Properties Of Skins Research Articles

Numerical investigation into turbulent drag reduction via the application of pufferfish spine-inspired cone microstructures in Suboff models

The effective reduction of seawater drag is pivotal in enhancing the speed and minimizing the energy consumption of submarines, which has significant implications in the fields of energy and defense. Surface bionics has emerged as one of the leading techniques for drag reduction. Current research primarily focuses on replicating the groove-like structures observed on shark skins and the flexible properties of dolphin skins. However, the application of cone microstructures on submarine surfaces remains relatively underexplored. In this study, a novel arrangement of bionic drag-reducing microstructures is employed to modify the turbulence structure surrounding the submarine by incorporating bionic cone microstructures at both the front and rear ends of the submarine. Numerical simulations were performed using the SST k-ω turbulence model to evaluate the impact of these frontal microstructures on drag reduction under varying Reynolds numbers, spacings, and positions, as well as the tail microstructures’ effect at different Reynolds numbers, heights, and circumferential separation angles. The findings reveal that positioning microstructures at the submarine’s head increases the drag reduction rate proportionally with the distance from the apex, displaying an inverse relationship between spacing and drag reduction rate. Conversely, an increase in cone separation angle at the tail leads to a decrease in the overall drag reduction rate. At the same time, an inverse proportionality is observed between cone height and drag reduction rate. This suggests that cone microstructures play a dual role: mitigating friction drag greatly and augmenting pressure drag, thereby achieving overall drag reduction. Moreover, these cone microstructures disrupt eddy currents within the boundary layer surrounding the submarine, restraining the propagation of turbulent momentum transfer in both the head and tail regions. This research not only pioneers a novel drag reduction strategy for underwater vehicles but also sparks new avenues for their optimized surface design.

Soft Magnetic Skin's Deformation Analysis for Tactile Perception

Soft magnetic skins have been widely adopted for tactile perception due to their high accuracy and simple wiring advantages. However, the perceptual properties of magnetic skins are limited by information mapping relationships with weak interpretation. To overcome existing limitations, dynamic Young's modulus (DYM) is proposed in this paper based on strain energy density function to precisely describe the compression stiffness of magnetic skins. Furthermore, a highly interpretable and broadly applicable method is derived using DYM to analyze a cylindrical magnetic skin's deformation process as the skin deformed under external mechanic load. Extensive experiments in simulated and real situations with different deformations are carried out to verify the proposed method. Experimental results demonstrate that 0.14% and 0.43% relative errors in simulated and real environments, respectively, can be reached. Moreover, the proposed method can achieve minimum errors in almost all situations than data-driven or state-of-the-art analysis approaches. And the generality of the proposed method is validated by experiments conducted on skins with two different shapes. These promising results indicate the potential of the proposed method in establishing practical information mapping relationships for magnetic skins, probably addressing the significant challenges for magnetic skin application in complex scenarios.

Generalized Analysis and Unified Design of EM Skins

A generalized formulation is derived for the analysis of the field manipulation properties of electromagnetic skins ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">EMS</i> s) in the working regimes of interest for wireless communications. Based on such a theoretical framework, a unified method for the design of anomalous-reflecting and focusing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">EMS</i> s is presented. Representative results, from a wide set of numerical experiments, are reported and validated with full-wave <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">HFSS</i> simulations to give the interested readers some insights on the accuracy, the effectiveness, and the computational efficiency of the proposed analysis/synthesis tools.

Free vibration analysis of the sandwich structured composite annular plates: Numerical and experimental investigation

