Size Of Wrinkles Research Articles

Successively Controlling Nanoscale Wrinkles of Ultrathin 2D Metal-Organic Frameworks Nanosheets.

The wrinkles are pervasive in ultrathin two-dimensional (2D) materials, but the regulation of wrinkles is rarely explored systematically. Here, we employed a series of carboxylic acids (from formic acid to octanoic acid) to control the wrinkles of Zr-BTB (BTB=1, 3, 5-(4-carboxylphenyl)-benzene) metal-organic framework (MOF) nanosheet. The wrinkles at the micrometer scale were observed with transmission electron microscopy. Furthermore, high-angle annular dark-field (HAADF) images showed lattice distortion in many nanoscale regions, which was precisely matched to the nano-wrinkles. With the changes of hydrophilicity/hydrophobicity, MOF-MOF and MOF-solvent interactions were possibly synergistically regulated and wrinkles with different sizes were obtained, which was supported by HAADF, molecular dynamics, and density functional theory calculation. Different wrinkle sizes resulted in different pore sizes between the Zr-BTB nanosheet interlayers, providing highly-oriented thin films and the successive optimization of kinetic diffusion pathways, proved by grazing-incidence wide-angle X-ray scattering and nitrogen adsorption. The most suitable wrinkle pore from Zr-BTB-C4 exhibited highly efficient chromatographic separation of the substituted benzene isomers. Our work provides a rational route for the modulation of nanoscale wrinkles and their stacked pores of MOF nanosheets and improves the separation abilities of MOFs.

Dry and wet wrinkling of a silk fibroin biopolymer by a shape-memory material with insight into mechanical effects on secondary structures in the silk network.

Surface wrinkling provides an approach to modify the surfaces of biomedical devices to better mimic features of the extracellular matrix and guide cell attachment, proliferation, and differentiation. Biopolymer wrinkling on active materials holds promise but is poorly explored. Here we report a mechanically actuated assembly process to generate uniaxial micro-and nanosized silk fibroin (SF) wrinkles on a thermo-responsive shape-memory polymer (SMP) substrate, with wrinkling demonstrated under both dry and hydrated (cell compatible) conditions. By systematically investigating the influence of SMP programmed strain magnitude, film thickness, and aqueous media on wrinkle stability and morphology, we reveal how to control the wrinkle sizes on the micron and sub-micron length scale. Furthermore, as a parameter fundamental to SMPs, we demonstrate that the temperature during the recovery process can also affect the wrinkle characteristics and the secondary structures in the silk network. We find that with increasing SMP programmed strain magnitude, silk wrinkled topographies with increasing wavelengths and amplitudes are achieved. Furthermore, silk wrinkling is found to increase β-sheet content, with spectroscopic analysis suggesting that the effect may be due primarily to tensile (e.g., Poisson effect and high-curvature wrinkle) loading modes in the SF, despite the compressive bulk deformation (uniaxial contraction) used to produce wrinkles. Silk wrinkles fabricated from sufficiently thick films (roughly 250 nm) persist after 24 h in cell culture medium. Using a fibroblast cell line, analysis of cellular response to the wrinkled topographies reveals high viability and attachment. These findings demonstrate use of wrinkled SF films under physiologically relevant conditions and suggest the potential for biopolymer wrinkles on biomaterials surfaces to find application in cell mechanobiology, wound healing, and tissue engineering.

An embedded digital element model to simulate the wrinkle defects driven by the consolidation of composites

Understanding the mechanisms of fiber wrinkling during the compaction process is of paramount importance as fiber wrinkling significantly affects the mechanical properties of composite materials. This study introduces an embedded digital element model for simulating the consolidation process of prepreg. Flexible digital element chains are employed to simulate the reinforcing effect of fibers on resin, accounting for the viscoelastic constitutive behavior of uncured resin. The simulation captures intra-layer wrinkles and in-plane waviness defects in the consolidated prepreg, thereby uncovering the mechanism behind fiber wrinkle formation during composite material prepreg consolidation. The accuracy of the model is validated through compression experiments on flat plates and L-shaped structures. The results demonstrate that the proposed embedded digital element model accurately predicts wrinkle defects. Factors such as interlayer friction of the prepreg, consolidation temperature, and mold curvature radius significantly influence the shape and size of wrinkles.

