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Ma J, Zhang X, Yin D, Cai Y, Shen Z, Sheng Z, Bai J, Qu S, Zhu S, Jia Z. Designing Ultratough Single-Network Hydrogels with Centimeter-Scale Fractocohesive Lengths via Inelastic Crack Blunting. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2311795. [PMID: 38452279 DOI: 10.1002/adma.202311795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 03/03/2024] [Indexed: 03/09/2024]
Abstract
Fractocohesive length, defined as the ratio of fracture toughness to work of fracture, measures the sensitivity of materials to fracture in the presence of flaws. The larger the fractocohesive length, the more flaw-tolerant and crack-resistant the hydrogel. For synthetic soft materials, the fractocohesive length is short, often on the scale of 1 mm. Here, highly flaw-insensitive (HFI) single-network hydrogels containing an entangled inhomogeneous polymer network of widely distributed chain lengths are designed. The HFI hydrogels demonstrate a centimeter-scale fractocohesive length of 2.21 cm, which is the highest ever recorded for synthetic hydrogels, and an unprecedented fracture toughness of ≈13 300 J m-2 . The uncommon flaw insensitivity results from the inelastic crack blunting inherent to the highly inhomogeneous network. When the HFI hydrogel is stretched, a large number of short chains break while coiled long chains can disentangle, unwind, and straighten, producing large inelastic deformation that substantially blunts the crack tip in a plastic manner, thereby deconcentrating crack-tip stresses and blocking crack extension. The flaw-insensitive design strategy is applicable to various hydrogels such as polyacrylamide and poly(N,N-dimethylacrylamide) hydrogels and enables the development of HFI soft composites.
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Affiliation(s)
- Jie Ma
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Xizhe Zhang
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Daochen Yin
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Yijie Cai
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Zihang Shen
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Zhi Sheng
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Jiabao Bai
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Shaoxing Qu
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Shuze Zhu
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Zheng Jia
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
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Zeng L, Liu F, Yu Q, Jin C, Yang J, Suo Z, Tang J. Flaw-insensitive fatigue resistance of chemically fixed collagenous soft tissues. SCIENCE ADVANCES 2023; 9:eade7375. [PMID: 36867693 PMCID: PMC9984180 DOI: 10.1126/sciadv.ade7375] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 01/31/2023] [Indexed: 06/18/2023]
Abstract
Bovine pericardium (BP) has been used as leaflets of prosthetic heart valves. The leaflets are sutured on metallic stents and can survive 400 million flaps (~10-year life span), unaffected by the suture holes. This flaw-insensitive fatigue resistance is unmatched by synthetic leaflets. We show that the endurance strength of BP under cyclic stretch is insensitive to cuts as long as 1 centimeter, about two orders of magnitude longer than that of a thermoplastic polyurethane (TPU). The flaw-insensitive fatigue resistance of BP results from the high strength of collagen fibers and soft matrix between them. When BP is stretched, the soft matrix enables a collagen fiber to transmit tension over a long length. The energy in the long length dissipates when the fiber breaks. We demonstrate that a BP leaflet greatly outperforms a TPU leaflet. It is hoped that these findings will aid the development of soft materials for flaw-insensitive fatigue resistance.
