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Iyer D, Laws E, LaJeunesse D. Escherichia coli Adhesion and Biofilm Formation on Polymeric Nanostructured Surfaces. ACS OMEGA 2023; 8:47520-47529. [PMID: 38144076 PMCID: PMC10734028 DOI: 10.1021/acsomega.3c04747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 09/25/2023] [Indexed: 12/26/2023]
Abstract
Biofilm formation is a multistep process that requires initial contact between a bacterial cell and a surface substrate. Recent work has shown that nanoscale topologies impact bacterial cell viability; however, less is understood about how nanoscale surface properties impact other aspects of bacterial behavior. In this study, we examine the adhesive, viability, morphology, and colonization behavior of the bacterium Escherichia coli on 21 plasma-etched polymeric surfaces. Although we predicted that specific nanoscale surface structures of the surface would control specific aspects of bacterial behavior, we observed no correlation between any bacterial response or surface structures/properties. Instead, it appears that the surface composition of the polymer plays the most significant role in controlling and determining a bacterial response to a substrate, although changes to a polymeric surface via plasma etching alter initial bacteria colonization and morphology.
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Affiliation(s)
- Divya Iyer
- Department of Nanoscience,
Joint School of Nanoscience and Nanoengineering, University of North Carolina Greensboro, 2907 East Lee Street, Greensboro, North Carolina 27455, United States
| | - Eric Laws
- Department of Nanoscience,
Joint School of Nanoscience and Nanoengineering, University of North Carolina Greensboro, 2907 East Lee Street, Greensboro, North Carolina 27455, United States
| | - Dennis LaJeunesse
- Department of Nanoscience,
Joint School of Nanoscience and Nanoengineering, University of North Carolina Greensboro, 2907 East Lee Street, Greensboro, North Carolina 27455, United States
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2
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Yoshida K, Katsurashima Y, Takahashi L. Analysis of Surface Patterns and Electric Field Simulation of Antireflective Green Lacewing Wings. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:3098-3104. [PMID: 35245075 DOI: 10.1021/acs.langmuir.1c02962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The structural coloration and decoloration are problems of scientific interest for a long time. Hence, the fundamental investigations on structures and the optical properties of insect wings have been performed. As a part of such studies, we elucidate the optical properties of green lacewing wings via observation and simulation. First, we elucidate the surface pattern of green lacewing wings using a two-dimensional fast Fourier transform. A cross-shaped pattern of a Fourier spectrum is obtained, and the concise wing model with the surface protrusions arranged in a square grid on a base substrate is constructed in reference to the obtained Fourier spectrum. Next, we perform a finite-difference time-domain (FDTD) simulation to elucidate a light path through wings with and without surface protrusions. The FDTD simulation results indicate that the surface protrusions of a wing increase and decrease the intensity of the transmitted and reflected light, respectively, which is an antireflection behavior. This phenomenon was also observed in the case of 45° incident light. The intensity of transmitted light coupled to wings is induced by surface protrusions with a stepwise refractive index between air and a substrate, which induces antireflection. In particular, transmitted light is increased by the surface protrusions of wings in the range of 500-800 nm wavelength. The intensities of transmitted and reflected light are affected by the direction of incident electric field (polarization) in the case of wings with protrusions arranged in the same direction (parallel). Hence, the surface protrusions are arranged in a square grid to reduce the influence of the polarization direction.
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Affiliation(s)
- Kazunari Yoshida
- Graduate School of Science and Engineering,Yamagata University, 4-3-16 Jonan, Yonezawa-shi, Yamagata 992-8510, Japan
| | - Yuro Katsurashima
- Graduate School of Science and Engineering,Yamagata University, 4-3-16 Jonan, Yonezawa-shi, Yamagata 992-8510, Japan
| | - Leona Takahashi
- College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa 252-5258, Japan
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3
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Perumanath S, Borg MK, Sprittles JE, Enright R. Molecular physics of jumping nanodroplets. NANOSCALE 2020; 12:20631-20637. [PMID: 32776062 DOI: 10.1039/d0nr03766d] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Next-generation processor-chip cooling devices and self-cleaning surfaces can be enhanced by a passive process that requires little to no electrical input, through coalescence-induced nanodroplet jumping. Here, we describe the crucial impact thermal capillary waves and ambient gas rarefaction have on enhancing/limiting the jumping speeds of nanodroplets on low adhesion surfaces. By using high-fidelity non-equilibrium molecular dynamics simulations in conjunction with well-resolved volume-of-fluid continuum calculations, we are able to quantify the different dissipation mechanisms that govern nanodroplet jumping at length scales that are currently difficult to access experimentally. We find that interfacial thermal capillary waves contribute to a large statistical spread of nanodroplet jumping speeds that range from 0-30 m s-1, where the typical jumping speeds of micro/millimeter sized droplets are only up to a few m s-1. As the gas surrounding these liquid droplets is no longer in thermodynamic equilibrium, we also show how the reduced external drag leads to increased jumping speeds. This work demonstrates that, in the viscous-dominated regime, the Ohnesorge number and viscosity ratio between the two phases alone are not sufficient, but that the thermal fluctuation number (Th) and the Knudsen number (Kn) are both needed to recover the relevant molecular physics at nanoscales. Our results and analysis suggest that these dimensionless parameters would be relevant for many other free-surface flow processes and applications that operate at the nanoscale.