Observations of wrinkling in Non-Crimp Fabrics during multi-ply stack forming using in situ XCT scanning

This paper shows the internal evolution of wrinkles occurring in a single diaphragm forming process using time-resolved in situ XCT scanning. Forming trials were carried out over a curved C-spar geometry using Non-Crimp Fabric (NCF) plies of 45°/135°, 0°/90° and 0°/45° orientations arranged in single-orientation and mixed-orientation stacks. Results show most of the diaphragm movement and change in wrinkle size, shape, and location occurs in the early application (<0.1 bar) of vacuum. The further application of vacuum shows consolidation, with wrinkle size decreasing but shape and location remaining largely unchanged. Single-orientation stacks of 45°/135° plies showed the closest resemblance between initial and final wrinkling, while mixed-orientation stacks showed complex wrinkling due to the 0° plies creating internal ply separation due to excess length. Overall, the study shines a light on the internal interaction between layers that occurs during wrinkling, showing mechanisms only observable with XCT.

Evaluation of the Efficacy of Polydioxanone Threads versus Autologous Plasma Gel for Infraorbital Rejuvenation

Abstract Introduction Infraorbital dark circles refers to presence of darkness of the infraorbital region. Infraorbital dark circles possess no medical harm but signifies cosmetic and psychological burden. Various therapeutic modalities are prescribed for management of infraorbital dark circles without conclusive results. Aim of the Work compare between the efficacy and safety of PDO monothreads versus autologous plasma gel injections for infraorbital rejuvenation. Patients and Methods 40 patients with infraorbital dark circles were included. Patients under went plasma gel injections on the left eye, PDO threads treatment on right eye. All patients were assessed using 3D Antera camera before and after 1 month and 6 months of treatment. Results Both treatment modalities revealed marked cosmetic improvement. Both treatments showed marked response yet results on left eye were superior as regards wrinkle's size, indentation index, texture roughness and average melanin concentration. PDO thread insertion possessed marked significant improvement to wrinkle's size followed by indentation index then texture roughness and average melanin concentration. Plasma gel injection possessed marked significant improvement to wrinkle's depth followed by wrinkle's size then indentation index and finally texture roughness and average melanin concentration. Conclusion Both PDO thread insertion and plasma gel injection exerts beneficial effects in improving periorbital wrinkles and hyperpigmentation. However, plasma gel revealed more potent effects compared to PDO threads.

Smoothing the wrinkle formation and improving dye rejection performance in porous graphene oxide membranes using high surface curvature hollow fiber substrates

Assembly of atomic-scale thin two-dimensional (2D) graphene oxide (GO) nanosheets into a membrane with macroscopic three-dimensional (3D) laminar structure is accompanied by the formation of wrinkles. The size and pattern of wrinkles, which depend on the substrate curvature and the thickness of the 3D laminar structure, adversely affect the separation performance of the membrane. Therefore, smoothing the formed wrinkles is essential to boost the separation performance of GO-based membranes. For the first time, we proposed a new approach to prepare porous hollow fiber (HF) yttria-stabilized zirconia (YSZ) substrates with small-diameter (660–790 μm, outer diameter (OD)) by stretching the nascent HF using gravitational force. Also, using a delayed phase inversion, a plurality of radial micro-channels opening from the interior surface of HFs can be realized. The resultant HF substrates show promising permeation characteristics and good fracture strength owing to their open microstructure and the robustness of YSZ. Small-diameter HF substrates (OD = 660 μm) with higher surface curvature ensured the fabrication of porous GO (PGO) membranes with better dye separation performance. The rejection of methyl red (MR, MW = 269.3 g mol−1) dye molecule for small-diameter HF PGO membranes (OD 660 μm) was 10%–167% higher than that of membranes fabricated using large-diameters (OD 1250–2600 μm). This study shed light on the fabrication of high-performance thin film membranes by tailoring the geometric features of substrates.