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Affiliation(s)
- Liangsong Zeng
- State Key Lab for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics, Department of Engineering Mechanics, Xi’an Jiaotong University, Xi’an, China
| | - Fengkai Liu
- State Key Lab for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics, Department of Engineering Mechanics, Xi’an Jiaotong University, Xi’an, China
| | - Qifeng Yu
- Shanghai NewMed Medical Corporation, Shanghai, China
| | - Chenyu Jin
- State Key Lab for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics, Department of Engineering Mechanics, Xi’an Jiaotong University, Xi’an, China
| | - Jian Yang
- Department of Cardiovascular Surgery, Xijing Hospital, Air Force Medical University, Xi’an 710032, China
| | - Zhigang Suo
- John A. Paulson School of Engineering and Applied Sciences, Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, MA, USA
| | - Jingda Tang
- State Key Lab for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics, Department of Engineering Mechanics, Xi’an Jiaotong University, Xi’an, China
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3
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Maidment SCR, Strachan SJ, Ouarhache D, Scheyer TM, Brown EE, Fernandez V, Johanson Z, Raven TJ, Barrett PM. Bizarre dermal armour suggests the first African ankylosaur. Nat Ecol Evol 2021; 5:1576-1581. [PMID: 34556830 DOI: 10.1038/s41559-021-01553-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 08/09/2021] [Indexed: 11/09/2022]
Abstract
Ankylosauria is a diverse clade of armoured dinosaurs whose members were important constituents of many Cretaceous faunas. Phylogenetic analyses imply that the clade diverged from its sister taxon, Stegosauria, during the late Early Jurassic, but the fossil records of both clades are sparse until the Late Jurassic (~150 million years ago). Moreover, Ankylosauria is almost entirely restricted to former Laurasian continents, with only a single valid Gondwanan taxon. Spicomellus afer gen. et sp. nov. appears to represent the earliest-known ankylosaur and the first to be named from Africa, from the Middle Jurassic (Bathonian-Callovian) of Morocco, filling an important gap in dinosaur evolution. The specimen consists of a rib with spiked dermal armour fused to its dorsal surface, an unprecedented morphology among extinct and extant vertebrates. The specimen reveals an unrealized morphological diversity of armoured dinosaurs during their early evolution, and implies the presence of an important but undiscovered Gondwanan fossil record.
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Affiliation(s)
- Susannah C R Maidment
- Department of Earth Sciences, Natural History Museum, London, UK. .,School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK.
| | - Sarah J Strachan
- Department of Earth Sciences, University College London, London, UK
| | - Driss Ouarhache
- GERA Laboratory, Faculty of Sciences Dhar El Mahraz, SMBA University, Fez, Morocco
| | - Torsten M Scheyer
- Palaeontological Institute and Museum, University of Zurich, Zurich, Switzerland
| | - Emily E Brown
- Department of Earth Sciences, Natural History Museum, London, UK.,School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
| | | | - Zerina Johanson
- Department of Earth Sciences, Natural History Museum, London, UK
| | - Thomas J Raven
- Department of Earth Sciences, Natural History Museum, London, UK.,School of Environment and Technology, University of Brighton, Brighton, UK
| | - Paul M Barrett
- Department of Earth Sciences, Natural History Museum, London, UK.,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
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Gómez JM, Verdú M, González-Megías A. Killing conspecific adults in mammals. Proc Biol Sci 2021; 288:20211080. [PMID: 34284635 PMCID: PMC8292775 DOI: 10.1098/rspb.2021.1080] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 06/22/2021] [Indexed: 01/19/2023] Open
Abstract
Mammals kill both conspecific infants and adults. Whereas infanticide has been profusely studied, the killing of non-infants (adulticide) has seldom attracted the attention of researchers. Mammals kill conspecific adults by at least four, non-exclusive reasons: during intrasexual aggression for mating opportunities, to defend valuable resources, to protect their progeny and to prey upon conspecifics. In this study, we test which reason is most likely to explain male and female adulticide in mammals. For this, we recorded the presence of adulticide, the ecological and behavioural traits, and the phylogenetic relationship for more than 1000 species. Adulticide has been recorded in over 350 species from the most important Mammalian clades. Male adulticide was phylogenetically correlated with the presence of size dimorphism and intrasexually selected weapons. Female adulticide was phylogenetically associated with the occurrence of infanticide. These results indicate that the evolutionary pathways underlying the evolution of adulticide differ between sexes in mammals. Whereas males commit adulticide to increase breeding opportunities and to compete with other males for mating, females commit adulticide mainly to defend offspring from infanticidal conspecifics.