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Affiliation(s)
| | - Matthew K Borg
- School of Engineering, University of Edinburgh, Edinburgh EH9 3FB, UK
| | | | - Ryan Enright
- Thermal Management Research Group, ηET Dept., Nokia Bell Labs, Dublin D15 Y6NT, Ireland.
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Yoshida K, Takahashi L, Takashima A, Fujii Y, Nishio I. Antireflection in Green Lacewing Wings with Random Height Surface Protrusions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:4207-4213. [PMID: 32227849 DOI: 10.1021/acs.langmuir.9b03714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Wings of insects exhibit many functions apart from flying. In particular, their antireflection function is important for insects to avoid detection by their enemies. This function can be applied to antireflection biomimetic films in engineering fields. For such applications, confirming the antireflection mechanisms of insect wings is important. Herein, we used electron microscopy to compare the surfaces of green lacewing wings with and without a surface wax structure and recorded the transmittance spectra to clarify the surface structural and optical properties of insect wings. The spectral transmittance was higher for wings with a surface wax structure than for wings without a wax layer in the light wavelength regime from 500 to 750 nm. We constructed a concise model of the green lacewing wing with flake-like surface structure with a graded effective refractive index corresponding to the wing samples with a surface wax layer; we also constructed a simple thin-film model corresponding to the wing samples without a wax layer. The graded refractive indices were calculated using the effective medium theory, and the transmittance spectra of such models were then calculated using the transfer-matrix method. It was observed that the calculated spectra are in good agreement with the experimental results. In addition, wing samples without a surface structure induce thin-film interference. These results suggest that a wax structure can reduce the reflectance and increase the transmittance enabling the green lacewings to avoid detection by their enemies. These findings may lead to further advances in both the biomimetic field and fundamental research fields.
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Affiliation(s)
- Kazunari Yoshida
- Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan
| | - Leona Takahashi
- College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Saganihara, Kanagawa 252-5258, Japan
| | - Akito Takashima
- College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Saganihara, Kanagawa 252-5258, Japan
| | - Yasuhiro Fujii
- College of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan
| | - Izumi Nishio
- College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Saganihara, Kanagawa 252-5258, Japan
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6
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Morphological and histological study of the forewing of Aleyrodes proletella (Linnaeus 1758) (Sternorrhyncha, Hemiptera) with a comparative analysis of forewings among Sternorrhyncha infraorders. ZOOMORPHOLOGY 2019. [DOI: 10.1007/s00435-019-00449-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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7
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Joel AC, Weissbach M. Same Principles but Different Purposes: Passive Fluid Handling throughout the Animal Kingdom. Integr Comp Biol 2019; 59:1673-1680. [DOI: 10.1093/icb/icz018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Abstract
Everything on earth is subject to physical laws, thus they influence all facets of living creatures. Although these laws restrain animals in many ways, some animals have developed a way to use physical phenomena in their favor to conserve energy. Many animals, which have to handle fluids, for example, have evolved passive mechanisms by adapting their wettability or using capillary forces for rapid fluid spreading. In distinct animals, a similar selection pressure always favors a convergent development. However, when assessing the biological tasks of passive fluid handling mechanisms, their diversity is rather surprising. Besides the well-described handling of water to facilitate drinking in arid regions, observed in, e.g., several lizards, other animals like a special flat bug have developed a similar mechanism for a completely different task and fluid: Instead of water, these bugs passively transport an oily defense secretion to a region close to their head where it finally evaporates. And again some spiders use capillary forces to capture prey, by sucking in the viscous waxy cuticle of their prey with their nanofibrous threads. This review highlights the similarities and differences in the deployed mechanisms of passive fluid handling across the animal kingdom. Besides including well-studied animals to point out different mechanisms in general, we stretch over to not as extensively studied species for which similar mechanisms are described for different tasks. Thus, we provide an extensive overview of animals for which passive fluid handling is described so far as well as for future inspiration.