Influence of NCF architecture on the morphology of forming induced wrinkling

Biaxial Non-Crimp Fabrics (NCFs) offer the high deposition rates needed to meet the increased production rate targets of the aerospace industry, but formability remains an issue for complex parts. In this study a large scale, complex geometry with a span of 2 m is used to study wrinkle patterns in NCF preforms and how they are influenced by several key NCF parameters. Wrinkle dimensions are captured in 3D scans and used as a proxy metric for “formability”. Results show that whereas location and shape of the wrinkling are driven by geometry, wrinkle size and its metrics (amplitude, wavelength, aspect ratio) are driven by the NCF architecture. In addition, conflicting trends on wrinkle size observed show the complexity of forming as a process. The results presented show the importance of using several characterisation methods and not reducing wrinkling characterisation to a single data point or set.

Comparison of the effects of 2 frequencies of application of photobiomodulation on facial rejuvenation: Controlled, randomized, and double-blind clinical trial.

Skin aging is an irreversible, slow and progressive process, mainly influenced by age, but also by external factors such as ultraviolet radiation, smoking, and alcohol, among others. It is increasingly common to look for procedures that slow down skin aging by limiting or hiding its effects on appearance. Studies have shown the benefits of photobiomodulation (PBM) for the skin, especially with the use of red light-emitting diodes. However, there is a high level of variability in the treatment parameters and frequency of application. The objective of this study is to compare the effects of PBM with a light-emitting diode mask (660 nm, 6.4 mW/ cm², 8,02 J/ cm², 5.02 mW, 21 minutes) on facial rejuvenation using 2 frequency applications for 4 weeks: one group will receive PBM application on the face, twice a week and another group will receive PBM application 3 times a week. A group with simulated PBM applied twice a week for 4 weeks will be used as a control. The treatment will be performed on female participants aged between 45 and 60 years. After 4 weeks, evaluations of photographic images by specialists (Wrinkle Assessment Scale) as well as the quantitative analysis of the wrinkle size by the Image J software, the depth and width of wrinkles (assessment of face impressions by optical coherence tomography) and the level of Satisfaction with Facial Appearance Overall will be compared with data collected before the start of the study. All data will be analyzed statistically according to their distribution, seeking a level of statistical significance of 0.05. This protocol was approved by the Research Ethics Committee of the Nove de Julho University (acceptance number: 4.365.565). This trial has been registered in ClinicalTrials.gov (ID: NCT04911140). This study is recruiting.

Random wrinkle structures for spectrum preserved warm white organic light emitting diodes

Surface wrinkles of mesoscopic size were formed by a single photocuring process of an in-house synthesized linear liquid pre-polymer. The linear relationship between the amplitude and the period of the wrinkles indicates the presence of constant compressive strain during the wrinkling process. The stiffness ratio of the hard film to the soft foundation decreases as the initial film becomes thinner, providing a quantitative measure for estimating the wrinkle size. As an application, mesoscopic wrinkles were investigated as optical structures for enhanced light outcoupling and angular spectral stability of red, green, blue, and white organic light emitting diodes.

Maple Leaf Inspired Conductive Fiber with Hierarchical Wrinkles for Highly Stretchable and Integratable Electronics.

Stretchable and durable conductors are significant to the development of wearable devices, robots, human-machine interfaces, and other artificial intelligence products. However, the desirable strain-insensitive conductivity and low hysteresis are restricted by the failure of stretchable structures and mismatch of mechanical properties (rigid conductive layer and elastic core substrate) under large deformation. Here, based on the principles of fractal geometry, a stretchable conductive fiber with hierarchical wrinkles inspired by the unique shape of the maple leaf was fabricated by combining surface modification, interfacial polymerization, and improved prestrain finishing methods to break through this dilemma. The shape and size of wrinkles predicted by buckling analysis via the finite element method fit well with that of actual wrinkles (30-80 μm of macro wrinkles and 4-6 μm of micro wrinkles) on the fabricated fiber. Such hierarchically wrinkled conductive fiber (HWCF) exhibited not only excellent strain-insensitive conductivity denoted by the relative resistance change ΔR/R0 = 0.66 with R0 the original resistance and ΔR the change of resistance after the concrete strain reaching up to 600%, but also low hysteresis (0.04) calculated by the difference in area between stretching and releasing curve of the ΔR/R0 strain under 300% strain and long-term durability (>1000 stretching-releasing cycles). Furthermore, the elastic conductive fiber with such a bionic structure design can be applied as highly stretchable electrical circuits for illumination and monitors for the human motion under large strains through tiny and rapid resistance changes as well. Such a smart biomimetic material holds great prospects in the field of stretchable electronics.

