Conformal Surface Research Articles

Advanced equivalent source methodologies for near-field acoustic holography

The equivalent source method (ESM) based near-field acoustic holography (NAH) has been used successfully in the reconstruction of the acoustical field over arbitrarily shaped vibrating structures from measurements of the pressure field on a nearby conformal surface. In this work we study the use of the ESM dipole and a combined source representation for NAH reconstructions. Using numerically generated data from an elastic spherical shell acoustic response, the studies are focused on the correct positioning and distribution of the source points in relation to the vibrating surface, accuracy over problematic frequencies and spatial aliasing. Finally, we utilize physical data from a vibrating ship-hull structure to validate the proposed ESM reconstructions.

Conformal Titanyl Phosphate Surface Passivation for Enhancing Photocatalytic Activity

A conformal titanyl phosphate passivation with the thickness of ca. 5 nm on the surface of TiO2 nanoparticles for enhancing the photocatalytic degradation of organic pollutants and hydrogen production is described. The phosphate anion species bound to the surface of TiO2 promote the favorable kinetics of photocatalytic activity and influence the catalytic reaction pathway. By using a facile surfactant-assisted sol-gel process, the surface defects of TiO2 associated with deep traps was reduced and passivated by the phosphate anion species to form the titanyl phosphate. The strong bonds between the titanyl phosphate shell and TiO2 core provided a long-term photochemical stability in aqueous electrolytes with enhanced photocatalytic activities. The titanyl phosphate contributed to the production and stabilization of hydroxyl radicals on the surface of photocatalyst, which facilitated the efficient photooxidation of the organic pollutants. Further, enhancing the photocatalytic hydrogen production was achieved by the titanyl phosphate modified TiO2 (TP-TiO2). Consequently, the conformal titanyl phosphate passivation enhanced photocatalytic activity of TiO2. Comparing to the bare TiO2 nanoparticles, approximately two-fold higher photocatalytic H2 production rate was achieved by the TP-TiO2.

Nanoparticle Induced Conformational Switch Between α-Helix and β-Sheet Attenuates Immunogenic Response of MPT63.

Although significant efforts have been devoted to develop nanoparticle-based biopharmaceuticals, it is not understood how protein conformation and nanoparticle surface modulate each other in optimizing the activity and/or toxicity of the biological molecules. This is particularly important for a protein, which can adopt different conformational states separated by a relatively small energy barrier. In this paper, we have studied nanoparticle binding-induced conformational switch from β-sheet to α-helix of MPT63, a small major secreted protein from Mycobacterium tuberculosis and a drug target against Tuberculosis. The binding of magnetite nanoparticles to MPT63 results in a β-sheet to α-helix switch near the sequence stretch between the 19th and 30th amino acids. As a consequence, the immunogenic response of the protein becomes compromised, which could be restored by protein engineering. This study emphasizes that conformational stability toward NP surface binding may require optimization involving genetic engineering for development of a nanoparticle conjugated pharmaceutical.

Autotaxin in Pathophysiology and Pulmonary Fibrosis.

Lysophospholipid signaling is emerging as a druggable regulator of pathophysiological responses, and especially fibrosis, exemplified by the relative ongoing clinical trials in idiopathic pulmonary fibrosis (IPF) patients. In this review, we focus on ectonucleotide pyrophosphatase-phosphodiesterase 2 (ENPP2), or as more widely known Autotaxin (ATX), a secreted lysophospholipase D (lysoPLD) largely responsible for extracellular lysophosphatidic acid (LPA) production. In turn, LPA is a bioactive phospholipid autacoid, forming locally upon increased ATX levels and acting also locally through its receptors, likely guided by ATX's structural conformation and cell surface associations. Increased ATX activity levels have been detected in many inflammatory and fibroproliferative conditions, while genetic and pharmacologic studies have confirmed a pleiotropic participation of ATX/LPA in different processes and disorders. In pulmonary fibrosis, ATX levels rise in the broncheoalveolar fluid (BALF) and stimulate LPA production. LPA engagement of its receptors activate multiple G-protein mediated signal transduction pathways leading to different responses from pulmonary cells including the production of pro-inflammatory signals from stressed epithelial cells, the modulation of endothelial physiology, the activation of TGF signaling and the stimulation of fibroblast accumulation. Genetic or pharmacologic targeting of the ATX/LPA axis attenuated disease development in animal models, thus providing the proof of principle for therapeutic interventions.