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Affiliation(s)
- José María Gómez
- Dpto de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (EEZA-CSIC), Carretera de Sacramento s/n, La Cañada de San Urbano, 0-4120 Almería, Spain
| | - Miguel Verdú
- Centro de Investigaciones sobre Desertificación (CSIC-UV-GV), Ctra Moncada-Náquera km 4.5, 46113 Moncada (Valencia), Spain
| | - Adela González-Megías
- Dpto de Zoología, Facultad de Ciencias, Universidad de Granada, Avda Fuentenueva s/n, 18071 Granada, Spain
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Boehm TMSA, Klinger CJ, Gohl C, Lücht M, Baumann KN, Mueller RS. Topical treatment of multiple erosive, ulcerative skin lesions in an Indian rhinoceros (Rhinoceros unicornis). Tierarztl Prax Ausg G Grosstiere Nutztiere 2021; 49:210-214. [PMID: 34157750 DOI: 10.1055/a-1475-3459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
A 30-year-old, intact female Indian rhinoceros (Rhinocerus unicornis) was presented with ongoing erosive, ulcerative skin lesions over a 4-year-period. The lesions appeared to be non-pruritic and non-seasonal. A systemic antibiotic therapy had been unsuccessful. The dermatological examination showed 8 diffusely demarcated areas of erosion, focal ulceration, mild crusting, and moderate erythema ranging from 8 to 20 cm in diameter, bilaterally on the lateral edges of the torso armor plates. The patient had no other clinical abnormalities. Coccoid and rod-shaped bacteria were identified on cytology and a bacterial culture revealed Escherichia coli spp., Staphylococcus dysgalacticae, Stenotrophomonas maltophilia, Corynebacterium spp. and Micrococus spp. A topical product line containing essential fatty acids and plant extracts was administered daily, using a spot-on, spray and balm. Within 3 weeks a substantial alleviation of clinical signs was observed. Multiple impression smears of the lesions and a bacterial culture were negative by day 21. The patient achieved complete remission within 4 months of treatment and maintained remission for the 2-year observation period with continued use of the medication. Topically administered therapeutics containing essential fatty acids and plant extracts may offer a viable treatment option for recurrent cases of bacterial infectious skin lesions in Indian rhinocerotidae.
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Affiliation(s)
| | | | | | | | - Katja N Baumann
- Centre for Clinical Veterinary Medicine, Ludwig Maximilian University
| | - Ralf S Mueller
- Centre for Clinical Veterinary Medicine, Ludwig Maximilian University
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6
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Finite element analysis of a ram brain during impact under wet and dry horn conditions. J Mech Behav Biomed Mater 2021; 119:104400. [PMID: 33893020 DOI: 10.1016/j.jmbbm.2021.104400] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 01/04/2021] [Accepted: 02/10/2021] [Indexed: 11/20/2022]
Abstract
In this study, ram impacts at 5.5 m/s are simulated through finite element analysis in order to study the mechanical response of the brain. A calibrated internal state variable inelastic constitutive model was implemented into the finite element code to capture the brain behavior. Also, constitutive models for the horns were calibrated to experimental data from dry and wet horn keratin at low and high strain rates. By investigating responses in the different keratin material states that occur in nature, the bounds of the ram brain response are quantified. An acceleration as high as 607 g's was observed, which is an order of magnitude higher than predicted brain injury threshold values. In the most extreme case, the maximum tensile pressure and maximum shear strains in the ram brain were 245 kPa and 0.28, respectively. Because the rams do not appear to sustain injury, these impacts could give insight to the threshold limits of mechanical loading that can be applied to the brain. Following this motivation, the brain injury metric values found in this research could serve as true injury metrics for human head impacts.
