetectors and solar cells. Finally, a brief conclusion and outlook of the way forward in the growth of semiconductor NWs on graphene is presented.

International journal of ceramic engineering & science 2(2), 76 - 82 (2020). doi:10.1002/ces2.10036, Transparent nanoceramics, synthesized at extreme conditions of high pressure and temperature, are new classes of materials highly attractive for photonic applications, such as optical windows, which require additional increased hardness and toughness. In this study, mechanical properties of transparent polycrystalline nanoceramics consisting of triclinic Al$_2$SiO$_5$ kyanite (~91.4 vol%) and trigonal Al$_2$O$_3$ corundum (~8.6 vol%) fabricated at high pressure (10 GPa) and temperature (1200‐1400°C) were investigated. It is already known that the optical transparency of kyanite‐based nanoceramics increases with decreasing average grain size. The present study shows that the hardness of these ceramics increases with decreasing grain sizes down to ~70 nm according to the Hall‐Petch strengthening. This grain size seems to mark a transition range where an inverse Hall‐Petch effect is indicated due to signs of a moderate hardness decrease at a smaller grain size of ~35 nm. The observed hardness‐grain size relation can fairly be described by an existing composite model, which considers the crystals to be harder than the noncrystalline grain boundaries. Within the range of average grain sizes examined, the kyanite habit changes from more equant to more columnar. This behavior is associated with the observed strong crack deflection by the columnar kyanite grains with aspect (length to diameter) ratios ranging from ~2 to 10 and may positively affect the fracture toughness., Published by Wiley, Hoboken, NJ

We demonstrated thermal curing encapsulation adhesive sheets for the flexible organic light emitting diodes. The thermal curing adhesive sheets were newly designed for the face-sealing encapsulation sheet and had sufficient interface adhesion between the device surface and gas barrier films, high optical transparency, and flexible properties.

Diamond is a highly attractive material for ample applications in material science, engineering, chemistry, and biology because of its favorable properties. The advent of conductive diamond coatings and the steady demand for miniaturization in a plethora of economic and scientific fields resulted in the impetus for interdisciplinary research to develop intricate deposition techniques for thin (≤1000 nm) and ultra-thin (≤100 nm) diamond films on non-diamond substrates. By virtue of the lowered thickness, diamond coatings feature high optical transparency in UV-IR range. Combined with their semi-conductivity and mechanical robustness, they are promising candidates for solar cells, optical devices, transparent electrodes, and photochemical applications. In this review, the difficulty of (ultra-thin) diamond film development and production, introduction of important stepping stones for thin diamond synthesis, and summarization of the main nucleation procedures for diamond film synthesis are elucidated. Thereafter, applications of thin diamond coatings are highlighted with a focus on applications relying on ultrathin diamond coatings, and the excellent properties of the diamond exploited in said applications are discussed, thus guiding the reader and enabling the reader to quickly get acquainted with the research field of ultrathin diamond coatings.

Recent advances in the micromachining of poly(p-xylylenes), commercially known as Parylenes, have enabled the development of novel structures and devices for microelectromechanical systems (MEMS). In particular, Parylene C (poly[chloro-p-xylylene]) has been explored extensively for biomedical applications of MEMS given its compatibility with micromachining processes, proven biocompatibility, and many advantageous properties including its chemical inertness, optical transparency, flexibility, and mechanical strength. Here we present a review of often used and recently developed micromachining process for Parylene C, as well as a high-level overview of state-of-the-art Parylene hybrid and free film devices for biomedical MEMS (bioMEMS) applications, including a discussion on its challenges and potential as a MEMS material. Copyright © 2015 John Wiley & Sons, Ltd.

The desire for foldable display seems to be heading toward its zenith. However, its mass production is still impeded by a few technical challenges, specifically, development of flexible cover window films. This invited paper demonstrates innovative flexible hard coating (Flex9H®) for foldable display cover plastic films, which exhibits glass-like pencil hardness, plastic-like flexibility and excellent optical transparency simultaneously.

