Tunability In Terms Research Articles

Clickable Dynamic Bioinks Enable Post-Printing Modifications of Construct Composition and Mechanical Properties Controlled over Time and Space.

Bioprinting is a booming technology, with numerous applications in tissue engineering and regenerative medicine. However, most biomaterials designed for bioprinting depend on the use of sacrificial baths and/or non-physiological stimuli. Printable biomaterials also often lack tunability in terms of their composition and mechanical properties. To address these challenges, the authors introduce a new biomaterial concept that they have termed "clickable dynamic bioinks". These bioinks use dynamic hydrogels that can be printed, as well as chemically modified via click reactions to fine-tune the physical and biochemical properties of printed objects after printing. Specifically, using hyaluronic acid (HA) as a polymer of interest, the authors investigate the use of a boronate ester-based crosslinking reaction to produce dynamic hydrogels that are printable and cytocompatible, allowing for bioprinting. The resulting dynamic bioinks are chemically modified with bioorthogonal click moieties to allow for a variety of post-printing modifications with molecules carrying the complementary click function. As proofs of concept, the authors perform various post-printing modifications, including adjusting polymer composition (e.g., HA, chondroitin sulfate, and gelatin) and stiffness, and promoting cell adhesion via adhesive peptide immobilization (i.e., RGD peptide). The results also demonstrate that these modifications can be controlled over time and space, paving the way for 4D bioprinting applications.

Arrayed and entangled silicon nanowires using Au nanoparticle catalysts prepared by pulsed laser-induced dewetting

The use of pulsed laser-induced dewetting (PLiD) is reported as a novel approach in the fabrication of Au nanoparticle (NP) catalytic arrays for the growth of Si nanowires (NWs) by chemical vapor deposition using SiCl4 in the presence of H2. On polished Si substrates, PLiD generates Au NP catalysts with long-range order and narrow size distributions. It has been shown that the monodispersed distribution of Au NPs provides consistent diameter control of the as-grown Si NWs. A systematic exploration of the Si NW synthesis time, temperature, and gas flow rates illustrates a level of tunability in terms of morphology, be it arrayed or entangled Si NWs, with varying experimental parameters. An investigation of the effect of growth temperature also showed that Si NWs can be synthesized at temperatures as low as 700 °C when using SiCl4 as the precursor. The use of porous Si substrates enabled direct observation of the diameter-dependent growth due to the simultaneous presence of three Au NP size distributions. Growth from the small- and medium-sized Au NP catalysts occurred first, followed by that from the large-sized Au NPs, which was only observed at extended times or high SiCl4 flow rates. The delayed onset of growth from the large-sized Au NPs is due to the longer time to achieve Si super-saturation of larger catalyst NPs. The morphology and diameter control of the as-grown Si NWs reported in this work makes this approach potentially useful toward applications such as nanoelectronics, sensors, and lithium ion battery electrodes depending on the desired morphology.

Tunable Photonic Band Gaps in Two-Dimensional Bravais–Moiré Photonic Crystal Composed of High-Tc Superconductors

In this study, we perform a theoretical study of light propagation properties in two-dimensional square photonic crystals (PCs) following Bravais–Moiré (BM) patterns composed of copper oxide high-temperature superconductors (HTSCs). The BM PCs are made of cylindrical cores formed from the combination of two square Bravais lattices. The Moiré pattern forms due to a commensurable rotation of one of these lattices with respect to the other. The dielectric function of the superconducting material is modeled by the two-fluid Gorter–Casimir theory. We report on the corresponding gap, the mapping as a function of the radius of dielectric cores, as well as the dispersion relations of TM modes for BM PCs and for the waveguide system built of defect lines within such a crystal. The BM PCs were composed of copper oxide HTSCs, which exhibit large tunability in terms of temperature.

