Showing papers by "Wright-Patterson Air Force Base published in 2018"

Accelerating the discovery of materials for clean energy in the era of smart automation

Abstract: The discovery and development of novel materials in the field of energy are essential to accelerate the transition to a low-carbon economy. Bringing recent technological innovations in automation, robotics and computer science together with current approaches in chemistry, materials synthesis and characterization will act as a catalyst for revolutionizing traditional research and development in both industry and academia. This Perspective provides a vision for an integrated artificial intelligence approach towards autonomous materials discovery, which, in our opinion, will emerge within the next 5 to 10 years. The approach we discuss requires the integration of the following tools, which have already seen substantial development to date: high-throughput virtual screening, automated synthesis planning, automated laboratories and machine learning algorithms. In addition to reducing the time to deployment of new materials by an order of magnitude, this integrated approach is expected to lower the cost associated with the initial discovery. Thus, the price of the final products (for example, solar panels, batteries and electric vehicles) will also decrease. This in turn will enable industries and governments to meet more ambitious targets in terms of reducing greenhouse gas emissions at a faster pace. The discovery and development of advanced materials are imperative for the clean energy sector. We envision that a closed-loop approach, which combines high-throughput computation, artificial intelligence and advanced robotics, will sizeably reduce the time to deployment and the costs associated with materials development.

3D Printing of Liquid Crystal Elastomeric Actuators with Spatially Programed Nematic Order.

Abstract: Liquid crystal elastomers (LCEs) are soft materials capable of large, reversible shape changes, which may find potential application as artificial muscles, soft robots, and dynamic functional architectures. Here, the design and additive manufacturing of LCE actuators (LCEAs) with spatially programed nematic order that exhibit large, reversible, and repeatable contraction with high specific work capacity are reported. First, a photopolymerizable, solvent-free, main-chain LCE ink is created via aza-Michael addition with the appropriate viscoelastic properties for 3D printing. Next, high operating temperature direct ink writing of LCE inks is used to align their mesogen domains along the direction of the print path. To demonstrate the power of this additive manufacturing approach, shape-morphing LCEA architectures are fabricated, which undergo reversible planar-to-3D and 3D-to-3D' transformations on demand, that can lift significantly more weight than other LCEAs reported to date.

Carbon Nanotubes and Related Nanomaterials: Critical Advances and Challenges for Synthesis toward Mainstream Commercial Applications

Abstract: Advances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications. While the primary focus of this review is on the science framework of SWCNT growth, we draw connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene.

Demonstration of high mobility and quantum transport in modulation-doped β-(AlxGa1-x)2O3/Ga2O3 heterostructures

Abstract: In this work, we demonstrate a high mobility two-dimensional electron gas (2DEG) formed at the β-(AlxGa1-x)2O3/Ga2O3 interface through modulation doping. Shubnikov-de Haas (SdH) oscillations were observed in the modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure, indicating a high-quality electron channel formed at the heterojunction interface. The formation of the 2DEG channel was further confirmed by the weak temperature dependence of the carrier density, and the peak low temperature mobility was found to be 2790 cm2/Vs, which is significantly higher than that achieved in bulk-doped Beta-phase Gallium Oxide (β-Ga2O3). The observed SdH oscillations allowed for the extraction of the electron effective mass in the (010) plane to be 0.313 ± 0.015 m0 and the quantum scattering time to be 0.33 ps at 3.5 K. The demonstrated modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure lays the foundation for future exploration of quantum physical phenomena and semiconductor device technologies based on the β-Ga2O3 material system.

Recent Progress on Stability and Passivation of Black Phosphorus.

Abstract: From a fundamental science perspective, black phosphorus (BP) is a canonical example of a material that possesses fascinating surface and electronic properties. It has extraordinary in-plane anisotropic electrical, optical, and vibrational states, as well as a tunable band gap. However, instability of the surface due to chemical degradation in ambient conditions remains a major impediment to its prospective applications. Early studies were limited by the degradation of black phosphorous surfaces in air. Recently, several robust strategies have been developed to mitigate these issues, and these novel developments can potentially allow researchers to exploit the extraordinary properties of this material and devices made out of it. Here, the fundamental chemistry of BP degradation and the tremendous progress made to address this issue are extensively reviewed. Device performances of encapsulated BP are also compared with nonencapsulated BP. In addition, BP possesses sensitive anisotropic photophysical surface properties such as excitons, surface plasmons/phonons, and topologically protected and Dirac semi-metallic surface states. Ambient degradation as well as any passivation method used to protect the surface could affect the intrinsic surface properties of BP. These properties and the extent of their modifications by both the degradation and passivation are reviewed.