Formability Experiments for Unidirectional Thermoplastic Composites

Reliable composite forming experiments are required to characterize composite formability, to aid material development, and to validate process simulations models. Due to practical reasons, however, typically a limited amount of forming configurations is studied. The objective of this study is, therefore, to develop a methodology for obtaining controlled forming results in a wide range of configurations. Press forming experiments using a dome geometry were used to explore the formability of two commercial unidirectional thermoplastic composite materials. A variety of forming configurations was employed by changing the blank dimensions and layup. The observation of wrinkling defects was simplified by leaving an additional 3 mm tool gap. Blank width and layup had the most influence on the wrinkling severity, followed by blank thickness and length. Quasi-isotropic layups were found to produce wrinkles in nearly all cases, confirming a difficulty in general to form double curved parts. The size and number of wrinkles in these layups were found to change with the stacking sequence. Cross-ply layups showed better formability, but significant wrinkles were still observed depending on the orientation of the blank relative to the layup. The formability experiments using a dome geometry provided a reliable methodology for controlled forming results in many configurations using a generic toolset. Additionally, a comprehensive comparison of formability for two commercial thermoplastic UD materials in a variety of scenarios was provided.

Drying-Induced Surface Wrinkles Generated on Chitosan Films Having Polyion Complex Skin Layers: Effects of Physical Properties of Skin Layers and Substrates on Surface Wrinkling upon Drying

Abstract The effects of the physical properties of skin layers and substrates on drying-induced surface wrinkling are investigated with a system using chitosan films having polyion complex (PIC) skin layers. The PIC layers are fabricated with diverse anionic polymers having similar molecular weights on a chitosan (CS) film surface, and the films are dried. In all cases, surface wrinkles form but their sizes vary widely depending on the molecular structure. In particular, wrinkles formed with ligninsulfonate are much larger than those formed with the others. The skin layers differ significantly in surface hardness but not in thickness, indicating that wrinkle sizes induced by PIC skin layers are predominately determined by the hardness of the layers or by physical properties affected by hardness, such as shrinkage volume. The effects of the elastic moduli and shrinkage volume of the substrates are evaluated with higher molecular weight CS and surface-deacetylated chitin nanofiber composite CS films that have different elastic moduli but show very similar swelling–drying behaviors. The wrinkle sizes and skin layer thicknesses also suggest that wrinkle size in this system depends on the hardness of the skin layers or on the physical properties affecting the hardness.

Preforming of non-crimp fabrics with distributed magnetic clamping and Bayesian optimisation

A novel preforming process was developed for non-crimp fabric (NCF) materials that generated in-plane tension through discontinuous blank boundary conditions. The method employed magnetic clamps and was designed to be both flexible and scalable, with clear routes to industrialisation. The capability of the process was explored in physical trials for a hemispherical and a cubic geometry. Characterisation of a biaxial veiled NCF showed the veil had a dominant effect on the bending mechanics. Subsequently a macroscale finite element model was developed to include an efficient bending idealisation and non-orthogonal in-plane material behaviour. Finally, global process optimisation of the preforming process was demonstrated. The optimisation approach used Gaussian process modelling with a periodic kernel to estimate the wrinkle size for untested clamping arrangements and then deployed Bayesian optimisation to find the optimal configuration. Results indicated that distributed magnetic clamping was effective and amenable to surrogate modelling.

Reconfigurable Micro- and Nano-Structured Camouflage Surfaces Inspired by Cephalopods.