Multistate spectral-tunable manipulation of mid-infrared emissivity using Sb2S3/GST/VO2

Conventional thermal emission that exhibits spectral selectivity relies on micro/nanostructures, such as gratings, photonic crystals, photonic cavities, nanoantennas, and metamaterials. By utilizing advanced micro/nanofabrication techniques to modify the structural parameters of the micro/nanostructures, it is possible to create wavelength-selective thermal emitters that span from THz to the visible range. Nonetheless, static micro/nanostructures do not offer flexible tunability in terms of thermal emissivity. In this Letter, we report a conceptual design of a multistate multilayered structure using a combination of three phase change materials: VO2, Ge2Sb2Te5, and Sb2S3. By controlling the temperature, the phase change materials will be in different phase states, rendering the multilayered structure six feasible thermal states with tunable spectra in the mid-infrared range. The impact of layer thickness is investigated. Polarization independence and angle insensitivity are exhibited until a large incident angle. This multilayered thermal structure is lithography-free and industrially scalable, showing great potential for programmable photonics and thermal sensors.

Vertically‐Stacked Discrete Plasmonic Meta‐Gratings for Broadband Space‐Variant Metasurfaces

AbstractReexamining the plasmonic metasurfaces for efficient transmissive nanophotonics devices has recently drawn considerable attention. It attributes to their ease of fabrication and tunability in terms of the excitation of abundant multipoles. Despite recent efforts in developing plasmonic meta‐atoms, meta‐gratings provide an ultimate solution that enables efficient conversion of the polarization in a broadband range, particularly at optical frequencies. In this work, by vertically stacking meta‐gratings whose bandwidths overlap with each other and possess no physical limitation, plasmon mode hybridization is introduced so that highly‐transmissive broadband plasmonic metasurfaces are realized. It is reported that the intra‐coupling in a discrete plasmonic meta‐grating plays a key role in geometric phase‐controlled metasurface design. As a proof of concept, a half‐wave plate using plasmonic meta‐gratings to convert the incident circularly‐polarized light in a wavelength range from 1106 to 1521 nm with a peak efficiency of 50.2% and a gradient metasurface with truncated discrete meta‐grating as building blocks for deflecting the light with a maximum of 32.60% are demonstrated. Finally, the physical picture is explained through the electric field distributions, mode coupling, and energy splitting. The presented framework may provide an optimized way to enhance efficiency and expand the bandwidth for plasmonic systems.

Nanofluidic Attenuation of Metal-Organic Frameworks

Porous materials with energy absorption characteristics have been used for attenuation against hazardous vibrations and noises. The intrusion of liquid water and aqueous solutions into hydrophobic nanoporous materials such as metal-organic frameworks (MOFs) present an attractive pathway to engineering new attenuation technologies. In this process, hydrostatic pressure forces water to intrude hydrophobic nanopores, thereby converting mechanical work into interfacial energy through nanoscale interfacial interactions. Once the external pressure is removed, water molecules can flow out of the nanopores spontaneously, making the system reversible. We envision that this mechanism has the potential of innovating attenuation technologies, so in this work we provided a preliminary study in this direction. We investigated a material system consisting of water and a commonly used MOF, zeolitic imidazolate framework-8 (ZIF-8), and demonstrated its reversibility and stability under cyclic pressurization, considered its performance at various peak pressures and frequencies, its tunability in terms of intrusion pressure, and its potential in hydrogel forms. These features are important for potential attenuation technologies based on this novel mechanism.

Fluorescent Multifunctional Organic Nanoparticles for Drug Delivery and Bioimaging: A Tutorial Review.

Fluorescent organic nanoparticles (FONs) are a large family of nanostructures constituted by organic components that emit light in different spectral regions upon excitation, due to the presence of organic fluorophores. FONs are of great interest for numerous biological and medical applications, due to their high tunability in terms of composition, morphology, surface functionalization, and optical properties. Multifunctional FONs combine several functionalities in a single nanostructure (emission of light, carriers for drug-delivery, functionalization with targeting ligands, etc.), opening the possibility of using the same nanoparticle for diagnosis and therapy. The preparation, characterization, and application of these multifunctional FONs require a multidisciplinary approach. In this review, we present FONs following a tutorial approach, with the aim of providing a general overview of the different aspects of the design, preparation, and characterization of FONs. The review encompasses the most common FONs developed to date, the description of the most important features of fluorophores that determine the optical properties of FONs, an overview of the preparation methods and of the optical characterization techniques, and the description of the theoretical approaches that are currently adopted for modeling FONs. The last part of the review is devoted to a non-exhaustive selection of some recent biomedical applications of FONs.