This work describes the morphological, optical, and thermo-optical properties of a temperature-sensitive hydrogel poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide) [P(NIPAm-co-NIPMAm]) film containing a specific amount of gold nanorods (GNRs). The light-induced thermoplasmonic heating of GNRs is used to control the optical scattering of an initially transparent hydrogel film. A hydrated P(NIPAm-co-NIPMAm) film is optically clear at room temperature. When heated to temperatures over 37 degrees C via light irradiation with a resonant source (lambda = 810 nm) to the GNRs, a reversible phase transition from a swollen hydrated state to a shrunken dehydrated state occurs. This phenomenon causes a drastic and reversible change in the optical transparency from a clear to an opaque state. A significant red shift (approximate to 30 nm) of the longitudinal band can also be seen due to an increased average refractive index surrounding the GNRs. This change is in agreement with an ad hoc theoretical model which uses a modified Gans theory for ellipsoidal nanoparticles. Morphological analysis of the composite film shows the presence of well-isolated and randomly dispersed GNRs. Thermo-optical experiments demonstrate an all-optically controlled light attenuator (65% contrast ratio) which can be easily integrated in several modern optical applications such as smart windows and light-responsive optical attenuators.

Silicon micropyramids with n(+) pp(+) junctions are demonstrated to be efficient absorbers for integrated solar-driven hydrogen production systems enabling significant improvements in both photocurrent and onset potential. When conformally coated with MoSx Cly , a catalyst that has excellent catalytic activity and high optical transparency, the highest photocurrent density for Si-based photocathodes with earth-abundant catalysts is achieved.

Stretchable and transparent inorganic semiconductors play a key role for the next generation of wearable optoelectronics. Achieving stretchability in intrinsically rigid inorganic materials is far more challenging than in polymers and metals. Here, we present a low-cost and scalable strategy to engineer inorganic semiconductors into a buckling open-mesh configuration, by which extraordinary stretchability (≈160%) as well as high optical transparency (>86% at 550 nm) can be realized simultaneously in SnO2 nanofiber webs. Moreover, the mechanical stretchability of SnO2 nanowebs can be further improved along with the optical transparency by precisely controlling the nanofiber density. The as-prepared freestanding nanowebs can be laminated onto curved surfaces by conformal contact. It is demonstrated that the fully exposed SnO2 nanowebs can be used as wearable UV photodetectors, showing reliable optoelectronic performance and remarkable tolerance to repeated complex deformations with body movements.

A new photo-patternable and thermally-stable organic gate insulator has been developed specifically for IGZO TFTs. Combined with an optimized device platform, flexible IGZO TFTs show groundbreaking performance such as high field-effect mobilities, negligible I-V hysteresis, excellent optical transparency and good thermal and bias-temperature stress stability. A 5" flexible AMOLED utilizes these technologies has been fabricated.

We report on fully flexible and transparent piezoelectric touch sensors based on ZnO nanowires (NWs). Their piezoelectric properties are further enhanced by incorporating BaTiO3 into the capping layer on nanowires. Flexibility is improved by a highly transparent carbon nanotubes–silver nanowires electrode. A BaTiO3-based capping layer on ZnO nanowires demonstrates a large increase of the output voltage (∼3.3 V) from the touch sensor compared to the voltage (∼50 mV). Mechanical bending tests reveal that the BaTiO3-added capping layer did not show significant degradation in change of resistance. Our results suggest that the piezoelectric touch sensors are promising for next-generation flexible touch sensors, wearable, and rollable touch panels.