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Affiliation(s)
- Anna-Christin Joel
- Institute of Zoology, RWTH Aachen University, Worringerweg 3, Aachen, Germany
| | - Margret Weissbach
- Institute of Zoology, RWTH Aachen University, Worringerweg 3, Aachen, Germany
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Perumanath S, Borg MK, Chubynsky MV, Sprittles JE, Reese JM. Droplet Coalescence is Initiated by Thermal Motion. PHYSICAL REVIEW LETTERS 2019; 122:104501. [PMID: 30932677 DOI: 10.1103/physrevlett.122.104501] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 09/11/2018] [Indexed: 06/09/2023]
Abstract
The classical notion of the coalescence of two droplets of the same radius R is that surface tension drives an initially singular flow. In this Letter we show, using molecular dynamics simulations of coalescing water nanodroplets, that after single or multiple bridges form due to the presence of thermal capillary waves, the bridge growth commences in a thermal regime. Here, the bridges expand linearly in time much faster than the viscous-capillary speed due to collective molecular jumps near the bridge fronts. Transition to the classical hydrodynamic regime only occurs once the bridge radius exceeds a thermal length scale l_{T}∼sqrt[R].
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Affiliation(s)
- Sreehari Perumanath
- School of Engineering, University of Edinburgh, Edinburgh EH9 3FB, United Kingdom
| | - Matthew K Borg
- School of Engineering, University of Edinburgh, Edinburgh EH9 3FB, United Kingdom
| | - Mykyta V Chubynsky
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - James E Sprittles
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Jason M Reese
- School of Engineering, University of Edinburgh, Edinburgh EH9 3FB, United Kingdom
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9
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Gao Y, Xiang Q, Wang Y, Men Y, Yang X, Wang Q, Yang Z, Geng X. Microstructures and grease layer of water strider and its influence on superhydrophobicity. BIOINSPIRED BIOMIMETIC AND NANOBIOMATERIALS 2018. [DOI: 10.1680/jbibn.17.00008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
In this paper, the microstructures of the water strider surface were observed by scanning electron microscopy. The surfaces, including wings, legs, back and abdomen, all exhibited various compound microstructures, which are the important factors influencing the superhydrophobicity with a contact angle (CA) of up to 153°. Furthermore, the grease of the water strider on different substrates was studied by self-assembly of the grease for 14 d. Images of the grease indicated that the morphology and spatial orientation of the grease depend on the substrate chosen. The grease decreased the substrate wettability by approximately 30° on highly ordered pyrolytic graphite and about 23° on the silicon substrates. Gas chromatography combined with mass spectrometry was also used to study the chemical composition of the grease layer of water strider surface. The grease layer is composed of a mixture of aliphatic compounds, which possess hydrophobicity based on the chemical structure. Grease protects the microstructures of water strider surfaces and thus results in higher CAs and hydrophobic properties. The microstructure and the grease of the water strider jointly render the hydrophobic properties of the water strider surface.
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Affiliation(s)
- Ying Gao
- Changchun Institute of Technology, Changchun, China
| | - Qian Xiang
- Changchun Institute of Technology, Changchun, China
| | - Yi Wang
- Changchun Institute of Technology, Changchun, China
| | - Yuzhuo Men
- Changchun Institute of Technology, Changchun, China
| | - Xiaodong Yang
- Jilin Engineering Normal University, Changchun, China
| | | | - Zhuojuan Yang
- Jilin Engineering Normal University, Changchun, China
| | - Xiaohui Geng
- Changchun Institute of Technology, Changchun, China
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10
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Vahabi H, Wang W, Davies S, Mabry JM, Kota AK. Coalescence-Induced Self-Propulsion of Droplets on Superomniphobic Surfaces. ACS APPLIED MATERIALS & INTERFACES 2017; 9:29328-29336. [PMID: 28771317 DOI: 10.1021/acsami.7b09344] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We utilized superomniphobic surfaces to systematically investigate the different regimes of coalescence-induced self-propulsion of liquid droplets with a wide range of droplet radii, viscosities, and surface tensions. Our results indicate that the nondimensional jumping velocity Vj* is nearly constant (Vj* ≈ 0.2) in the inertial-capillary regime and decreases in the visco-capillary regime as the Ohnesorge number Oh increases, in agreement with prior work. Within the visco-capillary regime, decreasing the droplet radius R0 results in a more rapid decrease in the nondimensional jumping velocity Vj* compared to increasing the viscosity μ. This is because decreasing the droplet radius R0 increases the inertial-capillary velocity Vic in addition to increasing the Ohnesorge number Oh.