Wrinkled surfaces and materials are found throughout the natural world in various plants and animals and are known to improve the performance of emerging optical and electrical technologies. Despite much progress, the reversible post-fabrication tuning of wrinkle sizes and geometries across multiple length scales has remained relatively challenging for some materials, and the development of comprehensive structure-function relationships for optically active wrinkled surfaces has often proven difficult. Herein, by drawing inspiration from natural cephalopod skin and leveraging methodologies established for artificial adaptive infrared platforms, we engineer systems with hierarchically reconfigurable wrinkled surface morphologies and dynamically tunable visible-to-infrared spectroscopic properties. Specifically, we demonstrate architectures for which mechanical actuation changes the surface morphological characteristics; modulates the reflectance, transmittance, and absorptance across a broad spectral window; controls the specular-to-diffuse reflectance ratios; and alters the visible and thermal appearances. Moreover, we demonstrate the incorporation of these architectures into analogous electrically actuated appearance-changing devices that feature competitive figures of merit, such as reasonable maximum areal strains, rapid response times, and good stabilities upon repeated actuation. Overall, our findings constitute another step forward in the continued development of cephalopod-inspired light- and heat-manipulating systems and may facilitate advanced applications in the areas of sensing, electronics, optics, soft robotics, and thermal management.

Structural response of steel lined pipes under cyclic bending

Motivated by reeling installation of mechanically-lined offshore steel pipes, the present paper investigates the structural performance of a bi-material lined pipe under cyclic bending, using advanced finite element tools. A three-dimensional finite element model is developed, simulating the manufacturing process of the lined pipe in the first stage of the analysis, followed by the cyclic bending response of the lined pipe in the second stage. Five bending cycles are considered, representing the two installation cycles and three additional cycles of a failure-repair scenario. The loading cycles impose a bending curvature range corresponding to the strains developed during a typical reeling installation process. Different loading patterns are considered and their effect on liner performance are investigated. The results show that the application of reverse (negative) curvature during the loading cycles, representing the straightener, has a significant influence on the wrinkle size of the liner developed at the two critical generators, and its rate of increase, compared with cyclic bending patterns with non-negative curvature. Numerical results on imperfection sensitivity are obtained, considering two types of imperfection of the liner pipe. In addition, the structural performance of liners with different thickness is examined, and the results show that there exists a minimum value of wall thickness, above which the liner does not exhibit local buckling at the end of the cyclic loading history. The beneficial effect of internal pressure on liner cyclic response is also verified, especially for thin-walled liners, preventing the development of wrinkles. Finally, the effect of manufacturing process is examined, showing the superior structural performance of partially-heated lined pipes, with respect to fully-heated lined pipes, and to lined pipes manufactured by purely-mechanical process.

Mannose-6-phosphate complex and improvement in biomechanical properties of the skin.

BackgroundThe dermis is composed of a tangle of macromolecules that provides the skin its biomechanical properties. During chronological aging, fibroblasts lose their ability to synthesize collagen and an accumulation of matrix metalloproteinases leads to an increase in collagen degradation. As a result, there is a decline in the biomechanical properties of the skin. Skin aging is accelerated by external factors such as UV radiation and pollution, which induce accumulation of oxidants, and so of oxidized proteins in the skin.AimsAtomic force microscopy (AFM) has emerged as an alternative method for studying the biomechanical properties of skin cells and tissues.Methods/ResultsThus, we identified mannose‐6‐phosphate complex as a new powerful molecule capable of reversing the visible signs of aging by reorganizing the collagen network of the dermis and by improving the skin biomechanical properties. This effect was correlated with clinical studies that showed a marked antiaging effect through a reduction in the number of crow's feet and in the depth and size of neck wrinkles.ConclusionMannose‐6‐phosphate complex appeared to be able to protect proteins in the dermis scaffold against oxidation and degradation, allowing an improvement in the skin biomechanical properties.

Chemical Leaching of Al3Ni and Al3Ti Alloys at Room Temperature

Al3Ni and Al3Ti alloys were prepared by arc melting and exposed to chemical leaching in 5M NaOH at room temperature. In case of Al3Ni alloy, Al reached phases react with the leaching solution to produce nanoporous nickel with a pore diameter in the range of ~10–20 nm. Only pure Al phase of Al3Ti alloy chemically reacts with the production of a dense wrinkled surface with a wrinkle size of ~50–100 nm.