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7
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Affiliation(s)
- Zachary Emberts
- Department of Ecology and Evolutionary Biology University of Arizona Tucson AZ USA
| | - John J. Wiens
- Department of Ecology and Evolutionary Biology University of Arizona Tucson AZ USA
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8
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Uyeno T, Clark A. On the fit of skins with a particular focus on the biomechanics of loose skins of hagfishes. CAN J ZOOL 2020. [DOI: 10.1139/cjz-2019-0296] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
There is a considerable diversity in how skins fit. Here, we review the function of both tight and loose skins and note that the latter are poorly understood. Analysis of loose skin examples suggest five functional categories: (I) freedom of movement, (II) surface area enhancement, (III) increased structural extensibility, (IV) lubrication, and (V) maladaptive examples arising through sexual or artificial selection. We investigate the skins of hagfishes as a model for understanding loose skin function by examining its structure using histology, standardized puncture resistance testing using the ASTM F1306 protocol, and the effect of internal pressure using a simple inflated balloon model. Skins of hagfishes are composed of multiple layers of cross-helically wound connective tissue fibers of a 45° angle to the longitudinal axis, resulting in a skin that functions as fabric cut “on the bias”. Hagfish skins are relatively yielding; however, skin looseness adds a “structural extensibility” that may allow hagfishes to compensate for low puncture resistance. Physical balloon models, with stiff cores that limit length changes, show that only low pressures allow short loop radii without local buckling. Hagfishes represent ideal organisms for studying loose skin function because their skins seem to fit in all functionally adaptive categories.
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Affiliation(s)
- T.A. Uyeno
- Department of Biology, Valdosta State University, 1500 North Patterson Street, Valdosta, GA 31698, USA
| | - A.J. Clark
- Department of Biology, College of Charleston, 66 George Street, Charleston, SC 29424, USA
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9
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Kohari D, Hongo T, Inoue K. The influence of stable fly invasion on the behavior of captive black rhinoceros (Diceros bicornis). J Vet Behav 2020. [DOI: 10.1016/j.jveb.2019.10.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Penny SG, White RL, Scott DM, MacTavish L, Pernetta AP. Using drones and sirens to elicit avoidance behaviour in white rhinoceros as an anti-poaching tactic. Proc Biol Sci 2019; 286:20191135. [PMID: 31311472 PMCID: PMC6661359 DOI: 10.1098/rspb.2019.1135] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Poaching fuelled by international trade in horn caused the deaths of over 1000 African rhinoceros (Ceratotherium simum and Diceros bicornis) per year between 2013 and 2017. Deterrents, which act to establish avoidance behaviours in animals, have the potential to aid anti-poaching efforts by moving at-risk rhinos away from areas of danger (e.g. near perimeter fences). To evaluate the efficacy of deterrents, we exposed a population of southern white rhinos (C. simum simum) to acoustic- (honeybee, siren, turtle dove), olfactory- (chilli, sunflower), and drone-based stimuli on a game reserve in South Africa. We exposed rhinos to each stimulus up to four times. Stimuli were considered effective deterrents if they repeatedly elicited avoidance behaviour (locomotion away from the deterrent). Rhinos travelled significantly further in response to the siren than to the honeybee or turtle dove stimulus, and to low-altitude drone flights than to higher altitude flights. We found the drone to be superior at manipulating rhino movement than the siren owing to its longer transmission range and capability of pursuit. By contrast, the scent stimuli were ineffective at inciting avoidance behaviour. Our findings indicate that deterrents are a prospective low-cost and in situ method to manage rhino movement in game reserves.
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Affiliation(s)
- Samuel G Penny
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK
| | - Rachel L White
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK
| | - Dawn M Scott
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK
| | - Lynne MacTavish
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK
| | - Angelo P Pernetta
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK
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11
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Computer simulation and physical phantom models for estimating the dielectric properties of rhinoceros tissue. PLoS One 2019; 14:e0216595. [PMID: 31141536 PMCID: PMC6541259 DOI: 10.1371/journal.pone.0216595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 04/24/2019] [Indexed: 11/19/2022] Open
Abstract
In vivo and ex vivo sensors have the potential to aid tracking and anti-poaching endeavours and provide new insights into rhinoceros physiology and environment. However, the propagation of electromagnetic signals in rhinoceros tissue is currently not known. We present simulation and agar models of the rhinoceros that allow the investigation of electromagnetic propagation by in vivo and ex vivo devices without the need for surgery. Since the dielectric properties of rhinoceros tissue have not been documented, the conductivity and permittivity of the skin, fat, muscle, blood and other organs are first approximated by means of a meta-analysis that includes animals with similar physical properties. Subsequently, we develop anatomical models that include dermal layers, internal organs and a skeleton. We also develop a flank model that serves as an approximation of the anatomical model in certain situations. These models are used to determine the viability of communication between an in vivo device and an ex vivo device attached to the hind leg of the animal. Two types of antenna (microstrip-fed planar elliptical monopole antenna and printed inverted-F antenna) and three feasible implant locations (back, neck and chest) are considered. In addition to the computer models, phantom recipes using salt, sugar and agar are developed to match the dielectric properties of each tissue type at the industrial, scientific and medical (ISM) frequencies of 403MHz, 910MHz and 2.4GHz. The average error between the measured and theoretically predicted dielectric values was 6.22% over all recipes and 4.49% for the 2.4 GHz recipe specifically. When considering the predicted efficiency of the transmitting and receiving antennas, an agreement of 67.38% was demonstrated between the computer simulations and laboratory measurements using the agar rhinoceros flank models. Computer simulations using the anatomical model of the rhinoceros indicate that the chest is the optimal implant location and that best signal propagation is achieved using the planar inverted-F antenna (PIFA). Using this configuration, the simulations indicate that communication between the implant and an ex vivo device attached to the hind leg is challenging but possible. Furthermore, we find that the inclusion of factors such as the density and temperature of the phantom materials were found to be critical to the achievement of good agreement between practice and simulation.