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Affiliation(s)
| | | | | | - Joseph M Mabry
- Rocket Propulsion Division, Air Force Research Laboratory , Edwards AFB, California 93524, United States
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11
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Sun M, Chen Y, Zheng Y, Zhen M, Shu C, Dai Z, Liang A, Gorb SN. Wettability gradient on the elytra in the aquatic beetle Cybister chinensis and its role in angular position of the beetle at water-air interface. Acta Biomater 2017; 51:408-417. [PMID: 28069503 DOI: 10.1016/j.actbio.2017.01.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 12/13/2016] [Accepted: 01/05/2017] [Indexed: 11/19/2022]
Abstract
The surface of the elytra in some species of aquatic beetles displays relatively low contact angles (CAs), even showing hydrophilic properties. In this study, we report on an observation that both sexes of Cybister chinensis beetle fresh elytral surface do not exhibit uniform CA, but rather a wettability gradient along the longitudinal axis in posterior direction. The wettability is very different between females and males due to the presence (female) or absence (male) of channels on the elytral surface. When a small drop of water touches the elytra surface, it tends to slide towards the anterior having a lower CA on the elytra. This gradient presumably supports a breathing-associated behavior of beetles in which they cause the tip of their abdomen to protrude into the surface of the water in order to collect an air bubble for oxygen uptake and, when floating on the surface, to keep the body inclined at a small angle to the water's surface with their heads immersed. STATEMENT OF SIGNIFICANCE Hydrophobicity on surfaces is a fundamental property which has attracted great interest across all scientific disciplines, here we have demonstrated that the gradually changing chemistry of the elytral surface facilitates the tilted beetle posture on the water's surface. The mechanism of water interacting with the elytra demonstrated the most energetically favorable posture in the diving beetles. Surfaces with directional wetting properties that promote droplet drainage are of significant practical importance in many fields. The anisotropic topography and wetting properties of the elytra may inspire microfluidic devices for medical and robotic applications.
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Affiliation(s)
- Mingxia Sun
- Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beichen West Road 1-5, Chaoyang District, Beijing 1000101, China; Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany.
| | - Yuan Chen
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Xueyuan Road 37, Haidian District, Beijing 100191, China.
| | - Yongmei Zheng
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Xueyuan Road 37, Haidian District, Beijing 100191, China.
| | - Mingming Zhen
- Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street 2, Haidian District, Beijing 100190, China.
| | - Chunying Shu
- Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street 2, Haidian District, Beijing 100190, China.
| | - Zhendong Dai
- Institute of Bio-inspired Structure and Surface Engineering, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing 210016, China.
| | - Aiping Liang
- Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beichen West Road 1-5, Chaoyang District, Beijing 1000101, China.
| | - Stanislav N Gorb
- Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany.
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Watson GS, Watson JA, Cribb BW. Diversity of Cuticular Micro- and Nanostructures on Insects: Properties, Functions, and Potential Applications. ANNUAL REVIEW OF ENTOMOLOGY 2017; 62:185-205. [PMID: 28141960 DOI: 10.1146/annurev-ento-031616-035020] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Insects exhibit a fascinating and diverse range of micro- and nanoarchitectures on their cuticle. Beyond the spectacular beauty of such minute structures lie surfaces evolutionarily modified to act as multifunctional interfaces that must contend with a hostile, challenging environment, driving adaption so that these can then become favorable. Numerous cuticular structures have been discovered this century; and of equal importance are the properties, functions, and potential applications that have been a key focus in many recent studies. The vast range of insect structuring, from the most simplistic topographies to the most elegant and geometrically complex forms, affords us with an exhaustive library of natural templates and free technologies to borrow, replicate, and employ for a range of applications. Of particular importance are structures that imbue cuticle with antiwetting properties, self-cleaning abilities, antireflection, enhanced color, adhesion, and antimicrobial and specific cell-attachment properties.
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Affiliation(s)
- Gregory S Watson
- School of Science and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland 4556, Australia; ,
| | - Jolanta A Watson
- School of Science and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland 4556, Australia; ,
| | - Bronwen W Cribb
- Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland 4072, Australia;
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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Hidden surface microstructures on Carboniferous insect Brodioptera sinensis (Megasecoptera) enlighten functional morphology and sensorial perception. Sci Rep 2016; 6:28316. [PMID: 27321551 PMCID: PMC4913241 DOI: 10.1038/srep28316] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 06/01/2016] [Indexed: 11/09/2022] Open
Abstract
Megasecoptera are insects with haustellate mouthparts and petiolate wings closely related to Palaeodictyoptera and one of the few insect groups that didn’t survive the Permian-Triassic mass extinction. Recent discovery of Brodioptera sinensis in early Pennsylvanian deposits at Xiaheyan in northern China has increased our knowledge of its external morphology using conventional optical stereomicroscopy. Environmental scanning electron microscopy (ESEM) of structures, such as antennae, mouthparts, wing surfaces, external copulatory organs and cerci have shed light on their micromorphology and supposed function. A comparative study has shown an unexpected dense pattern of setae on the wing membrane of B. sinensis. In addition, unlike the results obtained by stereomicroscopy it revealed that the male and female external genitalia clearly differ in their fine structure and setation. Therefore, the present study resulted in a closer examination of the microstructure and function of previously poorly studied parts of the body of Paleozoic insects and a comparison with homologous structures occurring in other Palaeodictyopteroida, Odonatoptera and Ephemerida. This indicates, that the role and presumptive function of these integumental protuberances is likely to have been a sensory one in the coordination of mouthparts and manipulation of stylets, escape from predators, enhancement of aerodynamic properties and copulatory behaviour.