Biotests performed on small vertebrate model organisms provide significant investigative advantages as compared with bioassays that employ cell lines, isolated primary cells, or tissue samples. The main advantage offered by whole-organism approaches is that the effects under study occur in the context of intact physiological milieu, with all its intercellular and multisystem interactions. The gap between the high-throughput cell-based in vitro assays and low-throughput, disproportionally expensive and ethically controversial mammal in vivo tests can be closed by small model organisms such as zebrafish or Xenopus. The optical transparency of their tissues, the ease of genetic manipulation and straightforward husbandry, explain the growing popularity of these model organisms. Nevertheless, despite the potential for miniaturization, automation and subsequent increase in throughput of experimental setups, the manipulation, dispensing and analysis of living fish and frog embryos remain labor-intensive. Recently, a new generation of miniaturized chip-based devices have been developed for zebrafish and Xenopus embryo on-chip culture and experimentation. In this work, we review the critical developments in the field of Lab-on-a-Chip devices designed to alleviate the limits of traditional platforms for studies on zebrafish and clawed frog embryo and larvae.

Temperature-driven switching of water adhesion is realized on a novel n-paraffinswollen organogel by thermally controlling the transition of air/liquid/solid (ALS/ALLS) systems via the phasechange process of n-paraffin. The thermal control of both the water-drop sliding motion and the switching of the optical transparency shows potential applications in scientific research and daily life.

Here we review the recent research activities on the epitaxial growth of semiconductor nanowires (NWs) on graphene substrates. Semiconductor NWs with quasi one-dimensional structure have become an active research field due to their various interesting physical properties and potentials for future electronic and optoelectronic device applications, such as transistors, sensors, solar cells, light emitting diodes, and lasers. At almost the same time graphene, a two-dimensional material made of carbon, was discovered and has gained an ever increasing interest during the last few years owing to its remarkable properties, including excellent electrical conductivity, optical transparency, and mechanical strength and flexibility. A hybrid structure by epitaxially growing semiconductor NWs on graphene could provide a new avenue for the development of future advanced NW-based flexible electronic and optoelectronic devices. We address the challenges for the growth of semiconductor NWs on graphene, with a special focus on the III–V semiconductors, and highlight some potential applications of the NW/graphene hybrid system. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A polymer-layered silicate nanocomposite coating is prepared by combining a novel synthetic lithium-hectorite and an UV-curable, cationic polyurethane. Oxygen transmission measurements clearly indicate the supremacy of the lithium-hectorite as compared to a standard montmorillonite. In addition, a very high degree of optical transparency of the nanocomposite coating is achieved, rendering this material highly interesting for flexible packaging and encapsulation applications.

A high level of optical transparency (over 65%) has been obtained in hydroxyapatite ceramics. This optical transparency arises due to a combination of the texture, measured as the extent of an in-plane orientation of the crystallographic c-axis, and the physical density. The highest value of transparency is observed in pellets sintered at 900°C, below which the transmittance declines due to a decline in the density and texture. Above 900°C, the transmittance declines again due to a loss in the c-axis orientation.

Development of hydrogel materials that respond to specific stimuli has been of significant interest in the design of modern functional materials. A variety of previous studies have used the ligand-binding capability of proteins to design hydrogels that change their crosslinking density in response to stimuli. However, these materials generally undergo relatively small dynamic response, with limited control over response characteristics. This manuscript describes an alternative approach that exploits the ability of proteins to undergo nanometer-scale conformational changes in response to stimuli. We report a class of novel protein-based hydrogel materials that undergo tunable, reversible dynamic responses with a wide dynamic range (volume decreases to ∼25–90% of initial volume). These materials also undergo tunable, reversible changes in optical transparency (optical transparency decreases to ∼35–100% of initial optical transparency), and this phenomenon is used as a mechanism for label-free biosensing. The materials are generated by photo-crosslinking of an engineered version of the protein calmodulin flanked on each end with poly(ethylene glycol)-diacrylate (PEGDA) moieties. The mechanism for dynamic changes derives from calmodulin's well-characterized “hinge motion”-upon-ligand binding. Variations in network parameters in these hydrogels, including the molecular weight between cross-links and the cross-linking density, result in systematic tuning of material responsiveness. The influence of network parameters on hydrogel dynamics reported here may serve as a guide for the design of other protein-based, responsive materials assembled using similar principles, and these materials may be a useful platform for design of biosensors, actuators, and drug delivery systems.