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White ZW, Vernerey FJ. Armours for soft bodies: how far can bioinspiration take us? BIOINSPIRATION & BIOMIMETICS 2018; 13:041004. [PMID: 29595522 DOI: 10.1088/1748-3190/aababa] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The development of armour is as old as the dawn of civilization. Early man looked to natural structures to harvest or replicate for protection, leaning on millennia of evolutionary developments in natural protection. Since the advent of more modern weaponry, Armor development has seemingly been driven more by materials research than bio-inspiration. However, parallels can still be drawn between modern bullet-protective armours and natural defensive structures. Soft armour for handgun and fragmentation threats can be likened to mammalian skin, and similarly, hard armour can be compared with exoskeletons and turtle shells. Via bio-inspiration, it may be possible to develop structures previously un-researched for ballistic protection. This review will cover current modern ballistic protective structures focusing on energy dissipation and absorption methods, and their natural analogues. As all armour is a compromise between weight, flexibility and protection, the imbricated structure of scaled skin will be presented as a better balance between these factors.
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Affiliation(s)
- Zachary W White
- Mechanical Engineering, University of Colorado Boulder, 427 UCB, Boulder, United States of America
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13
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Grear ME, Motley MR, Crofts SB, Witt AE, Summers AP, Ditsche P. Mechanical properties of harbor seal skin and blubber − a test of anisotropy. ZOOLOGY 2018; 126:137-144. [DOI: 10.1016/j.zool.2017.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Revised: 11/03/2017] [Accepted: 11/03/2017] [Indexed: 01/10/2023]
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14
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Han D, Young BA. The rhinoceros among Serpents: Comparative anatomy and experimental biophysics of Calabar burrowing python (Calabaria reinhardtii
) skin. J Morphol 2017; 279:86-96. [DOI: 10.1002/jmor.20756] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Revised: 09/06/2017] [Accepted: 09/15/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Dawei Han
- Department of Biology; Truman State University; Kirksville Missouri
| | - Bruce A. Young
- Department of Anatomy; Kirksville College of Osteopathic Medicine, A.T. Still University; Kirksville Missouri
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15
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Plochocki JH, Ruiz S, Rodriguez-Sosa JR, Hall MI. Histological study of white rhinoceros integument. PLoS One 2017; 12:e0176327. [PMID: 28441468 PMCID: PMC5404766 DOI: 10.1371/journal.pone.0176327] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/09/2017] [Indexed: 11/19/2022] Open
Abstract
In this study, we report findings from a microscopic analysis of the white rhinoceros (Ceratotherium simum) integumentary ultrastructure. Skin samples from the cheek, shoulder, flank and rump were taken from a 46-year-old female southern white rhinoceros and examined using H&E and elastic histological stains. The epidermis was thickest in the flank (1.003 mm) followed by the rump, cheek and shoulder. The stratum corneum comprised more than half the epidermal thickness. Numerous melanin granules were found in the basal and spinosum layers. The epidermal-dermal junction was characterized by abundant papillary folds increasing surface contact between integument layers. Most of the dermal thickness consisted of organized collagen bundles with scattered elastic fibers. Collagen fiber bundles were thickest in the flank (210.9 μm) followed by shoulder, rump and cheek. Simple coiled sweat glands were present in the dermis, but hair and sebaceous glands were absent. Together, these data suggest the white rhinoceros has a unique integumentary system among large terrestrial herbivores.