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Watson GS, Cribb BW, Schwarzkopf L, Watson JA. Contaminant adhesion (aerial/ground biofouling) on the skin of a gecko. J R Soc Interface 2016; 12:20150318. [PMID: 26063826 DOI: 10.1098/rsif.2015.0318] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In this study, we have investigated the micro- and nano-structuring and contaminant adhesional forces of the outer skin layer of the ground dwelling gecko--Lucasium steindachneri. The lizard's skin displayed a high density of hairs with lengths up to 4 μm which were spherically capped with a radius of curvature typically less than 30 nm. The adhesion of artificial hydrophilic (silica) and hydrophobic (C18) spherical particles and natural pollen grains were measured by atomic force microscopy and demonstrated extremely low values comparable to those recorded on superhydrophobic insects. The lizard scales which exhibited a three-tier hierarchical architecture demonstrated higher adhesion than the trough regions between scales. The two-tier roughness of the troughs comprising folding of the skin (wrinkling) limits the number of contacting hairs with particles of the dimensions used in our study. The gecko skin architecture on both the dorsal and trough regions demonstrates an optimized topography for minimizing solid-solid and solid-liquid particle contact area, as well as facilitating a variety of particulate removal mechanisms including water-assisted processes. These contrasting skin topographies may also be optimized for other functions such as increased structural integrity, levels of wear protection and flexibility of skin for movement and growth. While single hair adhesion is low, contributions of many thousands of individual hairs (especially on the abdominal scale surface and if deformation occurs) may potentially aid in providing additional adhesional capabilities (sticking ability) for some gecko species when interacting with environmental substrates such as rocks, foliage and even man-made structuring.
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Affiliation(s)
- Gregory S Watson
- School of Science and Engineering, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
| | - Bronwen W Cribb
- Centre for Microscopy and Microanalysis and School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Lin Schwarzkopf
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia
| | - Jolanta A Watson
- School of Science and Engineering, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
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Chandran R, Williams L, Hung A, Nowlin K, LaJeunesse D. SEM characterization of anatomical variation in chitin organization in insect and arthropod cuticles. Micron 2015; 82:74-85. [PMID: 26774746 DOI: 10.1016/j.micron.2015.12.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/23/2015] [Accepted: 12/23/2015] [Indexed: 01/18/2023]
Abstract
The cuticles of insects and arthropods have some of the most diverse material properties observed in nature, so much so that it is difficult to imagine that all cutciles are primarily composed of the same two materials: a fibrous chitin network and a matrix composed of cuticle proteins. Various factors contribute to the mechanical and optical properties of an insect or arthropod cuticle including the thickness and composition. In this paper, we also identified another factor that may contribute to the optical, surface, and mechanical properties of a cuticle, i.e. the organization of chitin nanofibers and chitin fiber bundles. Self-assembled chitin nanofibers serve as the foundation for all higher order chitin structures in the cuticles of insects and other arthropods via interactions with structural cuticle proteins. Using a technique that enables the characterization of chitin organization in the cuticle of intact insects and arthropod exoskeletons, we demonstrate a structure/function correlation of chitin organization with larger scale anatomical structures. The chitin scaffolds in cuticles display an extraordinarily diverse set of morphologies that may reflect specific mechanical or physical properties. After removal of the proteinaceous and mineral matrix of a cuticle, we observe using SEM diverse nanoscale and micro scale organization of in-situ chitin in the wing, head, eye, leg, and dorsal and ventral thoracic regions of the periodical cicada Magicicada septendecim and in other insects and arthropods. The organization of chitin also appears to have a significant role in the organization of nanoscale surface structures. While microscale bristles and hairs have long been known to be chitin based materials formed as cellular extensions, we have found a nanostructured layer of chitin in the cuticle of the wing of the dog day annual cicada Tibicen tibicens, which may be the scaffold for the nanocone arrays found on the wing. We also use this process to examine the chitin organizations in the fruit fly, Drosophila melanogaster, and the Atlantic brown shrimp, Farfantepenaeus aztecus. Interestingly many of the homologous anatomical structures from diverse arthropods exhibit similar patterns of chitin organization suggesting that a common set of parameters, govern chitin organization.