Parent glasses for fabricating glass–ceramics with nanometer-sized crystals usually have high viscosities, resulting in high processing temperatures. In this study, GeO2 was added to a transparent, near-zero thermal-expansion Li2O–Al2O3–SiO2 glass–ceramic to reduce the viscosity of the parent glass. The effects of this compositional modification on the viscosity and crystal-nucleation rate of the parent glasses, and on the crystal size, thermal expansion, and optical transparency of the resulting glass–ceramics were investigated. It was found that addition of GeO2 was useful in reducing the glass viscosity. Owing to the reduced nucleating rate with the increase in the GeO2 content, the nucleating times required for reaching the smallest crystal size, the lowest coefficient of thermal expansion, and the highest transparency were all increased. With increasing GeO2 content, the lowest coefficient of thermal expansion that can be reached for glass–ceramics increased (0.14–2.9 × 10−6 K−1). The highest transparency of the GeO2-containing glass–ceramics is almost as good as that of the GeO2-free glass–ceramic and is almost independent of GeO2 content when the crystal size is smaller than about 65 nm.

This contribution reports a simple, straightforward method (cool sputtering) of fabricating robust, homogeneous, conductive, and optically transparent ultrathin Pt films. Their morphological, structural, mechanical, electrical, and optical properties are reported. The morphology and structure of these Pt films are investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X-ray diffraction. The ultrathin Pt films, approximately 20 nm thick, are characterized by a homogenous, polycrystalline structure, with a tendency to adopt a (111) texture upon the thermal treatment. Moreover, thermal treatment (annealing or flaming) of the as-prepared films also substantially improves their chemical and mechanical robustness. F films behave as bulk Pt in terms of electrical resistivity and suitability as working electrodes in cyclic voltammetry experiments. Overall, the unique combination of these excellent features: homogeneity, robustness, and conductivity, in addition to the high optical transparency in the 300-800 nm range of the electromagnetic spectrum, make ultrathin Pt films appropriate for a variety of applications in the field of molecular optoelectronics. The formation of functional molecular self-assembled monolayers (SAMs) on these transparent, conductive films allows their optical monitoring using transmission optical spectroscopy, as well as the probing of their electrical properties. The potential of such Pt films as suitable metal substrates in opto- and nanoelectronics is proven by representative applications, including switching of prototypical photochromic and electrochromic species in SAMs and molecule-metal junctions.

An overview of the electrochemistry of poly(3,4-alkylenedioxythiophene)s (PXDOTs) is presented. As a class of conducting and electroactive polymers that can exhibit high and quite stable conductivities, a high degree of optical transparency as a conductor, and the ability to be rapidly switched between conducting doped and insulating neutral states, PXDOTs have attracted attention across academia and industry. Numerous fundamental aspects are addressed here in detail, ranging from the electrochemical synthesis of PXDOTs, a variety of in-situ characterization techniques, the broad array of properties accessible, and morphological aspects. Finally, two electrochemically-driven applications, specifically electrochromism and chemical sensors of PXDOTs are discussed.

Poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate) (PHF) is miscible with poly(hydroxyether of bisphenol-A) (phenoxy) as shown by the optical transparency and a single glass-transition temperature in each blend. FTIR spectroscopy shows that the interactions between PHF and phenoxy are not particularly strong. The surface properties of the blends were studied by contact angle measurements, dynamic and static time-of-flight secondary ion mass spectroscopy, and X-ray photoelectron spectroscopy. The blend surfaces were enriched with PHF. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1798–1805, 2004