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Affiliation(s)
- Jeffrey H. Plochocki
- Department of Anatomy, Midwestern University, Glendale, Arizona, United States of America
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, United States of America
- * E-mail:
| | - Saul Ruiz
- Department of Anatomy, Midwestern University, Glendale, Arizona, United States of America
| | - José R. Rodriguez-Sosa
- Department of Anatomy, Midwestern University, Glendale, Arizona, United States of America
- College of Veterinary Medicine, Midwestern University, Glendale, Arizona, United States of America
| | - Margaret I. Hall
- Department of Anatomy, Midwestern University, Glendale, Arizona, United States of America
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, United States of America
- College of Veterinary Medicine, Midwestern University, Glendale, Arizona, United States of America
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16
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Sherman VR, Tang Y, Zhao S, Yang W, Meyers MA. Structural characterization and viscoelastic constitutive modeling of skin. Acta Biomater 2017; 53:460-469. [PMID: 28219806 DOI: 10.1016/j.actbio.2017.02.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 02/03/2017] [Accepted: 02/07/2017] [Indexed: 10/20/2022]
Abstract
A fascinating material, skin has a tensile response which exhibits an extended toe region of minimal stress up to nominal strains that, in some species, exceed 1, followed by significant stiffening until a roughly linear region. The large toe region has been attributed to its unique structure, consisting of a network of curved collagen fibers. Investigation of the structure of rabbit skin reveals that it consists of layers of wavy fibers, each one with a characteristic orientation. Additionally, the existence of two preferred layer orientations is suggested based on the results of small angle X-ray scattering. These observations are used to construct a viscoelastic model consisting of collagen in two orientations, which leads to an in-plane anisotropic response. The structure-based model presented incorporates the elastic straightening and stretching of fibrils, their rotation towards the tensile axis, and the viscous effects which occur in the matrix of the skin due to interfibrillar and interlamellar sliding. The model is shown to effectively capture key features which dictate the mechanical response of skin. STATEMENT OF SIGNIFICANCE Examination by transmission and scanning electron microscopy of rabbit dermis enabled the identification of the key elements in its structure. The organization of collagen fibrils into flat fibers was identified and incorporated into a constitutive model that reproduces the mechanical response of skin. This enhanced quantitative predictive capability can be used in the design of synthetic skin and skin-like structures.
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17
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Li W, Luo X. An Invariant-Based Damage Model for Human and Animal Skins. Ann Biomed Eng 2016; 44:3109-3122. [PMID: 27066788 PMCID: PMC5042997 DOI: 10.1007/s10439-016-1603-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 03/31/2016] [Indexed: 11/29/2022]
Abstract
Constitutive modelling of skins that account for damage effects is important to provide insight for various clinical applications, such as skin trauma and injury, artificial skin design, skin aging, disease diagnosis, surgery, as well as comparative studies of skin biomechanics between species. In this study, a new damage model for human and animal skins is proposed for the first time. The model is nonlinear, anisotropic, invariant-based, and is based on the Gasser-Ogden-Holzapfel constitutive law initially developed for arteries. Taking account of the mean collagen fibre orientation and its dispersion, the new model can describe a wide range of skins with damage. The model is first tested on the uniaxial test data of human skin and then applied to nine groups of uniaxial test data for the human, swine, rabbit, bovine and rhino skins. The material parameters can be inversely estimated based on uniaxial tests using the optimization method in MATLAB with a root mean square error ranged between 2.15% and 12.18%. A sensitivity study confirms that the fibre orientation dispersion and the mean fibre angle are among the most important factors that influence the behaviour of the damage model. In addition, these two parameters can only be reliably estimated if some histological information is provided. We also found that depending on the location of skins, the tissue damage may be brittle controlled by the fibre breaking limit (i.e., when the fibre stretch is greater than 1.13-1.32, depending on the species), or ductile (due to both the fibre and the matrix damages). The brittle damages seem to occur mostly in the back, and the ductile damages are seen from samples taken from the belly. The proposed constitutive model may be applied to various clinical applications that require knowledge of the mechanical response of human and animal skins.