Biomechanical properties of cylindrical and twisted triply periodic minimal surface scaffolds fabricated by laser powder bed fusion

In this study, novel TPMS-based scaffolds with twisted feature were rationally designed and additively manufactured using laser powder bed fusion (LPBF) for mimicking the properties of human bones. Experimental and computational analyses of their morphological features, manufacturability, mechanical properties, and permeability were conducted. It was found that the porosity, surface area, and deviation of the specimens were affected by the change of twist angle. In terms of mechanical properties, the manufactured scaffolds yielded favorable performance to provide ample mechanical support for bone tissue regeneration. The measured mechanical values were all in accordance with those of human bones. The results showed that the twist angle could affect the compressive response, leading to adjustable elastic modulus and compressive strength. It was also observed that the permeability of the twisted scaffolds was in the range of values reported for human bones. The experimental and computational results demonstrated the effects of the twist angle on the mass transport properties. In addition, in vitro studies were conducted for assessing the biocompatibility of the fabricated scaffolds. In summary, the developed twisted porous metallic scaffolds are shown as potential candidates to tailor the properties of bone-substituting biomaterials with tunability in terms of the topological, mechanical, and mass transport properties. • Novel TPMS sheet scaffolds with twisted feature were designed and fabricated by LPBF. • The effects on biomechanical properties of twist angle were investigated. • The effects of twist angle varied among scaffolds with different TPMS types. • The biomechanical properties of twisted scaffolds were found to be in the range of human bones. • The potential applications of twisted TPMS sheet scaffolds were initially validated and further discussed.

A Guide to Polysaccharide-Based Hydrogel Bioinks for 3D Bioprinting Applications.

Three-dimensional (3D) bioprinting is an innovative technology in the biomedical field, allowing the fabrication of living constructs through an approach of layer-by-layer deposition of cell-laden inks, the so-called bioinks. An ideal bioink should possess proper mechanical, rheological, chemical, and biological characteristics to ensure high cell viability and the production of tissue constructs with dimensional stability and shape fidelity. Among the several types of bioinks, hydrogels are extremely appealing as they have many similarities with the extracellular matrix, providing a highly hydrated environment for cell proliferation and tunability in terms of mechanical and rheological properties. Hydrogels derived from natural polymers, and polysaccharides, in particular, are an excellent platform to mimic the extracellular matrix, given their low cytotoxicity, high hydrophilicity, and diversity of structures. In fact, polysaccharide-based hydrogels are trendy materials for 3D bioprinting since they are abundant and combine adequate physicochemical and biomimetic features for the development of novel bioinks. Thus, this review portrays the most relevant advances in polysaccharide-based hydrogel bioinks for 3D bioprinting, focusing on the last five years, with emphasis on their properties, advantages, and limitations, considering polysaccharide families classified according to their source, namely from seaweed, higher plants, microbial, and animal (particularly crustaceans) origin.

Engineered Ionene/PNIPAM Hybrid Dual-Response Material Generating Tunable and Unique Optical Modes for Adaptive Solar Transmittance Modulation.

A hybrid smart window exhibiting dual chromic response properties based on an ionene/polymer material is successfully engineered. Thermochromic poly(N-isopropylacrylamide) is integrated with an electrochromic viologen-tethered ionene, also acting as an electrolyte, to produce a smart window that can adaptively control solar visible light transmittance in response to multiple stimuli. This new blend allows the formation of unique reversible optical states, namely, "clear", "amber", "cloudy", and "grainy" states, which are passively triggered by environmental temperature and actively induced by external potential or simultaneously by both. This hybrid material shows tunability in terms of its electrochemical and optical properties, switching kinetics, and coloration efficiency and can also achieve a nearly absolute zero-transmissive state. With the material's excellent solubility and film-forming ability, the smart device can be fabricated with much flexibility and ease. Finally, this device has an all-in-one layer configuration, creating a more compact and simplified design. With all these properties combined, the development of a next-generation multifunctional smart window device, which can efficiently control incoming solar light for energy-saving in buildings and also provide visual comfort, is possible.