Sandwich structures are interesting structural elements due to their high stiffness-to-weight ratio, high fatigue resistance, and excellent vibration characteristics. The aerospace industry relies heavily on these types of structures considering the different optimized materials and shapes available for sandwich construction. In the present study, vibration aspects of annular sandwich structures with composite laminates and a 3D printed honeycomb core are investigated in both the numerical and experimental methods. Amongst the various shapes of sandwich structures, annular sector plates are predominantly used in the construction of modern bridges, aircrafts, and automobile parts. Furthermore, the investigation of annular sandwich plates featuring GFRP facesheet and 3D printed PLA cores are studied in a very limited extent. In order to obtain the sector plates experimentally, Glass Fiber Reinforced Polymer (GFRP) laminates are fabricated by hand layup techniques, and the 3D printing Poly-lactic Acid (PLA) honeycomb core is manufactured using Fused Deposition Modelling (FDM). The material properties of honeycomb core and composite skins are estimated with the help of Gibson formulation and rule of mixture, respectively. Based on available literature, the analysis approach is validated through numerical analysis using ANSYS Finite Element (FE) software. Also, the frequency responses of annular sandwich plate were measured in both experimental and numerical analysis and the results showed good agreement. However, in order to describe the effectiveness of annular composite sandwich plates, parametric studies are carried out in terms of natural frequencies and mode shapes with different configurations of core geometry, ply orientation, boundary constraints, and inner to outer radius ratio. The research outcome highlights that the optimum angle ply orientation, core height of 12.5 mm with clamped–clamped condition and inner to outer radius of 0.75 mm yields better structural stiffness.

Bio-inspired ionic skins for smart medicine.

Ionic skins are developed to mimic the mechanical properties and functions of natural skins. They have demonstrated substantial advantages to serve as the crucial interface to bridge the gap between humans and machines. The first-generation ionic skin is a stretchable capacitor comprising hydrogels as the ionic conductors and elastomers as the dielectrics, and realizes pressure and strain sensing through the measurement of the capacitance. Subsequent advances have been made to improve the mechanical properties of ionic skins and import diverse functions. For example, ultrahigh stretchability, strong interfacial adhesion, self-healing, moisturizing ability, and various sensing capabilities have been achieved separately or simultaneously. Most ionic skins are attached to natural skins to monitor bio-electrical signals continuously. Ionic skins have also been found with significant potential to serve as a smart drug-containing reservoir, which can release drugs spatially, temporally, and in a controllable way. Herein, this review focuses on the design and fabrication of ionic skins, and their applications related to smart medicine. Moreover, challenges and opportunities are also discussed. It is hoped that the development of bio-inspired ionic skins will provide a paradigm shift for self-diagnosis and healthcare.

Superior Damage Tolerance of Fish Skins.

Skin is the largest organ of many animals. Its protective function against hostile environments and predatorial attack makes high mechanical strength a vital characteristic. Here, we measured the mechanical properties of bass fish skins and found that fish skins are highly ductile with a rupture strain of up to 30-40% and a rupture strength of 10-15 MPa. The fish skins exhibit a strain-stiffening behavior. Stretching can effectively eliminate the stress concentrations near the pre-existing holes and edge notches, suggesting that the skins are highly damage tolerant. Our measurement determined a flaw-insensitivity length that exceeds those of most engineering materials. The strain-stiffening and damage tolerance of fish skins are explained by an agent-based model of a collagen network in which the load-bearing collagen microfibers assembled from nanofibrils undergo straightening and reorientation upon stretching. Our study inspires the development of artificial skins that are thin, flexible, but highly fracture-resistant and widely applicable in soft robots.

Water-Modulated Biomimetic Hyper-Attribute-Gel Electronic Skin for Robotics and Skin-Attachable Wearables.

Electronic skin (e-skin), mimicking the physical-chemical and sensory properties of human skin, is promising to be applied as robotic skins and skin-attachable wearables with multisensory functionalities. To date, most e-skins are dedicated to sensory function development to mimic human skins in one or several aspects, yet advanced e-skin covering all the hyper-attributes (including both the sensory and physical-chemical properties) of human skins is seldom reported. Herein, a water-modulated biomimetic hyper-attribute-gel (Hygel) e-skin with reversible gel-solid transition is proposed, which exhibits all the desired skin-like physical-chemical properties (stretchability, self-healing, biocompatibility, biodegradability, weak acidity, antibacterial activities, flame retardance, and temperature adaptivity), sensory properties (pressure, temperature, humidity, strain, and contact), function reconfigurability, and evolvability. Then the Hygel e-skin is applied as an on-robot e-skin and skin-attached wearable to demonstrate its highly skin-like attributes in capturing multiple sensory information, reconfiguring desired functions, and excellent skin compatibility for real-time gesture recognition via deep learning. This Hygel e-skin may find more applications in advanced robotics and even skin-replaceable artificial skin.