Defect-free TiC/Si multi-layer electrical discharge coatings

The process of electrical discharge coating (EDC) may be used to deposit hard materials on conformal substrate surfaces. Next generation EDM'd components may exploit attachment phenomena to enhance recast layer properties, to avoid the need for recast layer removal. Here, a ceramic based composite layer was developed without cracking and porosity for the first time, using sequential coating using sacrificial TiC and Si electrodes. Attenuation of the discharge process by gap widening using Si debris in the gap explained improved layer properties. Composite coatings combining WC and TiC were also demonstrated, with good elemental intermixing. Attachment level was correlated strongly with melting point, with high melting point materials resisting ejection due to more rapid solidification. Nanoindentation showed the TiC and WC/TiC layers possessed the highest mean hardness values, approximately double that of the Cu based machined layer which itself yielded a much higher hardness of 11.0 GPa compared to 1.9 GPa of the substrate.

Beamwidth Control of Omnidirectional Antenna Using Conformal Frequency Selective Surface of Different Curvatures

Development and implementation of different curvatures of a conformal frequency selective surface (FSS) for achieving beam diversity in a dual-band monopole antenna are demonstrated. The FSS based on a flexible dielectric substrate (polymer) is reflective at 3.5 GHz. The curved FSS when incorporated in the antenna gives different beamwidths (3 dB) between 68°–130° for concave shape and 144°–210° for convex shape at 3.5 GHz. In both the cases, omnidirectional radiation from the antenna is maintained at 5.8 GHz. Later, a corner reflector based on the FSS instead of a metal, operating at 5.8 GHz, is integrated in the antenna along with the convex shaped curved FSS. The new antenna system exhibits a beamwidth of 190° with a peak gain of 6.8 dBi at 3.5 GHz and the beamwidth of 58° with a peak gain of 8.3 dBi at 5.8 GHz. The proposed method is useful for achieving beam diversity in multiband antennas. Simulation results from ANSYS HFSS and experimental measurements of the fabricated prototypes are provided.

Conformal Multifunctional Titania Shell on Iron Oxide Nanorod Conversion Electrode Enables High Stability Exceeding 30 000 Cycles in Aqueous Electrolyte

AbstractIron oxide is promising for use in aqueous energy storage devices due to the high capacity, but one of the most challenging problems is cycling instability within the large potential window that results from the complete quasi‐conversion reaction. Herein, a conformal surface coating strategy toward iron oxide via atomic layer deposition (ALD) is presented and an Fe3O4@TiO2 core–shell nanorod array anode is reported that exhibits remarkable cycling performance exceeding 30 000 times within a wide potential window in neutral lithium salt electrolyte. ALD offers a uniform and precisely controllable TiO2 shell that not only buffers the inner volume expansion of Fe3O4, but also contributes extra capacity through Li+ intercalation/de‐intercalation and helps to alleviate the water electrolysis. Furthermore, by pairing with a pseduocapacitive cathode of V2O3@carbon and using a hydrogel electrolyte of PVA‐LiCl, a unique flexible quasi‐solid‐state hybrid supercapacitor can be assembled. With a high voltage of 2.0 V, the device delivers high volumetric energy and power densities (2.23 mWh cm−3, 1090 mW cm−3), surpassing many recently reported flexible supercapacitors. This work highlights the importance of ALD conformal multifunctional shell to instable nanoarray electrodes in aqueous electrolytes and brings new opportunities to design advanced aqueous hybrid energy storage devices.

Plasmonic Biomimetic Nanocomposite with Spontaneous Subwavelength Structuring as Broadband Absorbers

Broadband plasmonic absorbers are essential components for photovoltaic, photothermal, and light-emitting devices. They are often made by lithographic processes that impart out-of-plane surface features with subwavelength dimensions to metallic films. However, lithographic subwavelength patterning of inexpensive plasmonic ceramics, such as TiN, is challenging because of high-temperature processing and the chemical robustness of these materials. In this work, we show that layer-by-layer assembly (LbL) of TiN plasmonic nanoparticles with polyelectrolytes results in spontaneous formation of out-of-plane topography with subwavelength dimensions. The columnar morphology of these corrugated coatings and their plasmonic functionality results in broadband absorption capabilities exemplified by 90% of the light from the ultraviolet to infrared parts of the spectrum being absorbed. The method is applicable to large, flexible, and conformal surfaces with complex geometry. It is also fast, scalable, and environmental...

Polynomial conserved quantities of Lie applicable surfaces

Using the gauge theoretic approach for Lie applicable surfaces, we characterise certain subclasses of surfaces in terms of polynomial conserved quantities. These include isothermic and Guichard surfaces of conformal geometry and L-isothermic surfaces of Laguerre geometry. In this setting one can see that the well known transformations available for these surfaces are induced by the transformations of the underlying Lie applicable surfaces. We also consider linear Weingarten surfaces in this setting and develop a new Bäcklund-type transformation for these surfaces.