Optically transparent metamaterial microwave absorbers (MMAs) developed so far unexceptionally encounter an intrinsic contradiction between extending the absorption bandwidth and improving optical transparency, hindering their practical applications. This work, in its experiment and calculation, demonstrates an MMA with both broadband microwave absorption and excellent optical transparency by standing-up closed-ring resonators (CRRs) in an indium tin oxide backed Plexiglas board. The as-designed MMA shows a strong microwave absorption of 85% covering a wide frequency of 5.5–19.7 and 22.5–27.5 GHz up to a large incident angle of 70o due to the electric and magnetic resonances caused by the standing-up arrangement of the CRRs, as well as the multiple reflection mechanism. Moreover, in sharp contrast to the widely adopted stacking multiple layers at the expense of greatly reduced optical transparency, it has an optical transmittance of around 82%, as calculated by a transfer matrix method. The standing-up MMA proposed here provides an effective way to achieve broadband microwave absorption and high compatibility with optical transparency, enabling wide applications in window glass of stealth armament and electromagnetic compatible buildings/facilities.

A flexible hard coating for foldable displays is realized by the highly cross-linked siloxane hybrid using structure-property relationships in organic-inorganic hybridization. Glass-like wear resistance, plastic-like flexibility, and highly elastic resilience are demonstrated together with outstanding optical transparency. It provides a framework for the application of siloxane hybrids in protective hard coatings with high scratch resistance and flexibility for foldable displays.

A single-chamber system capable of depositing both organic and inorganic layers by initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) is demonstrated to facilitate the fabrication of organic/inorganic hybrid thin film encapsulation (TFE). The chamber geometry and the process conditions of iCVD and ALD are similar to each other, which enabled the design of the single-chamber system. Both organic and inorganic films deposited via the single-chamber system produces films with their properties equivalent to those deposited in separate iCVD and ALD reactors. Alternating the deposition mode between iCVD and ALD produces organic/inorganic multilayers with outstanding barrier properties as well as optical transparency mechanical flexibility.

The miscibility of five chitosan/tertiary amide polymer blend systems was studied. Based on the optical transparency of the blend and the existence of a single glass transition temperature, chitosan was found to be miscible with poly(N-vinyl-2-pyrrolidone), poly(N-methyl-N-vinylacetamide), poly(N,N-dimethylacrylamide), poly(2-methyl-2-oxazoline), and poly(2-ethyl-2-oxazoline). Fourier transform infrared spectroscopy showed the existence of hydrogen-bonding interactions between chitosan and the tertiary amide polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1785–1790, 2000

Partial imidization of poly[(amic ester)-alt-(amic acid)], a precursor for the strictly alternating copolyimides, was performed via selective chemical imidization of amic acid units in the copolymer precursor. The resulting, poly[(amic ester)-alt-imide], showed superior properties such as an excellent solution stability, good processibility and improved optical transparency, which are essential for the use as a precursor for the polyimide.

Poly(ethylene terephthalate) (PET)/clay, PET/poly(ethylene glycol-co-1,3/1,4-cyclohexanedimethanol terephthalate) (PETG), and PET/PETG/clay nanocomposites were fabricated using the twin-screw extrusion technique. The spherulitic morphologies, thermomechanical, mechanical, and gas-barrier properties, as well as the effect of clay on the transparency of the resulting nanocomposites were identified. The clay induced the heterogeneous nucleation of the nanocomposites during the cold crystallization process, thereby increasing the crystallinities and melting temperatures of the resulting nanocomposites. The incorporation of clay increased the storage moduli, Young's moduli, impact strengths, and barrier properties of the PET, PETG, and PET/PETG blend. Regarding the optical transparency, the inclusion of clay can make the crystallizable PET matrix crystalline opaque. However, the amorphous PETG maintained its transparency. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39869.