Antioxidant Activity of Raw and Roasted Peanut (Arachis hypogaea L.) Skins Extracts

Background: Peanut skins are a by-product from peanut but with low socio-economic value despite having appreciable amounts of bioactive phytochemicals. Studies are on-going to remove some astringent properties in peanut skins and improve its values. In this study, the in vitro antioxidant activity of raw peanut skins and roasted peanut skins extracts were determined in hydro alcoholic medium. Materials and Methods: The raw and roasted peanut skins powders were each subjected to extraction procedure in 70% methanol for 48 hr. The phytochemical screening including total phenolic and flavonoid contents (TPC, TFC) were determined. The antioxidant activity including DPPH radical scavenging, Fe2+-chelating, ferric reducing antioxidant property (FRAP), OH- radical scavenging and reducing power assays were determined and compared against standard antioxidants. Results: The results showed significantly higher (p&lt;0.05) TPC and total antioxidant capacity in the raw extract compared to the roasted extract. The roasted peanut skins extract showed significantly higher (p&lt;0.05) DPPH radical, OH- radical scavenging capacity, Fe2+-chelating and ferric reducing antioxidant property compared to the raw peanut skins extract. Both extracts each produced concentration dependent percentage inhibitions which were significantly lower than the antioxidant standards used. Conclusion: The results showed that roasting improved the in vitro antioxidant properties of the peanut skins compared to the raw peanut skins. This could add value to its use as functional food component, antioxidant and in animal feed industries.

Stability analysis of a spinning soft-core sandwich beam with CNTs reinforced metal matrix nanocomposite skins subjected to residual stress

The stability of a soft-cored spinning viscoelastic sandwich beam and carbon nanotubes (CNTs) reinforced metal matrix nanocomposites (MMNCs) skin subjected to residual stress have been investigated. The metal matrix nanocomposites (MMNCs) skins are symmetrical and isotropic. In addition, these skins reinforced with uniform and functionally graded (FG) distributions of carbon nanotubes (CNTs) are considered. The soft-core of the sandwich beam is deemed to be elastomeric and has internal damping of viscoelastic type. The skin layers of the sandwich beam are subject to residual stresses caused by the production process. Also, the effective material properties of skins are obtained using the rule of mixture (ROM) and Halpin-Tsai (H-T) micromechanics models. First, the governing equations of motion of a spinning viscoelastic sandwich beam are obtained using the Hamilton principle. Then, the sandwich beam's natural frequencies are calculated using the differential quadrature method (DQM). The effects of CNTs distribution, nanotube volume fraction, spinning speed, critical loading, the thickness of the core, axial force, and residual stress on the sandwich beam's natural frequency and stability regions are investigated. According to the results of this study, based on the sandwich beam's different spinning speeds, it is possible to estimate the optimal amount of core thickness to prevent instability, which can be very important in the design of spinning sandwich structures.

Fatigue-free artificial ionic skin toughened by self-healable elastic nanomesh

Robust ionic sensing materials that are both fatigue-resistant and self-healable like human skin are essential for soft electronics and robotics with extended service life. However, most existing self-healable artificial ionic skins produced on the basis of network reconfiguration suffer from a low fatigue threshold due to the easy fracture of low-energy amorphous polymer chains with susceptible crack propagation. Here we engineer a fatigue-free yet fully healable hybrid ionic skin toughened by a high-energy, self-healable elastic nanomesh, resembling the repairable nanofibrous interwoven structure of human skin. Such a design affords a superhigh fatigue threshold of 2950 J m−2 while maintaining skin-like compliance, stretchability, and strain-adaptive stiffening response. Moreover, nanofiber tension-induced moisture breathing of ionic matrix leads to a record-high strain-sensing gauge factor of 66.8, far exceeding previous intrinsically stretchable ionic conductors. This concept creates opportunities for designing durable ion-conducting materials that replicate the unparalleled combinatory properties of natural skins more precisely.