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Affiliation(s)
- Wenguang Li
- School of Engineering, University of Glasgow, Glasgow, G12 8QQ, UK.
| | - Xiaoyu Luo
- School of Mathematics and Statistics, University of Glasgow, Glasgow, G12 8QW, UK
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Sherman VR, Yang W, Meyers MA. The materials science of collagen. J Mech Behav Biomed Mater 2015; 52:22-50. [PMID: 26144973 DOI: 10.1016/j.jmbbm.2015.05.023] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 05/23/2015] [Accepted: 05/25/2015] [Indexed: 01/22/2023]
Abstract
Collagen is the principal biopolymer in the extracellular matrix of both vertebrates and invertebrates. It is produced in specialized cells (fibroblasts) and extracted into the body by a series of intra and extracellular steps. It is prevalent in connective tissues, and the arrangement of collagen determines the mechanical response. In biomineralized materials, its fraction and spatial distribution provide the necessary toughness and anisotropy. We review the structure of collagen, with emphasis on its hierarchical arrangement, and present constitutive equations that describe its mechanical response, classified into three groups: hyperelastic macroscopic models based on strain energy in which strain energy functions are developed; macroscopic mathematical fits with a nonlinear constitutive response; structurally and physically based models where a constitutive equation of a linear elastic material is modified by geometric characteristics. Viscoelasticity is incorporated into the existing constitutive models and the effect of hydration is discussed. We illustrate the importance of collagen with descriptions of its organization and properties in skin, fish scales, and bone, focusing on the findings of our group.
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Skulborstad AJ, Swartz SM, Goulbourne NC. Biaxial mechanical characterization of bat wing skin. BIOINSPIRATION & BIOMIMETICS 2015; 10:036004. [PMID: 25895436 DOI: 10.1088/1748-3190/10/3/036004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The highly flexible and stretchable wing skin of bats, together with the skeletal structure and musculature, enables large changes in wing shape during flight. Such compliance distinguishes bat wings from those of all other flying animals. Although several studies have investigated the aerodynamics and kinematics of bats, few have examined the complex histology and mechanical response of the wing skin. This work presents the first biaxial characterization of the local deformation, mechanical properties, and fiber kinematics of bat wing skin. Analysis of these data has provided insight into the relationships among the structural morphology, mechanical properties, and functionality of wing skin. Large spatial variations in tissue deformation and non-negligible fiber strains in the cross-fiber direction for both chordwise and spanwise fibers indicate fibers should be modeled as two-dimensional elements. The macroscopic constitutive behavior was anisotropic and nonlinear, with very low spanwise and chordwise stiffness (hundreds of kilopascals) in the toe region of the stress-strain curve. The structural arrangement of the fibers and matrix facilitates a low energy mechanism for wing deployment and extension, and we fabricate examples of skins capturing this mechanism. We propose a comprehensive deformation map for the entire loading regime. The results of this work underscore the importance of biaxial field approaches for soft heterogeneous tissue, and provide a foundation for development of bio-inspired skins to probe the effects of the wing skin properties on aerodynamic performance.