Peptoids as a Chiral Stationary Phase for Liquid Chromatography: Insights from Molecular Dynamics Simulations.

Peptoids are peptide regioisomers with attractive structural tunability in terms of sequence and three-dimensional arrangement. Peptoids are foreseen to have a great potential for many diverse applications, including their utilization as a chiral stationary phase in chromatography. To achieve chiral recognition, a chiral side chain is required to allow specific interactions with a given enantiomer from a racemic mixture. One of the most studied chiral stationary phases, built with (S)-N-1-phenylethyl (Nspe) units, was shown to be successful in resolving racemic mixtures of binaphthyl derivatives. However, there is currently no description at the atomic scale of the factors favoring its enantioselectivity. Here, we take advantage of steered molecular dynamics simulations to mimic the elution process at the atomic scale and present evidence that the predominantly right-handed helical conformation of Nspe peptoids and their ability to form stronger hydrogen bonds with the (S) enantiomer are responsible for the chiral recognition of the popular chiral probe 2,2'-bihydroxy-1,1'-binaphthyl.

Unraveling interactions of resonances for tunable low frequency bandgap in multiphase metamaterials under applied deformation

Metamaterial with various degrees of bandgap tunability is an emerging area in manipulating elastic wave transmission characteristics for next generation phononic devices. Although several attempts are made employing multi-fields such as magnetic, electric and thermal etc., mechanical deformation based tunable bandgap is a major interest. However, achieving tunability in terms of broadening or terminating the bandgap in locally resonant acoustic metamaterial (LRAM) remains as challenging tasks. In this work, we propose LRAM by integrating a two-dimensionally periodically arranged square unit cells consisting of soft coated hard inclusion embedded in a polymer scaffold. We develop computational framework to simulate the low frequency bandgap of unit cell under external deformation. At first quasi-static analysis of unit cell has been performed to find static displacement field under prescribed deformation. Further, utilizing Bloch-Floquet wave analysis for the periodic unit cell and finite element based numerical scheme, an eigenvalue problem is formulated to predict dispersion response within irreducible Brillouin zone (IBZ). Analyzing the symmetry group of the unit cell under deformed state for a series of loading, we extract the bandgap responses. Moreover, we illustrate tunable bandgap at low frequency regimes for different inclusion shapes and sizes. To correlate extension and suppression of bandgap under the applied deformation, evolution of local resonances are described with vibration mode shapes.

Highly tunable bioactive fiber-reinforced hydrogel for guided bone regeneration

One of the most damaging pathologies that affects the health of both soft and hard tissues around the tooth is periodontitis. Clinically, periodontal tissue destruction has been managed by an integrated approach involving elimination of injured tissues followed by regenerative strategies with bone substitutes and/or barrier membranes. Regrettably, a barrier membrane with predictable mechanical integrity and multifunctional therapeutic features has yet to be established. Herein, we report a fiber-reinforced hydrogel with unprecedented tunability in terms of mechanical competence and therapeutic features by integration of highly porous poly(ε-caprolactone) fibrous mesh(es) with well-controlled 3D architecture into bioactive amorphous magnesium phosphate-laden gelatin methacryloyl hydrogels. The presence of amorphous magnesium phosphate and PCL mesh in the hydrogel can control the mechanical properties and improve the osteogenic ability, opening a tremendous opportunity in guided bone regeneration (GBR). Results demonstrate that the presence of PCL meshes fabricated via melt electrowriting can delay hydrogel degradation preventing soft tissue invasion and providing the mechanical barrier to allow time for slower migrating progenitor cells to participate in bone regeneration due to their ability to differentiate into bone-forming cells. Altogether, our approach offers a platform technology for the development of the next-generation of GBR membranes with tunable mechanical and therapeutic properties to amplify bone regeneration in compromised sites. Statement of SignificanceIn this study, we developed a fiber-reinforced hydrogel platform with unprecedented tunability in terms of mechanical competence and therapeutic features for guided bone regeneration. We successfully integrated highly porous poly(ε-caprolactone) [PCL] mesh(es) into amorphous magnesium phosphate-laden hydrogels. The stiffness of the engineered hydrogel was significantly enhanced, and this reinforcing effect could be modulated by altering the number of PCL meshes and tailoring the AMP concentration. Furthermore, the fiber-reinforced hydrogel showed favorable cellular responses, significantly higher rates of mineralization, upregulation of osteogenic-related genes and bone formation. In sum, these fiber-reinforced membranes in combination with therapeutic agent(s) embedded in the hydrogel offer a robust, highly tunable platform to amplify bone regeneration not only in periodontal defects, but also in other craniomaxillofacial sites.