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Affiliation(s)
- Rakkiyappan Chandran
- Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina Greensboro, 2907 East Gate City Blvd., Greensboro, NC 27401, United States
| | - Lee Williams
- Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina Greensboro, 2907 East Gate City Blvd., Greensboro, NC 27401, United States
| | - Albert Hung
- Department of Nanoengineering, Joint School of Nanoscience and Nanoengineering, North Carolina A&T State University, 2907 East Gate City Blvd., Greensboro, NC 27401, United States
| | - Kyle Nowlin
- Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina Greensboro, 2907 East Gate City Blvd., Greensboro, NC 27401, United States
| | - Dennis LaJeunesse
- Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina Greensboro, 2907 East Gate City Blvd., Greensboro, NC 27401, United States.
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Watson GS, Schwarzkopf L, Cribb BW, Myhra S, Gellender M, Watson JA. Removal mechanisms of dew via self-propulsion off the gecko skin. J R Soc Interface 2015; 12:rsif.2014.1396. [PMID: 25762647 DOI: 10.1098/rsif.2014.1396] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Condensation resulting in the formation of water films or droplets is an unavoidable process on the cuticle or skin of many organisms. This process generally occurs under humid conditions when the temperature drops below the dew point. In this study, we have investigated dew conditions on the skin of the gecko Lucasium steindachneri. When condensation occurs, we show that small dew drops, as opposed to a thin film, form on the lizard's scales. As the droplets grow in size and merge, they can undergo self-propulsion off the skin and in the process can be carried away a sufficient distance to freely engage with external forces. We show that factors such as gravity, wind and fog provide mechanisms to remove these small droplets off the gecko skin surface. The formation of small droplets and subsequent removal from the skin may aid in reducing microbial contact (e.g. bacteria, fungi) and limit conducive growth conditions under humid environments. As well as providing an inhospitable microclimate for microorganisms, the formation and removal of small droplets may also potentially aid in other areas such as reduction and cleaning of some surface contaminants consisting of single or multiple aggregates of particles.
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Affiliation(s)
- Gregory S Watson
- School of Science and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
| | - Lin Schwarzkopf
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia
| | - Bronwen W Cribb
- Centre for Microscopy and Microanalysis and School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Sverre Myhra
- The University of Oxford, Begbroke Science Park, Sandy Lane, Yarnton OX5 1PF, UK
| | - Marty Gellender
- Previously Queensland Department of Environment and Heritage Protection, GPO Box 2454, Brisbane, Queensland 4001, Australia
| | - Jolanta A Watson
- School of Science and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
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Watson GS, Green DW, Schwarzkopf L, Li X, Cribb BW, Myhra S, Watson JA. A gecko skin micro/nano structure - A low adhesion, superhydrophobic, anti-wetting, self-cleaning, biocompatible, antibacterial surface. Acta Biomater 2015; 21:109-22. [PMID: 25772496 DOI: 10.1016/j.actbio.2015.03.007] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 02/17/2015] [Accepted: 03/05/2015] [Indexed: 12/21/2022]
Abstract
Geckos, and specifically their feet, have attracted significant attention in recent times with the focus centred around their remarkable adhesional properties. Little attention however has been dedicated to the other remaining regions of the lizard body. In this paper we present preliminary investigations into a number of notable interfacial properties of the gecko skin focusing on solid and aqueous interactions. We show that the skin of the box-patterned gecko (Lucasium sp.) consists of dome shaped scales arranged in a hexagonal patterning. The scales comprise of spinules (hairs), from several hundred nanometres to several microns in length, with a sub-micron spacing and a small radius of curvature typically from 10 to 20 nm. This micro and nano structure of the skin exhibited ultralow adhesion with contaminating particles. The topography also provides a superhydrophobic, anti-wetting barrier which can self clean by the action of low velocity rolling or impacting droplets of various size ranges from microns to several millimetres. Water droplets which are sufficiently small (10-100 μm) can easily access valleys between the scales for efficient self-cleaning and due to their dimensions can self-propel off the surface enhancing their mobility and cleaning effect. In addition, we demonstrate that the gecko skin has an antibacterial action where Gram-negative bacteria (Porphyromonas gingivalis) are killed when exposed to the surface however eukaryotic cell compatibility (with human stem cells) is demonstrated. The multifunctional features of the gecko skin provide a potential natural template for man-made applications where specific control of liquid, solid and biological contacts is required.