Two-phase α/β composites have been produced with a combination of high hardness, fracture toughness, and strength. Compared with a single-phase α-sialon, the composite showed around a twofold increase in both fracture toughness and bending strength, with only minimal reduction in hardness. Despite being a two-phase material, the optical properties of the composite were very good, showing transparency in sections of around 0.5 mm thickness. The optical properties were in fact better for the composite than for the single-phase α-sialon. Work to date on transparent sialons has focused on single-phase α-materials, which have inherently low fracture toughness unless elongated microstructures are developed. However, this microstructural development appears to adversely affect optical transparency. In this work it has been shown that good combination of mechanical properties can be achieved while maintaining optical transparency in two-phase composite sialons. The development of such materials should widen their range of application.

Ordered hexagonal arrays of parallel collagen fibers produce the brilliant green structural color of the fleshy, supraorbital caruncles of male Velvet Asity (Philepitta castanea; Aves: Eurylaimidae). The collagen arrays are organized in larger macrofibrils that are packed irregularly within cone-shaped papillae that cover the surface of the caruncle. The color of the caruncle conforms closely to the wavelengths predicted by applying Bragg's Law of constructive reflection to measurements of the size and spatial organization of the collagen arrays. These observations constitute a novel mechanism of structural color production in animals. These collagen arrays are convergently similar to the smaller, highly structured collagen arrays in the mammalian cornea, which exploit the same physical mechanism to produce optical transparency. © 1994 Wiley-Liss, Inc.

Development of advanced photonic devices requires extensive integration of several technologies. Electrooptical devices must simultaneously satisfy several materials properties including: high nonlinear optical activity, thermal stability, mechanical strength, and optical transparency. In addition, the device materials must be amenable to fabrication, and must be compatible in a multi-layered configuration. We have recently developed polymers which meet these complex requirements. Indeed, electrooptical devices have been demonstrated using these polymers. This paper is a comprehensive review of the development of such devices, from design of the molecular architecture to waveguide design and fabrication. The critical issues in each aspect of device development are discussed. © 1994 John Wiley & Sons, Inc.

A series of linear aromatic polyimide films that are based on a novel methylene-bridged dianhydride, 3,3′-bis(3,4-dicarboxyphenoxy) diphenylmethane dianhydride, have been synthesized and characterized. High molecular weight polyamic acids were prepared by combining this dianhydride with numerous aromatic diamines. The effects of thermal and chemical imidization of the polyamic acids are discussed as they relate to the dielectric constant, optical transparency, and solubility of the resulting polyimide films. The objective of this work was to obtain low dielectric, optically transparent, and soluble polyimides that can be easily processed as coatings or composite matrices for advanced aerospace and electronics applications.

Polyimides [N(CO) 2 Ar(CO) 2 N-Ar'] n (Ar= Ph, PhCOPh, PhPh, PhSO 2 Ph, PhC(CF 3 ) 2 Ph; Ar'= PhOPhC(CF 3 ) 2 PhOPh, PhOPhC(CH 3 ) 2 PhOPh) by solution polymerization followed by thermal imidation. The polymers had T g higher than 200°C and were thermally stable up to 450°C. The fluorinated polyimide films had good optical transparency and low dielectric constant

We report several kinds of interpenetrating polymer networks (IPNs) with nonlinear optical (NLO) properties. DMA spectra show that the two components of the IPNs have good compatibility with each other. The NLO materials have good optical transparency. The thermal stability of alignment was improved and the poled order remained very high. (C) 1999 John Wiley & Sons, Inc.

The non-centrosymmetric compounds Mg(IO3)2, Mn(IO3)2, Co(IO3)2 and Zn(IO3)2 are isostructural and crystallise in space-group type P 2 1 with a pseudo-hexagonal lattice leading to the formation of a three-individual twin by pseudo-merohedry. Because of this structural analogy, solid solutions are possible between these metallic iodates. Bimetallic iodates Mn1−xZnx(IO3)2 form a solid solution over the entire domain of composition. Second harmonic generation test and absorption studies carried out on theses materials show high nonlinear activities, high damage thresholds and are transparent up to 12 μm in the IR.