An electric‐driven variable stiffness morphing skin: Preparation and properties

AbstractWith variable stiffness properties, shape memory polymers (SMPs) become the most promising materials of morphing skins. In this article, based on hydro‐epoxy resin/carboxyl‐terminated butadiene acrylonitrile/maleic anhydride matrix, composite morphing skins are prepared by doping conductive carbon black (CB). By adjusting the content of CB, in‐plane and out‐of‐plane properties of skins can be adjusted. Because of the in‐plane tensile stress acting on the skin during flight, tensile test is required. The results indicate that in‐plane tensile strength of skin decreases as the CB content increases. In electrical resistivity test, the electronic resistivity of skin decreases sharply at a low‐percolation threshold (1.9 wt%) and then maintains a low and steady level. As for out‐of‐plane properties, thermo‐ and electro‐active shape memory test are studied. All of the selected typical composite skins have 100% thermo‐driven shape recovery rate. Some skins have 100% thermo‐driven shape fixity rate and fast electro‐active shape recovery speed. When the CB content is 2.6 or 3 wt%, the skin can recover its out‐of‐plane deformed shape completely at 150 V. Benefit from easy control and remote drive, the composite SMP skins are proved to be a promising candidate material for morphing skins.

Antioxidant Activity and Phenolic Compounds Profile of Pistachio Skins (Pistacia vera L., cultivars Kallehghuchi and Ohadi)

Background: Pistachio with scientific name Pistacia vera L., a native plant in Asia, is a member of Anacardiaceae family. Pistachio nuts and skins are known as a rich source of phenolic compounds with antioxidant, anti-inflammatory and antimicrobial properties. Objectives: In current study industrial production of phenolic compounds with antioxidant activity was investigated because of high mass production of Pistachio skin in Iran. Method: The extraction of two pistachio cultivars, namely Kallehghuchi and Ohadi were carried out by using two methods (maceration and ultrasonic extraction) and four solvents (acetone 70%, ethanol 50%, methanol 50% and water). Antioxidant properties of pistachio skins were determined by three methods (Folin-Ciocalteu colorimetric method, DPPH assay, TLC/DPPH analysis). Results: The results showed that the highest content of total phenolic compounds were measured by ultrasonic and maceration methods related to Ohadi and Kallehghuchi in acetone solvents 17.4±0.04 and 17.26±0.1 mg/g DW respectively. The highest antioxidant activity in were measured by ultrasonic and maceration methods related to Ohadi in acetone and water solvents IC50=0.057±0.001 and 0.059±0.002 µg/mL respectively. By TLC/DPPH analysis, gallic acid, 4-hydroxy-3, 5-dimethoxy benzoic acid, tannic acid and some unidentified compounds were determined. By HPLC analysis, gallic acid, coumaric acid, cinnamic acid, 4-hydroxy-cinnamic acid and 4-hydroxy benzoic acid were determined. Conclusion: In conclusion, this study clarifies some special biochemical characteristics of pistachio skins. Therefore, according to results of the study pistachio skins could be successfully used in food and pharmaceutical industries.

Kinetics of Oil Absorption and Moisture Loss during Deep-Frying of Pork Skin with Different Thickness.

We have investigated different properties (thickness, moisture loss, oil uptake, breaking force, color, puffing ratio during 0.5–5 min frying, microstructure, and sensory evaluation) of raw pork skins with varying thickness (2, 3, and 4 mm) after drying, intended as deep-fried snacks. We have found that the oil content, breaking force, and puffing ratio of fried pork skin with different raw skin thickness have no significant difference under similar water content (1.68–1.98 g/100 g wet weight basis, wb) after 3–5 min of deep-frying at 180 °C. Additionally, sensory score results have shown that fried pork skins with 4 mm raw skin thickness had lower flavor, texture, and overall acceptability than those with 2 mm and 3 mm raw skin thickness. Scanning electron micrographs (SEM) have revealed less holes and irregular and crack microstructure in fried pork skins with 4 mm raw skin thickness than in other groups. Different thickness of raw pork skins resulted in different effects in microstructure and influenced water evaporation and oil uptake of fried pork skin. Finally, we have proposed the kinetic equations of water loss and oil uptake of fried pork skins. Fried pork skin from raw skin thicker than 4 mm need frying at temperature higher than 180 °C to improve their puffing ratio and sensory acceptability.