Conformal Antireflective Surface Formed onto 3-D Silicon Structure.

This letter reports on the fabrication, simulation and characterization of conformal antireflective black-silicon (BSi) nanowires on a 3D silicon structure. The BSi nanostructures were formed on various facets of a 3D Si structure including sharp tips and sidewalls using a metal-assisted chemical (MAC) etching process. The conformal BSi design was simulated using FDTD Lumerical software. The antireflection capability was indicated by the quantified reduction in normalized intensity after image processing of diffraction patterns. An optical iris of 1.00-mm circular aperture with conformal BSi nanowires was fabricated and characterized to demonstrate the anti-reflectivity capability at two visible wavelengths of 532 and 633 nm. The iris showed a significant reduction in glare around its Airy disc, up to 3× smaller than the same one but without the BSi nanostructures.

Sequence Directionality Dramatically Affects LCST Behavior of Elastin-Like Polypeptides.

Elastin-like polypeptides (ELP) exhibit an inverse temperature transition or lower critical solution temperature (LCST) transition phase behavior in aqueous solutions. In this paper, the thermal responsive properties of the canonical ELP, poly(VPGVG), and its reverse sequence poly(VGPVG) were investigated by turbidity measurements of the cloud point behavior, circular dichroism (CD) measurements, and all-atom molecular dynamics (MD) simulations to gain a molecular understanding of mechanism that controls hysteretic phase behavior. It was shown experimentally that both poly(VPGVG) and poly(VGPVG) undergo a transition from soluble to insoluble in aqueous solution upon heating above the transition temperature ( Tt). However, poly(VPGVG) resolubilizes upon cooling below its Tt, whereas the reverse sequence, poly(VGPVG), remains aggregated despite significant undercooling below the Tt. The results from MD simulations indicated that a change in sequence order results in significant differences in the dynamics of the specific residues, especially valines, which lead to extensive changes in the conformations of VPGVG and VGPVG pentamers and, consequently, dissimilar propensities for secondary structure formation and overall structure of polypeptides. These changes affected the relative hydrophilicities of polypeptides above Tt, where poly(VGPVG) is more hydrophilic than poly(VPGVG) with more extended conformation and larger surface area, which led to formation of strong interchain hydrogen bonds responsible for stabilization of the aggregated phase and the observed thermal hysteresis for poly(VGPVG).

Atomic Layer Deposition of ZnO and Doped ZnO As Alternative Transparent Conducting Oxides for Photovoltaics

Organometallic halide perovskite solar cells have gained considerable interest in recent times, with low cost and high power conversion efficiencies [1]. However, such cells are not without problems such as, stability, scalability and the need for a low thermal budget in the fabrication of tandem structures. In this work, we examine the transparent conducting electrode where the current materials of choice are FTO and ITO which require a higher process temperature (>450oC).Zinc oxide thin films have attracted significant attention as transparent conducting oxides due to their diverse electrical and optical properties. ZnO is an n-type semiconductor with a direct band gap of 3.3 eV. It is optically transparent in the UV/visible and infrared spectra and exhibits promising electrical properties. ALD has distinct characteristics that make it a prospective deposition method of ZnO and doped ZnO, low temperature, conformal and large surface area coating capabilities. The deposition of ZnO and doped ZnO has previously been reported. In this work, an ALD process has been developed to deposit ZnO as a potential TCO in solar cells. ZnO was deposited using low temperature atomic layer deposition (ALD). Subsequently, zinc oxide was doped with Al, Ti and Hf and the electrical, optical and structural properties were analyzed to determine the effect of doping on ZnO. The presented results revealed that Ti-doped ZnO was the suitable TCO candidate with a sheet resistance value of 41 Ω/□ and electron mobility of 12.8 cm2/Vs. In addition to promising electrical properties, Ti-doped ZnO also exhibited high optical transparency of >80% in the UV/ visible and IR ranges. We demonstrate that ALD of Ti-doped ZnO could be a viable alternative to ITO and FTO for TCO materials in photovoltaics. Preliminary data from perovskite solar cells fabricated with a ZnO based transparent conducting electrode are presented and discussed. [1] https://www.nrel.gov/pv/assets/images/efficiency-chart.png

(Invited) Inkjet-Printed Stretchable Electronic Devices, Circuits, Sensors, and Displays