Modulating cellular hepatic fibrosis with anisotropic wrinkled topography

The foreign body response caused by implanted biomaterials hampers their close integration and thereby result in a failure of the implant or tissue-engineering scaffolds, which represent a huge challenge. Here, we prepare anisotropic micro−/nano-wrinkled surfaces on polydimethylsiloxane that mediates hepatic stellate cell (HSC) responses and hepatic fibrosis. It is found that LX-2 cell attachment and morphology are greatly dependent on the wrinkle sizes. Further, the gene and protein expressions of hepatic fibrosis markers (i.e., α-SMA and Col-I) on wrinkled PDMS surface were reduced compared to the control group. Moreover, anisotropic wrinkled surfaces could accelerate the degradation of collagen by increasing the expression of matrix metalloproteinases (MMPs) and decreasing the formation of MMPs inhibitors. This study provides an effective strategy for reducing the fibrotic response and thus improving the efficacy and safety of novel tissue-engineering scaffolds and implants.

A study on clinical effectiveness of cosmetics containing human stem cell conditioned media

BackgroundWith the steadily increasing trend of functional cosmetics consumption, the public is increasingly expecting the efficacy of cosmetics, and in order to meet these consumer needs, the development of various effective raw materials, as well as products through technical convergence research, has been activating focusing on dermatology. In the Republic of Korea, much attention was paid to cosmetic raw materials using human stem cells as a new growth engine at the end of the 2000s. Accordingly, the Ministry of Food and Drug Safety implemented the Regulations on Cosmetic Safety Standards, etc., which contains the safety standards of human-derived cell and tissue culture as raw materials for cosmetics.MethodsTwice a day, morning and evening, for 28 days, 3 mL of the sample provided for each subject was applied onto the entire face using an airbrush. The subjects were divided into a control group (C), an experimental group 1 (ADSC-CM 5% group, E1) and an experimental group 2 (polymersome-containing of ADSC-CM 5% group, E2), and there were 20 subjects in each group.ResultsMoisture content on the U-zone, melanin and erythema of lid-cheek, overall size and depth of eye wrinkles, and skin roughness of the items showed significant differences among all three groups. More specifically, E1 had a higher rate of skin improvement than C, and E2 had the highest skin improvement rate in all items: skin moisture content, transepidermal water loss (TEWL), melanin and erythema of lid-cheek, eye wrinkles, and skin roughness of lid-cheek.ConclusionsThe effectiveness of ADSC-CM was verified in all items: increases in moisture content, decrease in TEWL, and improvements of whitening and wrinkles. Moreover, the effectiveness of ADSC-CM was observed as higher in samples of polymersome-containing ADSC-CM than those of raw material ADSC-CM. Furthermore, percutaneous absorption was improved compared with previous studies on formulations in relation to polymersome at the same concentration of ADSC-CM, thereby resulting in higher effectiveness.Trial registrationKorea National Institute for Bioethics Policy, P01–201809–13-001, Registered 06 September 2018, http://public.irb.or.kr/.

From surface microrelief to big wrinkles in skin: A mechanical in-silico model

A major concern associated with skin, the largest organ of our body, is how to prevent it from wrinkling and aging. Understanding the mechanics of skin wrinkling can provide useful insight into skin aging prevention. However, despite decades of endeavors the underlying mechanism of skin wrinkling and aging remains poorly understood. This paper explores the effect of geometrical and mechanical properties of skin on its wrinkling via an integrated theoretical and computational analysis. The skin is modeled with a soft structure having different layers with various thicknesses and material properties. Innovatively, the pattern of skin microrelief is generated and mapped on the model to investigate its effect on the formation of primary lines, secondary lines, and big wrinkles of skin. Analytical interpretation provides preliminary insight into the critical compressive strain for the model skin to start wrinkling, while advanced computational models with surface microrelief offer clues for the skin’s post-wrinkling complex morphology. In particular, tissue geometry, material properties, and microrelief pattern are explored as the determinant parameters to control the location, size, and patterns of skin wrinkles. Our findings allude that the characteristics of compression-induced wrinkles are primarily determined by the geometrical and material property of skin layers rather than the genuine skin microrelief. However, microrelief plays a pivotal role in regulating and determining the locations of primary and secondary wrinkle lines. The edges of the microrelief units are favorable paths for evolving primary and secondary lines. Post-wrinkling analysis reveals that in addition to the periodic sinusoidal pattern, several secondary complex patterns such as non-symmetric periodic, period-doubling and self-contacting folds are observed in the compressed model of skin. Results of the study also show that wrinkle patterns highly depend on the thickness and material property of Stratum Corneum (SC), the outermost layer of skin.