A review of mechanochromic polymers and composites: From material design strategy to advanced electronics application

The design and fabrication of functional polymers with fascinating mechanochromic properties are of profound significance to their prospective applications, such as wearable electronic skin, smart screen, artificial muscle, encryption, and anti-counterfeiting devices. Drawn inspiration from color-changing properties of biological skins, numerous approaches, from molecular synthesis to special biomimicry engineering, have been employed to construct flexible stimuli-responsive materials with superior mechano-stimulated optical change performance. In this review, we highlight and discuss recent important progress in material structure design strategy for mechanochromic polymers and composites. These optical variations primarily originate from the force-induced molecular structure change, disruption of intermolecular interaction, evolution of physical photonic and morphological structure. Moreover, according to their respective structure-property relationships, their multifunctional applications in advanced electronics field are also demonstrated with representative examples. Furthermore, a summary and perspective regarding the existing challenges in this field will be discussed, aiming to provide valuable insight into their future developments. We believe this feature review will bring helpful guidance to readers for choosing effective chromogenic material design method to satisfy different application requirements.

Chitosan/Polyvinyl Alcohol/ Lauramidopropyl Betaine/2D-HOF Mixed Film with Abundant Hydrogen Bonds Acts as High Mechanical Strength Artificial Skin.

The mechanical properties of artificial skins are complicated to maintain under ensuring air permeability and antimicrobial. Thus, a series of hydrophilic antimicrobial polymer networks are prepared by crosslinking chitosan and polyvinyl alcohol with the lauramidopropyl betaine and hydrogen bond organic framework (CS/PVA/LPB/2D-HOF). The mechanical performance of the control groups and the complex are systematically evaluated to attain an artificial strength skin. The CS/PVA/LPB/2D-HOF complex exhibits strong mechanical abilities than other control groups. By analyzing the IR spectra and the morphology, the synergistic effect of hydrogen bonds between molecules and cracks significantly improves the mechanical properties of the complex. Its maximum tensile strength can reach 29 MPa, and its maximum load capacity can reach 3700 g. Notably, the composite membrane also performs an excellent antimicrobial activity. In vivo and in vitro experiments show that the hybrid membrane can promote tissue regeneration and wound healing (95％). These results may open up the opportunity for future composite material investigations in the artificial skin and tissue engineering field.

Physicochemical, microstructural, and antioxidant properties of skins from pomaces of five virginia-grown grape varieties and their response to high hydrostatic pressure processing

Physicochemical, microstructural, and antioxidant properties of skins from pomaces of five virginia-grown grape varieties and their response to high hydrostatic pressure processing

Assessment of the Impact of Decellularization Methods on Mechanical Properties of Biocomposites Used as Skin Substitute.

This work aimed to assess the impact of acellularization and sterilization methods on the mechanical properties of biocomposites used as a skin substitute. On the basis of the statistical analysis, it was ascertained that the values of the Young modulus for the samples before the sterilization process—only in the cases of substances such as: trypsin, 15% glycerol and dispase—changed in a statistically significant way. In the case of dispase, the Young modulus value before the sterilization process amounted to 66.6 MPa, for trypsin this value equalled 33.9 MPa, whereas for 15% glycerol it was 11 MPa. In the case of samples after the completion of the sterilization process, the analysis did not show any statistically significant differences between the obtained results of Young’s modulus depending on the respective reagents applied. It was confirmed that different methods of acellularization and the process of sterilization effect the alteration of mechanical properties of allogeneic skins. In the case of the decellularization method using SDS (Sodium Dodecyl Sulfate), liquid nitrogen and 85% glycerol the highest values of strain were observed. In the authors’ opinion, it is the above-mentioned methods that should be recommended in the process of preparation of skin substitutes.