POM@MOF Hybrids: Synthesis and Applications

The hybrid materials that are created by supporting or incorporating polyoxometalates (POMs) into/onto metal–organic frameworks (MOFs) have a unique set of properties. They combine the strong acidity, oxygen-rich surface, and redox capability of POMs, while overcoming their drawbacks, such as difficult handling, a low surface area, and a high solubility. MOFs are ideal hosts because of their high surface area, long-range ordered structure, and high tunability in terms of the pore size and channels. In some cases, MOFs add an extra dimension to the functionality of hybrids. This review summarizes the recent developments in the field of POM@MOF hybrids. The most common applied synthesis strategies are discussed, together with major applications, such as their use in catalysis (organocatalysis, electrocatalysis, and photocatalysis). The more than 100 papers on this topic have been systematically summarized in a handy table, which covers almost all of the work conducted in this field up to now.

A Dual‐Ligand Porous Coordination Polymer Chemiresistor with Modulated Conductivity and Porosity

AbstractSingle‐ligand‐based electronically conductive porous coordination polymers/metal–organic frameworks (EC‐PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π‐conjugated EC‐MOF containing copper units with mixed trigonal ligands was developed: Cu3(HHTP)(THQ) (HHTP=2,3,6,7,10,11‐hexahydrotriphenylene, THQ=tetrahydroxy‐1,4‐quinone). The modulated conductivity (σ≈2.53×10−5 S cm−1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m2 g−1) of the Cu3(HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor.

A Dual-Ligand Porous Coordination Polymer Chemiresistor with Modulated Conductivity and Porosity.

Single-ligand-based electronically conductive porous coordination polymers/metal-organic frameworks (EC-PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π-conjugated EC-MOF containing copper units with mixed trigonal ligands was developed: Cu3 (HHTP)(THQ) (HHTP=2,3,6,7,10,11-hexahydrotriphenylene, THQ=tetrahydroxy-1,4-quinone). The modulated conductivity (σ≈2.53×10-5 S cm-1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m2 g-1 ) of the Cu3 (HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor.

Gradient-Index Granular Crystals: From Boomerang Motion to Asymmetric Transmission of Waves.

We present a gradient-index crystal that offers extreme tunability in terms of manipulating the propagation of elastic waves. For small-amplitude excitations, we achieve control over wave transmission depth into the crystal. We numerically and experimentally demonstrate a boomeranglike motion of a wave packet injected into the crystal. For large-amplitude excitations on the same crystal, we invoke nonlinear effects. We numerically and experimentally demonstrate asymmetric wave transmission from two opposite ends of the crystal. Such tunable systems can thus inspire a novel class of designed materials to control linear and nonlinear elastic wave propagation in multiscales.

Microporous Metal-Organic Frameworks for Adsorptive Separation of C5-C6 Alkane Isomers.