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Ye X, Bhushan B, Zhou M, Lei W. The surface microstructure of cusps and leaflets in rabbit and mouse heart valves. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2014; 5:622-629. [PMID: 24991498 PMCID: PMC4077300 DOI: 10.3762/bjnano.5.73] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 04/17/2014] [Indexed: 06/03/2023]
Abstract
In this investigation, scanning electron microscopy was used to characterize the microstructure on the surfaces of animal heart valve cusps/leaflets. The results showed that though these surfaces appear smooth to the naked eye, they are actually comprised of a double hierarchical structure consisting of a cobblestone-like microstructure and nano-cilia along with mastoids with a directional arrangement. Such nanostructures could play a very important role in the hemocompatibility characteristics of heart valves. On this basis, the model of the microstructure was constructed and theoretical analysis was used to obtain optimal geometric parameters for the rough surface of artificial valve cusps/leaflets. This model may help improve reconstructive techniques and it may be beneficial in the design and fabrication of valve substitutes or partial substitutes. Namely, the model may help ameliorate heart valve replacement surgery.
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Affiliation(s)
- Xia Ye
- School of Mechanical Engineering, Jiangsu University of Technology, Changzhou Jiangsu 213001, China
| | - Bharat Bhushan
- Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics (NLB2), The Ohio State University, 201 W 19th Ave., Columbus, OH 43210, USA
| | - Ming Zhou
- Center of Photonics Fabrication, Jiangsu University, Zhenjiang Jiangsu 212013, China
| | - Weining Lei
- School of Mechanical Engineering, Jiangsu University of Technology, Changzhou Jiangsu 213001, China
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Watson GS, Gellender M, Watson JA. Self-propulsion of dew drops on lotus leaves: a potential mechanism for self cleaning. BIOFOULING 2014; 30:427-34. [PMID: 24628521 DOI: 10.1080/08927014.2014.880885] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
This study shows that condensation on the hierarchically structured lotus leaf can facilitate self-propulsion of water droplets off the surface. Droplets on leaves inclined at high angles can be completely removed from the surface by self-propulsion with the assistance of gravity. Due to the small size of mobile droplets, light breezes may also fully remove the propelled droplets, which are typically projected beyond the boundary layer of the leaf cuticle. Moreover the self-propelled droplets/condensate were able to remove contaminants (eg silica particles) from the leaf surface. The biological significance of this process may be associated with maintaining a healthy cuticle surface when the action of rain to clean the surface via the lotus effect is not possible (due to no precipitation). Indeed, the native lotus plants in this study were located in a region with extended time periods (several months) without rain. Thus, dew formation on the leaf may provide an alternative self-cleaning mechanism during times of drought and optimise the functional efficiency of the leaf surface as well as protecting the surface from long term exposure to pathogens such as bacteria and fungi.
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Affiliation(s)
- Gregory S Watson
- a School of Marine and Tropical Biology , James Cook University , Townsville , Australia
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Abstract
The microstructures on elytral surface of aquatic beetles belonging to Hydrophilidae and Dytiscidae were observed under an environment scanning microscope, and the wettabilities were determined with an optical contact angle meter. The results show the elytral surfaces are relatively smooth compared to the structures of other insects such as the butterfly wing scales or cicada wing protrusions. They exhibit a polygonal structuring with grooves and pores being the main constituent units. The contact angles (CAs) range from 47.1oto 82.1o. The advancing and receding angles were measured by injecting into and withdrawing a small amount of water on the most hydrophilic (with a contact angle of 47.1o) and hydrophobic (with a contact angle of 82.1o) elytral surfaces, which illustrates the vital role of three-phase contact line (TCL) in the wetting mechanism of aquatic beetle elytral surfaces.
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Self-cleaning of superhydrophobic surfaces by self-propelled jumping condensate. Proc Natl Acad Sci U S A 2013; 110:7992-7. [PMID: 23630277 DOI: 10.1073/pnas.1210770110] [Citation(s) in RCA: 251] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The self-cleaning function of superhydrophobic surfaces is conventionally attributed to the removal of contaminating particles by impacting or rolling water droplets, which implies the action of external forces such as gravity. Here, we demonstrate a unique self-cleaning mechanism whereby the contaminated superhydrophobic surface is exposed to condensing water vapor, and the contaminants are autonomously removed by the self-propelled jumping motion of the resulting liquid condensate, which partially covers or fully encloses the contaminating particles. The jumping motion off the superhydrophobic surface is powered by the surface energy released upon coalescence of the condensed water phase around the contaminants. The jumping-condensate mechanism is shown to spontaneously clean superhydrophobic cicada wings, where the contaminating particles cannot be removed by gravity, wing vibration, or wind flow. Our findings offer insights for the development of self-cleaning materials.