Random heteropolymers preserve protein function in foreign environments

Abstract: The successful incorporation of active proteins into synthetic polymers could lead to a new class of materials with functions found only in living systems. However, proteins rarely function under the conditions suitable for polymer processing. On the basis of an analysis of trends in protein sequences and characteristic chemical patterns on protein surfaces, we designed four-monomer random heteropolymers to mimic intrinsically disordered proteins for protein solubilization and stabilization in non-native environments. The heteropolymers, with optimized composition and statistical monomer distribution, enable cell-free synthesis of membrane proteins with proper protein folding for transport and enzyme-containing plastics for toxin bioremediation. Controlling the statistical monomer distribution in a heteropolymer, rather than the specific monomer sequence, affords a new strategy to interface with biological systems for protein-based biomaterials.

GST-on-silicon hybrid nanophotonic integrated circuits: a non-volatile quasi-continuously reprogrammable platform

Abstract: Reconfiguration of silicon photonic integrated circuits relying on the weak, volatile thermo-optic or electro-optic effect of silicon usually suffers from a large footprint and energy consumption. Here, integrating a phase-change material, Ge2Sb2Te5 (GST) with silicon microring resonators, we demonstrate an energy-efficient, compact, non-volatile, reprogrammable platform. By adjusting the energy and number of free-space laser pulses applied to the GST, we characterize the strong broadband attenuation and optical phase modulation effects of the platform, and perform quasi-continuous tuning enabled by thermo-optically-induced phase changes. As a result, a non-volatile optical switch with a high extinction ratio, as large as 33 dB, is demonstrated.

Layered liquid crystal elastomer actuators.

Abstract: Liquid crystalline elastomers (LCEs) are soft, anisotropic materials that exhibit large shape transformations when subjected to various stimuli. Here we demonstrate a facile approach to enhance the out-of-plane work capacity of these materials by an order of magnitude, to nearly 20 J/kg. The enhancement in force output is enabled by the development of a room temperature polymerizable composition used both to prepare individual films, organized via directed self-assembly to retain arrays of topological defect profiles, as well as act as an adhesive to combine the LCE layers. The material actuator is shown to displace a load >2500× heavier than its own weight nearly 0.5 mm.

Teaming With a Synthetic Teammate: Insights into Human-Autonomy Teaming:

Abstract: ObjectiveThree different team configurations are compared with the goal of better understanding human-autonomy teaming (HAT).BackgroundAlthough an extensive literature on human-automation interacti...

High-Temperature and High-Energy-Density Dipolar Glass Polymers Based on Sulfonylated Poly(2,6-dimethyl-1,4-phenylene oxide).

Abstract: A new class of high-temperature dipolar polymers based on sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) (SO2 -PPO) was synthesized by post-polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (Tg ≈220 °C), the dipolar polarization of these SO2 -PPOs was enhanced, and thus the dielectric constant was high. Consequently, the discharge energy density reached up to 22 J cm-3 . Owing to its high Tg , the SO2 -PPO25 sample also exhibited a low dielectric loss. For example, the dissipation factor (tan δ) was 0.003, and the discharge efficiency at 800 MV m-1 was 92 %. Therefore, these dipolar glass polymers are promising for high-temperature, high-energy-density, and low-loss electrical energy storage applications.

Intestinal in vitro and ex vivo Models to Study Host-Microbiome Interactions and Acute Stressors.