The separation of alkane isomers, particularly C5-C6 alkanes, is of paramount importance in the petrochemical industry to achieve high quality gasoline. Upon catalytic isomerization reactions, less branched alkanes (with lower octane number) need to be separated from their more branched isomers (with higher octane number) in order to improve the octane rating of gasoline. To reduce the high energy input associated with distillations, the primary separation technique currently used in industry, adsorptive separation by porous solids has been proposed. For example, zeolite 5A has been used as the adsorbent material for adsorptive separation of linear alkanes from their branched isomers, as a supplement technology to distillations. However, due to the limited number of zeolite structures and the lack of porosity tenability in these compounds, the task has not been fully fulfilled by using zeolites. Metal-organic frameworks (MOFs), in light of their structural diversity and high tunability in terms of surface area, pore size, and pore shape, offer new opportunities for resolving industrially relevant separation of alkanes through selective adsorption. This Account summarizes recent development of microporous MOFs for the separation of alkanes, with an emphasis on C5-C6 alkane isomers, including early examples of alkane separation by MOFs, as well as the latest advancement on tailor-made microporous MOFs for size sieving of C5-C6 alkane isomers. The limitation of zeolite 5A as a sorbent material for the separation of C5-C6 alkane isomers lies in its relatively low adsorption capacity. In addition, it is not capable of separating branched alkanes, which is a crucial step for further improving the octane rating of gasoline. The high porosity and tunable pore size and pore shape of MOFs may afford them higher adsorption capacity and selectivity when used for alkane separation. MOFs with pore size slightly larger than the kinetic diameter of branched alkanes can effectively separate alkane isomers through thermodynamically controlled separation, as seen in the case of Fe2(bdp)3 (bdp2- = 1,4-benzenedipyrazolate). This MOF is capable of separating a mixture of hexane isomers by the degrees of branching, with higher adsorption capacity than zeolites under similar conditions but with relatively low selectivity. One effective strategy for obtaining MOFs with optimal pore size and pore shape for highly selective adsorption is to make use of reticular chemistry and precise ligand design. By applying topologically directed design strategy and precisely controlling the pore structure or ligand functionality, we have successfully synthesized a series of highly robust MOFs built on tetratopic carboxylate linkers that demonstrate high performance for the separation of C5-C6 alkane isomers. Zr-bptc (bptc4-= 3,3',5,5'-biphenyltetracarboxylate) adsorbs linear alkanes only and excludes all branched isomers. This size-exclusion mechanism is very similar to that of zeolite 5A. Yet, Zr-bptc has a significantly enhanced adsorption capacity for n-hexane, 70% higher than that of zeolite 5A under identical conditions. Zr-abtc (abtc4- = 3,3',5,5'-azobenzenetetracarboxylate) is capable of discriminating all three C6 alkane isomers via a thermodynamically controlled process, yielding a high separation factor for monobranched over dibranched isomers. MOFs with flexible framework may exhibit unexpected but desired adsorption properties. Ca(H2tcpb) (tcpb4- = 1,2,4,5-tetrakis(4-carboxyphenyl)-benzene) can fully separate binary or ternary mixtures of C5-C6 alkane isomers into pure form through selective molecular sieving as a result of its temperature- and adsorbate-dependent framework flexibility. The intriguing structural properties and exceptional tunability of these MOFs make them promising candidates for industrial implementation of adsorptive separation of alkane isomers.

Real-Time Spectrum Sniffer for Cognitive Radio Based on Rotman Lens Spectrum Decomposer

We introduce the concept of an energy-detection Rotman-lens spectrum decomposer (RLSD) real-time spectrum-sniffer (RTSS) for cognitive radio. Compared to a previously existing RTSS, the RLSD-RTSS offers the advantages of being 1) Based an a simpler and lower-cost purely passive structure, 2) Easier to design and easily amenable to tunability, 3) Of much broader bandwidth, and 4) Of accommodating more channels. The electrical size of the device is electrically larger, but perfectly acceptable in the millimeter-wave frequency range. The proposed RLSD-RTSS is demonstrated theoretically and experimentally, and is shown to support tunability in terms of both bandwidth-resolution and operation band. Given its unique features, this device may find wide applications in 5G UHD and 3-D video systems.

Polymer/graphene oxide (GO) thermoset composites with GO as a crosslinker

Composites have historically been of intense interest due to their potential to replace glass, wood and metal at a fraction of the weight. Of the many choices of fillers, graphene oxide (GO) is generally attractive for its versatility and tunability in terms of surface functionality, size and shape. While the majority of GO has been incorporated into polymers and polymer precursors by physical mixing, this review focuses on research where GO has served as both a property enhancer and multifunctional crosslinker in thermosets. Methods for preparing GO (with and without additional functionalization) and incorporating it appropriately into thermosets are described. A review of characterization techniques, typically applied before and after GO is incorporated into thermosets and analytical methods for confirming important chemical reactions during crosslinking, is also provided. Finally, the resulting composite thermoset properties are surveyed throughout to connect preparation and characterization methods to their potential practical importance.