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Affiliation(s)
- A J Skulborstad
- Department of Aerospace Engineering, University of Michigan, FXB Building, 1320 Beal Avenue, Ann Arbor, MI 48109, USA
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Yang W, Sherman VR, Gludovatz B, Schaible E, Stewart P, Ritchie RO, Meyers MA. On the tear resistance of skin. Nat Commun 2015; 6:6649. [PMID: 25812485 PMCID: PMC4389263 DOI: 10.1038/ncomms7649] [Citation(s) in RCA: 184] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 02/12/2015] [Indexed: 01/12/2023] Open
Abstract
Tear resistance is of vital importance in the various functions of skin, especially protection from predatorial attack. Here, we mechanistically quantify the extreme tear resistance of skin and identify the underlying structural features, which lead to its sophisticated failure mechanisms. We explain why it is virtually impossible to propagate a tear in rabbit skin, chosen as a model material for the dermis of vertebrates. We express the deformation in terms of four mechanisms of collagen fibril activity in skin under tensile loading that virtually eliminate the possibility of tearing in pre-notched samples: fibril straightening, fibril reorientation towards the tensile direction, elastic stretching and interfibrillar sliding, all of which contribute to the redistribution of the stresses at the notch tip. It is known that skin has a large tear resistance, but little is known of the mechanism behind this. Here, the authors carry out a structural analysis of rabbit skin to show how the deformation of collagen fibrils in the skin results in a strong resistance to tear propagation.
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Affiliation(s)
- Wen Yang
- Materials Science and Engineering Program, University of California, San Diego, California 92093, USA
| | - Vincent R Sherman
- Materials Science and Engineering Program, University of California, San Diego, California 92093, USA
| | - Bernd Gludovatz
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Eric Schaible
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Polite Stewart
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Robert O Ritchie
- 1] Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
| | - Marc A Meyers
- 1] Materials Science and Engineering Program, University of California, San Diego, California 92093, USA [2] Department of Mechanical and Aerospace Engineering, University of California, San Diego, California 92093, USA [3] Department of NanoEngineering, University of California, San Diego, California 92093, USA
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Sathar F, Ludo Badlangana N, Manger PR. Variations in the Thickness and Composition of the Skin of the Giraffe. Anat Rec (Hoboken) 2010; 293:1615-27. [DOI: 10.1002/ar.21190] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Farzana Sathar
- Faculty of Health Sciences, School of Anatomical Sciences,University of the Witwatersrand, Parktown, Johannesburg, Republic of South Africa
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Hieronymus TL, Witmer LM, Tanke DH, Currie PJ. The Facial Integument of Centrosaurine Ceratopsids: Morphological and Histological Correlates of Novel Skin Structures. Anat Rec (Hoboken) 2009; 292:1370-96. [DOI: 10.1002/ar.20985] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Manning PL, Morris PM, McMahon A, Jones E, Gize A, Macquaker JHS, Wolff G, Thompson A, Marshall J, Taylor KG, Lyson T, Gaskell S, Reamtong O, Sellers WI, van Dongen BE, Buckley M, Wogelius RA. Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA). Proc Biol Sci 2009; 276:3429-37. [PMID: 19570788 DOI: 10.1098/rspb.2009.0812] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).
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Affiliation(s)
- Phillip L Manning
- School of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, UK
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Chen PY, Lin AYM, Lin YS, Seki Y, Stokes AG, Peyras J, Olevsky EA, Meyers MA, McKittrick J. Structure and mechanical properties of selected biological materials. J Mech Behav Biomed Mater 2008. [PMID: 19627786 DOI: 10.1016/j.pmatsci.2007.05.002] [Citation(s) in RCA: 950] [Impact Index Per Article: 59.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
Mineralized biological tissues offer insight into how nature has evolved these components to optimize multifunctional purposes. These mineral constituents are weak by themselves, but interact with the organic matrix to produce materials with unexpected mechanical properties. The hierarchical structure of these materials is at the crux of this enhancement. Microstructural features such as organized, layered organic/inorganic structures and the presence of porous and fibrous elements are common in many biological components. The organic and inorganic portions interact at the molecular and micro-levels synergistically to enhance the mechanical function. In this paper, we report on recent progress on studies of the abalone and Araguaia river clam shells, arthropod exoskeletons, antlers, tusks, teeth and bird beaks.
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Affiliation(s)
- P-Y Chen
- Materials Science and Engineering Program, UC San Diego, La Jolla, CA 92037-0411, United States
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Vincent J. Defense and Attack Strategies and Mechanisms in Biology. Biomimetics (Basel) 2005. [DOI: 10.1201/9781420037715.ch13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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