Abstract: The gut microbiome is extremely important for maintaining homeostasis with host intestinal epithelial, neuronal, and immune cells and this host-microbe interaction is critical during times of stress or disease. Environmental, nutritional, and cognitive stress are just a few factors known to influence the gut microbiota and are thought to induce microbial dysbiosis. Research on this bidirectional relationship as it pertains to health and disease is extensive and rapidly expanding in both in vivo and in vitro/ex vivo models. However, far less work has been devoted to studying effects of host-microbe interactions on acute stressors and performance, the underlying mechanisms, and the modulatory effects of different stressors on both the host and the microbiome. Additionally, the use of in vitro/ex vivo models to study the gut microbiome and human performance has not been researched extensively nor reviewed. Therefore, this review aims to examine current evidence concerning the current status of in vitro and ex vivo host models, the impact of acute stressors on gut physiology/microbiota as well as potential impacts on human performance and how we can parlay this information for DoD relevance as well as the broader scientific community. Models reviewed include widely utilized intestinal cell models from human and animal models that have been applied in the past for stress or microbiology research as well as ex vivo organ/tissue culture models and new innovative models including organ-on-a-chip and co-culture models.

Analysis of Dynamic Stall on a Pitching Airfoil Using High-Fidelity Large-Eddy Simulations

Abstract: The onset of unsteady separation and dynamic stall vortex formation over a constant-rate pitching airfoil is analyzed by means of high-fidelity large-eddy simulations. The flowfields are computed b...

Anderson light localization in biological nanostructures of native silk

Abstract: Light in biological media is known as freely diffusing because interference is negligible. Here, we show Anderson light localization in quasi-two-dimensional protein nanostructures produced by silkworms (Bombyx mori). For transmission channels in native silk, the light flux is governed by a few localized modes. Relative spatial fluctuations in transmission quantities are proximal to the Anderson regime. The sizes of passive cavities (smaller than a single fibre) and the statistics of modes (decomposed from excitation at the gain–loss equilibrium) differentiate silk from other diffusive structures sharing microscopic morphological similarity. Because the strong reflectivity from Anderson localization is combined with the high emissivity of the biomolecules in infra-red radiation, silk radiates heat more than it absorbs for passive cooling. This collective evidence explains how a silkworm designs a nanoarchitectured optical window of resonant tunnelling in the physically closed structures, while suppressing most of transmission in the visible spectrum and emitting thermal radiation. Light in biological media is known as freely diffusing because interference is negligible. Here, the authors demonstrate Anderson localization of light from quasi-two-dimensional nanostructures in silk fibres.

Strain-induced high-temperature perovskite ferromagnetic insulator

Abstract: Ferromagnetic insulators are required for many new magnetic devices, such as dissipationless quantum-spintronic devices, magnetic tunneling junctions, etc. Ferromagnetic insulators with a high Curie temperature and a high-symmetry structure are critical integration with common single-crystalline oxide films or substrates. So far, the commonly used ferromagnetic insulators mostly possess low-symmetry structures associated with a poor growth quality and widespread properties. The few known high-symmetry materials either have extremely low Curie temperatures (≤16 K), or require chemical doping of an otherwise antiferromagnetic matrix. Here we present compelling evidence that the LaCoO3 single-crystalline thin film under tensile strain is a rare undoped perovskite ferromagnetic insulator with a remarkably high TC of up to 90 K. Both experiments and first-principles calculations demonstrate tensile-strain-induced ferromagnetism which does not exist in bulk LaCoO3 The ferromagnetism is strongest within a nearly stoichiometric structure, disappearing when the Co2+ defect concentration reaches about 10%. Significant impact of the research includes demonstration of a strain-induced high-temperature ferromagnetic insulator, successful elevation of the transition over the liquid-nitrogen temperature, and high potential for integration into large-area device fabrication processes.

Mid-infrared supercontinuum generation from 1.6 to >11 μm using concatenated step-index fluoride and chalcogenide fibers.

Abstract: We demonstrate an all-fiber supercontinuum source that generates a continuous spectrum from 1.6 μm to >11 μm with 417 mW on-time average power at 33% duty cycle. By utilizing a master oscillator power amplifier pump with three amplification stages and concatenating solid core ZBLAN, arsenic sulfide, and arsenic selenide fibers, we shift 1550 nm light to ∼4.5 μm, ∼6.5 μm, and >11 μm, respectively. With 69 mW past 7.5 μm, this source provides both high power and broad spectral expansion, while outputting a single fundamental mode.