Stretchable electronic systems built on soft substrates offer more conformal surface coverage and better durability than flexible electronics, and have generated significant research interests recently for potential applications in wearable/implantable health monitoring and diagnostic devices, electronic skin for prosthesis or soft robotics, stretchable displays and many more. Nevertheless, the large-area and low-cost fabrication of high-performance intrinsically stretchable electronic devices has remained to be extremely challenging. In this talk, I will present our recent work on addressing the two major challenges faced by stretchable electronics - the development of intrinsically-stretchable electronic materials and the need for scalable fabrication processes. We have developed nanomaterials-based metal, semiconductor, and dielectric materials with superior electronic property, stretchability, and inter-layer adhesion. Such materials are formulated as electronic inks to allow highly uniform and scalable material patterning using a inkjet-printed process, allowing us to achieve intrinsically stretchable thin-film transistors (TFTs) and integrated logic circuits made entirely by printing on ultrathin elastic polydimethylsiloxane (PDMS) substrates. Electrical and mechanical characterizations reveal that the TFTs and logic circuits can withstand up to 100% tensile strain along either channel length or channel width directions for thousands of cycles while showing no noticeable degradation in electrical performance. In addition to the above, I will also present our work on printed stretchable sensors and displays for wearable electronics and soft robotics applications. Our platform may offer a new entry into more sophisticated stretchable electronic systems with monolithically integrated sensors, actuators, and displays, fabricated by scalable and low-cost methods for real-life applications.

Bifunctional Conducting Polymer Coated CoP Core–Shell Nanowires on Carbon Paper as a Free‐Standing Anode for Sodium Ion Batteries

AbstractThis study proposes a conformal surface coating of conducting polymer for protecting 1D nanostructured electrode material, thereby enabling a free‐standing electrode without binder for sodium ion batteries. Here, polypyrrole (PPy), which is one of the representative conducting polymers, encapsulated cobalt phosphide (CoP) nanowires (NWs) grown on carbon paper (CP), finally realizes 1D core–shell CoP@PPy NWs/CP. The CoP core is connected to the PPy shell via strong chemical bonding, which can maintain a Co–PPy framework during charge/discharge. It also possesses bifunctional features that enhances the charge transfer and buffers the volume expansion. Consequently, 1D core–shell CoP@PPy NWs/CP demonstrates superb electrochemical performance, delivering a high areal capacity of 0.521 mA h cm−2 at 0.15 mA cm−2 after 100 cycles, and 0.443 mA h cm−2 at 1.5 mA cm−2 even after 1000 cycles. Even at a high current density of 3 mA cm−2, a significant areal discharge capacity reaching 0.285 mA h cm−2 is still maintained. The outstanding performance of the CoP@PPy NWs/CP free‐standing anode provides not only a novel insight into the modulated volume expansion of anode materials but also one of the most effective strategies for binder‐free and free‐standing electrodes with decent mechanical endurance for future secondary batteries.

Structure of the basement surface and sediments in the Kochkor basin (Tien Shan): geological and geophysical evidence

The basement surface and sediments of the Kochkor basin have been studied by structural geological and geophysical methods. The work included high-resolution mapping of the southern basin margin, with a focus on Cenozoic basin stratigraphy, structural unconformities, basement/sediment contacts, and latest deformation (folds, fractures, and faults). Magnetotelluric (MT) soundings provided insights into basin and basement structure, especially important in the poorly exposed eastern flank of the basin margin. The sections across the southern margin of the basin based on geological and geophysical data reveal deformation in both the basement and the sediments. Deformation in sediments shows up as folding, conformal peneplain surfaces, large faults, low-angle detachment faults, and related thrust-fold belts. Thrusting in sediments is inferred to result from cataclastic flow and mass redistribution in disintegrated basement granites. With this mechanism, the total amount of thrusting in the central part of the basin can exceed the convergence of the basin sides.

Grain Boundary Conformed Volumetric Mesh Generation from a Three-Dimensional Voxellated Polycrystalline Microstructure

We present a new comprehensive scheme for generating grain boundary conformed, volumetric mesh elements from a three-dimensional voxellated polycrystalline microstructure. From the voxellated image of a polycrystalline microstructure obtained from the Monte Carlo Potts model in the context of isotropic normal grain growth simulation, its grain boundary network is approximated as a curvature-maintained conformal triangular surface mesh using a set of in-house codes. In order to improve the surface mesh quality and to adjust mesh resolution, various re-meshing techniques in a commercial software are applied to the approximated grain boundary mesh. It is found that the aspect ratio, the minimum angle and the Jacobian value of the re-meshed surface triangular mesh are successfully improved. Using such an enhanced surface mesh, conformal volumetric tetrahedral elements of the polycrystalline microstructure are created using a commercial software, again. The resultant mesh seamlessly retains the short- and long-range curvature of grain boundaries and junctions as well as the realistic morphology of the grains inside the polycrystal. It is noted that the proposed scheme is the first to successfully generate three-dimensional mesh elements for polycrystals with high enough quality to be used for the microstructure-based finite element analysis, while the realistic characteristics of grain boundaries and grains are maintained from the corresponding voxellated microstructure image.