Barrier properties of fungal fruit body skins, pileipelles, contribute to protection against water loss

The permeability of intact fungal fruit body skins (pileipelles) with respect to water and oxygen was determined for the first time. Methods that have been successfully applied to plant surfaces were used to study isolated pileipelles. Mechanically isolated skins from five genera of Basidiomycota (species of Amanita, Russula, Stropharia, Tapinella, and Tricholomopsis) were mounted between two compartments simulating the inner (fruit body) and the outer (aerial) space. Fluxes of water and oxygen across the skins were measured. Water loss via intact skins differed markedly from evaporation of water from a water surface. The skins reduced water loss by factors of 10 to 30, with permeability ranging from 2.8 to 9.8 × 10−4 ms−1. Oxygen permeability was much lower and ranged from 0.8 to 6.0 × 10−6 ms−1. Chloroform-extractable substances play a minor, but significant role as transport barrier during water permeance. Water and oxygen permeability were dependent on the humidity in the aerial compartment. Higher humidity in the air increased permeability and the hydration/water content of the skins. The ecological implications include impacts to fungal growth, sporulation and spore release.

Analytical solution for static and dynamic analysis of FGP cylinders integrated with FG-GPLs patches exposed to longitudinal magnetic field

Motivated by progressive sandwich structures’ usage due to their high strength to weight ratio in different industries, the current paper aimed at evaluating static and dynamic behaviors of three-layered cylinders including FG porous core and two graphene nanoplatelet (GPLs)-reinforced composite as face sheets. The whole sandwich cylinder rests on Pasternak substrate and it is also exposed to a longitudinal magnetic field. Epoxy has used as matrix and GPLs as the reinforcing phases for top and bottom face sheets and based on the rule of mixture and Halpin–Tsai micromechanical models, effective values for mechanical properties of skins are gained. Besides, regarding the integrity of current research, all layers of model are assumed to be FG, which means for the porous core the placement of the pores is considered and for the faces, the GPLs dispersion patterns are regarded. Among different shell theories, sinusoidal shear deformation shells theory (SSDST) is utilized to define displacement components along with the major axes. Hamilton’s principle is hired to attain governing equations for vibrational and buckling analyses. In the end, the effects of different variables’ alternation as the model’s geometry, foundation moduli, mode number, and mid-radius on vibrational and buckling behaviors are interpreted in type of different plots and tables. Pores’ placement and GPLs dispersion patterns play important roles in static and dynamic responses of the under-consideration cylinder. The outcomes of this study may help to create more efficient engineering structures such as pressure vessels.

The efficiency of using protein hydro-lyzate to stimulate the reproductive function of minks and improve the commercial properties of animal skins

From the point of view of solving the problem of feed supply in fur farming, the use of biologically active additives that normalize the protein balance is of great interest. The hydrolyzate obtained by the technology developed by us from the waste of fur farming is a highly digestible protein, is characterized by a high content of amine nitrogen, and contains all non-replaceable amino acids. The introduction of hydrolyzate from sable muscle tissue into the main diet of minks allowed to reduce by 1.3 times the number of missing female minks, to increase the yield of mink puppies per main female, increase the viability of the offspring. The efficiency of feeding the protein hydrolyzate in the diet of caged minks was assessed by the commercial properties of the skins. The most important indicators are the thickness of the skin and the ratio of its layers, on which the duration of processing of raw materials during production operations and indicators of the physical and mechanical properties of the skins depend. Analysis of the obtained measurements made it possible to conclude that feeding with protein hydrolyzate led to an increase in the thickness of the skin of various topographic areas of mink skins. The maximum value of the epidermis thickness was observed on the rump part, the minimum - on the spinal region, while the maximum number of guard hairs was noted on the spinal part, the minimum - on the lateral part of the mink skins. Thus, the results obtained indicate the effectiveness of using a protein hydrolyzate to stimulate the reproductive function of minks and improve the commercial properties of animal skins.