Large-Area Lasing and Multicolor Perovskite Quantum Dot Patterns

Abstract: DOI: 10.1002/adom.201800474 passivation to achieve high quantum yield due to the self-passivation effect of halogen,[5,6] enabling a facile synthesis of highly fluorescent emitters without the need of careful design of core/shell interface.[7,8] In addition, the absorption and emission spectra of QDs can be altered not only by size but also by the facile composition tuning via anion (i.e., X) exchange, thereby providing more freedom to achieve superior optical properties.[9] Moreover, high net optical gain value of 450 cm−1 and low pump threshold down to 5 μJ cm−2 have been reported, demonstrating that these QDs can be readily used for light amplification and lasing at very low excitation intensity.[10] These properties have been extensively studied for use in spectrochemical probes, light-emitting diodes, and vertical cavity surface emitting lasers. Clearly, these show that CsPbX3 QDs have potential for a variety of optoelectronic applications.[11–13] In recent years, patterning techniques for single crystal and polycrystalline perovskite materials have been extensively developed including electron beam lithography, controlled crystallization via molding, inkjet printing, and template-assisted patterning with intriguing photonic properties.[14–19] In contrast, nearly all studies of perovskite nanoparticles such as QDs to date have focused on the synthesis, photophysics, and optoelectronic applications while the development of patterning techniques has been comparatively few and limited in scope.[20,21] This approach contrasts sharply to the Cd-based QDs where high-resolution lithographic methods such as electron-beam lithography and photolithography have been adopted widely to integrate Cd-based QDs into microand nanoscale devices.[22,23] The difference is essentially understandable, when considering the ionic nature of CsPbX3 QDs, which makes them prone to dissolution in common polar solvents that are required in these high-resolution lithographic methods.[19,24] The chemical instability to polar solvents severely hinders the integration of these QDs into patterned photonic structures. Moreover, unlike counterpart of the bulk perovskite materials that can be patterned by dissolving polymer spheres or templates with nonpolar solvent such as toluene,[19] the ligand-capped perovskite QDs are unfortunately well dispersed in nonpolar solvents. The solvent constraint in both polar and nonpolar solvents indeed places the development of CsPbX3 QD patterning for miniaturized optical arrays in a dilemma. Clearly, a novel lithographic Herein, a novel orthogonal lithography process is reported to pattern all-inorganic perovskite CsPbX3 (X = Cl, Br, I) quantum dot (QD) arrays which cannot be patterned with traditional approaches. This approach involves a combination of fluorinated polymer and solvent to resolve issues of polar–nonpolar solvent constraints thus enabling the fabrication of complex patterns with high optical gain and multicolor emission. This approach is utilized to fabricate high-resolution large-area arrays of microdisk lasers and multicolor (binary and ternary emission) pixels. The optical cavity modes of CsPbBr3 QD microdisk lasers are readily controlled by tuning the disk size, where the mode spacing decreases while the number of modes increases with increasing disk diameter. Finally, the versatility of this approach for the integration of environmentally sensitive QDs with different emission signatures and composition on the same chip, while achieving high-density, high-resolution large-area QD arrays with multicolor pixels, is demonstrated.

Opioid Stewardship in Otolaryngology: State of the Art Review.

Abstract: Objective The United States is facing an epidemic of opioid addiction. Deaths from opioid overdose have quadrupled in the past 15 years and now surpass annual deaths during the height of the human immunodeficiency virus epidemic. There is a link between opioid prescriptions after surgery, opioid misuse, opioid diversion, and use of other drugs of abuse. As surgeons, otolaryngologists contribute to this crisis. Our objective is to outline the risk of abuse from opioids in the management of acute postoperative pain in otolaryngology-head and neck surgery (OHNS) and strategies to avoid misuse. Data Sources PubMed/MEDLINE. Review Methods We conducted a review of the literature on the rate of opioid abuse after surgery, methods of safe opioid use, and strategies to minimize the dangers of opioids. Conclusions Otolaryngologists have a responsibility to treat pain. This begins preoperatively by discussing perioperative pain control and developing a personalized pain control plan. Patients should be aware that opioids carry significant risks of adverse events and abuse. Perioperative use of multimodal nonopioid agents enables pain control and avoidance of opioids in many otolaryngologic cases. When this approach is inadequate, opioids should be used in short duration under close surveillance. Institutional standards for opioid prescribing after common procedures can minimize misuse. Implications for Practice Otolaryngologists need to acknowledge the potential harm that opioids cause. It is essential that we evaluate our practices to ensure that opioids are used responsibly. Furthermore, opioid stewardship should become a priority in otolaryngology.