Large scale Full QM-MD investigation of small peptides and insulin adsorption on ideal and defective TiO2 (1 0 0) surfaces. Influence of peptide size on interfacial bonds

Large biomolecule interaction with oxide surface has attracted a lot of attention because it drives behavior of implanted devices in the living body. To investigate the role of TiO2 surface structure on a large polypeptide (insulin) adsorption, we use a homemade mixed Molecular Dynamics-Full large scale Quantum Mechanics code. A specific re-parameterized (Ti) and globally convergent NDDO method fitted on high level ab initio method (coupled cluster CCSD(T) and DFT) allows us to safely describe the electronic structure of the whole insulin-TiO2 surface system (up to 4000 atoms). Looking specifically at carboxylate residues, we demonstrate in this work that specific interfacial bonds are obtained from the insulin/TiO2 system that are not observed in the case of smaller peptides (tripeptides, insulin segment chains with different configurations). We also demonstrate that a large part of the adsorption energy is compensated by insulin conformational energy changes and surface defects enhanced this trend. Large slab dimensions allow us to take into account surface defects that are actually beyond ab initio capabilities owing to size effect. These results highlight the influence of the surface structure on the conformation and therefore of the possible inactivity of an adsorbed polypeptides.

Overview of printing wearable antenna

The usage of wearable textiles in antenna section has been seen increased due to the advanced in miniaturization of wireless devices. A wearable antenna is meant to be a part of the clothing and body used for communication purposes, which includes tracking and navigation, mobile computing and public safety. Printing of conductive ink gives the leisure of flexibility properties on electronics thus allowing it to be used on conformal surfaces such as textiles. However, the current printing techniques mostly suffer from ink incompatibility and limited of substrates to be printed with. Hence, this paper discusses an overview of conventional and current printing techniques of wearable antenna and a potential of automatic syringe deposition system to print electronics structure mainly antenna using conductive ink on conformal substrates particularly textiles.

Identification of Rare Lewis Oligosaccharide Conformers in Aqueous Solution Using Enhanced Sampling Molecular Dynamics.

Determining the conformations accessible to carbohydrate ligands in aqueous solution is important for understanding their biological action. In this work, we evaluate the conformational free-energy surfaces of Lewis oligosaccharides in explicit aqueous solvent using a multidimensional variant of the swarm-enhanced sampling molecular dynamics (msesMD) method; we compare with multi-microsecond unbiased MD simulations, umbrella sampling, and accelerated MD approaches. For the sialyl Lewis A tetrasaccharide, msesMD simulations in aqueous solution predict conformer landscapes in general agreement with the other biased methods and with triplicate unbiased 10 μs trajectories; these simulations find a predominance of closed conformer and a range of low-occupancy open forms. The msesMD simulations also suggest closed-to-open transitions in the tetrasaccharide are facilitated by changes in ring puckering of its GlcNAc residue away from the 4C1 form, in line with previous work. For sialyl Lewis X tetrasaccharide, msesMD simulations predict a minor population of an open form in solution corresponding to a rare lectin-bound pose observed crystallographically. Overall, from comparison with biased MD calculations, we find that triplicate 10 μs unbiased MD simulations may not be enough to fully sample glycan conformations in aqueous solution. However, the computational efficiency and intuitive approach of the msesMD method suggest potential for its application in glycomics as a tool for analysis of oligosaccharide conformation.

Prediction of the Crystal Morphology of β-HMX using a Generalized Interfacial Structure Analysis Model

At sufficiently low supersaturations such that the spiral growth mechanism dominates, β-cyclotetramethylenetetranitramine (HMX) grows from acetone into a polyhedron surrounded mainly by the (020) and (011) faces. In order to elucidate the morphology, a generalized form of the interfacial structure analysis model is suggested. In this method, the molecular order parameters of crystals are defined to identify the orientation and conformation of the adsorbed growth unit at the interface. This presents a robust method to calculate the orientational and conformational free energy surfaces that are utilized for the spiral growth model of centrosymmetric growth units with polygonal spiral edges. From the metadynamics simulation using these order parameters as collective variables, the free energy surfaces with respect to the collective variables revealed that high conformational free energy of the chair conformation discouraged preordering of the growth units into crystal-like orientation and conformation. The r...