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Sun M, Liang A, Watson GS, Watson JA, Zheng Y, Jiang L. Compound microstructures and wax layer of beetle elytral surfaces and their influence on wetting properties. PLoS One 2012; 7:e46710. [PMID: 23056414 PMCID: PMC3464267 DOI: 10.1371/journal.pone.0046710] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Accepted: 09/03/2012] [Indexed: 11/18/2022] Open
Abstract
A beetles' first line of defense against environmental hazards is their mesothoracic elytra--rigid, protective forewings. In order to study the interaction of these wings with water, the surface microstructures of various beetles' elytra were observed by Environment Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM). Chemistry components were ascertained using X-ray photoelectron spectroscopy (XPS). All the beetles of various habitats (including desert, plant, dung, land and water) exhibited compound microstructures on their elytra. The wetting properties of these elytra were identified using an optical contact angle meter. In general the native elytra exhibited hydrophilic or weak hydrophobic properties with contact angles (CAs) ranging from 47.5° to 109.1°. After treatment with chloroform, the CAs all increased on the rougher elytral surfaces. The presence of wax is not the only determinant of hydrophobic properties, but rather a combination with microscopic structures found on the surfaces. Irregularities and the presence or absence of tiny cracks, hairs (or setae), pores and protrusions are important factors which influence the wetting properties. Rougher elytral surfaces tended to present a stronger hydrophobicity. Effects on hydrophobicity, such as surface microstructures, chemistry, environment and aging (referring to the time after emergence), are also included and discussed. Our results also provide insights into the motion of water droplets when in contact with beetle elytra.
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Affiliation(s)
- Mingxia Sun
- Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Aiping Liang
- Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Gregory S. Watson
- Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Townsville, Australia
- School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Australia
| | - Jolanta A. Watson
- Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Townsville, Australia
- School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Australia
| | - Yongmei Zheng
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Beijing, People’s Republic of China
| | - Lei Jiang
- Center of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, People’s Republic of China
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Sun M, Liang A, Watson GS, Watson JA, Zheng Y, Ju J, Jiang L. Influence of cuticle nanostructuring on the wetting behaviour/states on cicada wings. PLoS One 2012; 7:e35056. [PMID: 22536351 PMCID: PMC3335046 DOI: 10.1371/journal.pone.0035056] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 03/08/2012] [Indexed: 11/24/2022] Open
Abstract
The nanoscale protrusions of different morphologies on wing surfaces of four cicada species were examined under an environmental scanning electron microscope (ESEM). The water contact angles (CAs) of the wing surfaces were measured along with droplet adhesion values using a high-sensitivity microelectromechanical balance system. The water CA and adhesive force measurements obtained were found to relate to the nanostructuring differences of the four species. The adhesive forces in combination with the Cassie-Baxter and Wenzel approximations were used to predict wetting states of the insect wing cuticles. The more disordered and inhomogeneous surface of the species Leptopsalta bifuscata demonstrated a Wenzel type wetting state or an intermediate state of spreading and imbibition with a CA of 81.3° and high adhesive force of 149.5 µN. Three other species (Cryptotympana atrata, Meimuna opalifer and Aola bindusara) exhibited nanostructuring of the form of conically shaped protrusions, which were spherically capped. These surfaces presented a range of high adhesional values; however, the CAs were highly hydrophobic (C. atrata and A. bindusara) and in some cases close to superhydrophobic (M. opalifer). The wetting states of A. bindusara, C. atrata and M. opalifer (based on adhesion and CAs) are most likely represented by the transitional region between the Cassie-Baxter and Wenzel approximations to varying degrees.
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Affiliation(s)
- Mingxia Sun
- Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Aiping Liang
- Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Gregory S. Watson
- School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Queensland, Australia
| | - Jolanta A. Watson
- School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Queensland, Australia
| | - Yongmei Zheng
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Beijing, China
| | - Jie Ju
- Center of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Lei Jiang
- Center of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
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Hu HM, Watson JA, Cribb BW, Watson GS. Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants. BIOFOULING 2011; 27:1125-1137. [PMID: 22081886 DOI: 10.1080/08927014.2011.637187] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The adhesional properties of contaminating particles of scales of various lengths were investigated for a wide range of micro- and nanostructured insect wing cuticles. The contaminating particles consisted of artificial hydrophilic (silica) and spherical hydrophobic (C(18)) particles, and natural pollen grains. Insect wing cuticle architectures with an open micro-/nanostructure framework demonstrated topographies for minimising solid-solid and solid-liquid contact areas. Such structuring of the wing membranes allows for a variety of removal mechanisms to contend with particle contact, such as wind and self-cleaning droplet interactions. Cuticles exhibiting high contact angles showed considerably lower particle adhesional forces than more hydrophilic insect surfaces. Values as low as 3 nN were recorded in air for silica of ~28 nm in diameter and <25 nN for silica particles 30 μm in diameter. A similar adhesional trend was also observed for contact with pollen particles.
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Affiliation(s)
- Hsuan-Ming Hu
- School of Pharmacy and Molecular Sciences, James Cook University, Townsville, QLD 4811, Australia
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