Metal–Organic Framework Encapsulation for the Preservation and Photothermal Enhancement of Enzyme Activity

Abstract: Interfacing biomolecules with functional materials is a key strategy toward achieving externally-triggered biological function. The rational integration of functional proteins, such as enzymes, with plasmonic nanostructures that exhibit unique optical properties such as photothermal effect provides a means to externally control the enzyme activity. However, due to the labile nature of enzymes, the photothermal effect of plasmonic nanostructures is mostly utilized for the enhancement of the biocatalytic activity of thermophilic enzymes. In order to extend and utilize the photothermal effect to a broader class of enzymes, a means to stabilize the immobilized active protein is essential. Inspired by biomineralization for the encapsulation of soft tissue within protective exteriors in nature, metal-organic framework is utilized to stabilize the enzyme. This strategy provides an effective route to enhance and externally modulate the biocatalytic activity of enzymes bound to functional nanostructures over a broad range of operating environments that are otherwise hostile to the biomolecules.

Curvature by design and on demand in liquid crystal elastomers.

Abstract: The shape of liquid crystalline elastomers (LCEs) with spatial variation in the director orientation can be transformed by exposure to a stimulus. Here, informed by previously reported analytical treatments, we prepare complex spiral patterns imprinted into LCEs and quantify the resulting shape transformation. Quantification of the stimuli-induced shapes reveals good agreement between predicted and experimentally observed curvatures. We conclude this communication by reporting a design strategy to allow LCE films to be anchored at their external boundaries onto rigid substrates without incurring internal, mechanical-mismatch stresses upon actuation, a critical advance to the realization of shape transformation of LCEs in practical device applications.

Characterization of magnetomechanical properties in FeGaB thin films

Abstract: Layered magnetic/piezoelectric heterostructures have drawn a great amount of interest for their potential use in ultra-sensitive magnetoelectric (ME) sensors, ME antennas, voltage tunable inductors, magnetic tunable resonators, etc. It is critically important to characterize the saturation magnetostriction, piezomagnetic coefficient, ΔE effect, and magnetomechanical coupling factor of magnetic thin films, which determine the performance of these ME devices. In this work, a sensitive system has been developed to measure these magnetomechanical properties, on which several different magnetostrictive thin films on the silicon substrate cantilever were characterized. A 0.015 ppm limit of detection of the magnetostriction tester and a frequency resolution of 0.01 Hz of the ΔE tester have been achieved. After magnetic anneal treatment, a record high piezomagnetic coefficient of 12 ppm/Oe, a giant magnetic field induced Young's modulus change of 153 GPa, and a high effective magnetomechanical coupling factor of 0.84 have been measured in FeGaB thin films.

Robust Chiral Organization of Cellulose Nanocrystals in Capillary Confinement.

Abstract: We showed large area uniformly aligned chiral photonic bioderived films from a liquid crystal phase formed by a cellulose nanocrystal (CNC) suspension placed in a thin capillary. As a result of the spatial confinement of the drying process, the interface between coexisting isotropic and chiral phases aligns perpendicular to the long axis of the capillary. This orientation facilitates a fast homogeneous growth of chiral pseudolayers parallel to the interface. Overall, the formation of organized solids takes hours vs weeks in contrast to the slow and heterogeneous process of drying from the traditional dish-cast approach. The saturation of water vapor in one end of the capillary causes anisotropic drying and promotes unidirectional propagation of the anisotropic phase in large regions that results in chiral CNC solid films with a uniformly oriented layered morphology. Corresponding ordering processes were monitored in situ at a nanoscale, mesoscale, and microscopic scale with complementary scattering and microscopic techniques. The resulting films show high orientation order at a multilength scale over large regions and preserved chiral handedness causing a narrower optical reflectance band and uniform birefringence over macroscopic regions in contrast to traditional dish-cast CNC films and those assembled in a magnetic field and on porous substrates. These thin films with a controllable and well-identified uniform morphology, structural colors, and handedness open up interesting possibilities for broad applications in bioderived photonic nanomaterials.

Locally Controlled Cu-Ion Transport in Layered Ferroelectric CuInP2S6

Abstract: Metal thiophosphates are attracting growing attention in the context of quasi-two-dimensional van der Waals functional materials. Alkali thiophosphates are investigated as ion conductors for solid ...

Exploration of High-Frequency Control of Dynamic Stall Using Large-Eddy Simulations

Abstract: Dynamic stall represents a challenge in a number of engineering applications including rotorcraft, maneuvering aircraft, gust encounters, and wind turbines. Delay of the onset of dynamic stall and ...

Molecular Modeling of Cross-Linked Polymers with Complex Cure Pathways: A Case Study of Bismaleimide Resins

Abstract: To date, molecular modeling of cross-linking polymers has focused on those involving single-reaction cure mechanisms, such as epoxies and the epoxide–amine reaction. In this work, we have developed a novel cross-linking framework that is capable of undertaking complex cure mechanisms involving several simultaneous reaction pathways with minimal user input. As a case study, a bismaleimide (BMI) resin is considered herein which possesses multiple cure reactions and reaction pathways. Using an adaptable molecular dynamics simulation method, we highlight our framework by implementing five distinct cure reactions of Matrimid-5292 (a BMI resin) and predicting the corresponding thermomechanical properties. The method is used to establish the influence of different cure reactions and extent of curing on mass density, glass transition temperature, coefficient of thermal expansion, elastic moduli, and thermal conductivity. The developed method is further validated by comparison of these properties to experimentally...

Cesarean Scar Ectopic Pregnancy: Current Management Strategies

Abstract: ImportanceCesarean scar ectopic pregnancy (CSEP) has a high rate of morbidity with nonspecific signs and symptoms making identification difficult. The criterion-standard treatment of CSEP has been subject to debate.ObjectiveThis review defines CSEP, discusses pathogenesis and diagnosis, and compares

MEMS Reconfigurable Broadband Patch Antenna for Conformal Applications

Abstract: An MEMS reconfigurable broadband pixelated patch antenna is introduced for conformal applications, such as in aircrafts or vehicles. The proposed design considers structural fiberglass composite, Rohacell foam, structural epoxy, ultrathin graphite fibers, and conductive epoxy to be the materials of choice. A nonconventional method of MEMS switch installation is developed and used, which requires connecting the MEMS chips to the antenna or feed traces using very small amounts of conductive epoxy and then curing the specimen in an oven. The proposed fabrication and assembly process is a low temperature process and is not limited in terms of specimen size. The proposed reconfigurable antenna has three reconfiguration states that allow it to operate from 1.13 to 1.7 GHz with 3–7 dBi gain, excellent radiation patterns, and low cross polarization.

Stretchable Optomechanical Fiber Sensors for Pressure Determination in Compressive Medical Textiles.

Abstract: Medical textiles are widely used to exert pressure on human tissues during treatment of post-surgical hematoma, burn-related wounds, chronic venous ulceration, and other maladies. However, the inability to dynamically sense and adjust the applied pressure often leads to suboptimal pressure application, prolonging treatment or resulting in poor patient outcomes. Here, a simple strategy for measuring sub-bandage pressure by integrating stretchable optomechanical fibers into elastic bandages is demonstrated. Specifically, these fibers possess an elastomeric photonic multilayer cladding that surrounds an extruded stretchable core filament. They can sustain repetitive strains of over 100%, and respond to deformation with a predictable and reversible color variation. Integrated into elastic textiles, which apply pressure as a function of their strain, these fibers can provide instantaneous and localized pressure feedback. These colorimetric fiber sensors are well suited for medical textiles, athletic apparel, and other smart wearable technologies, especially when repetitive, large deformations are required.