Surface Construction and Mechanisms of Adhesion in Tokay Gecko Feet and Characterization of a Bio-inspired Reversible Adhesive Tape PDF Download
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Author: Robert A. Sayer
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Abstract: Several creatures including insects, spiders, and lizards, have developed a unique clinging ability that utilizes dry adhesion. Geckos, in particular, have developed the most complex adhesive structures capable of smart adhesion--the ability to cling on different smooth and rough surfaces and detach at will. These animals make use of on the order of a million microscale hairs (setae) (about 14000/mm2) that branch off into hundreds of nanoscale spatulae. This hierarchical surface construction gives the gecko the adaptability to create a large real area of contact with surfaces. van der Waals forces are the primary mechanism utilized to adhere to surfaces and capillary forces are a secondary effect that can further increase adhesive force. Although a gecko is capable of producing on the order of 20 N of adhesive force, it retains the ability to remove its feet from an attachment surface at will. A man-made fibrillar structure capable of replicating gecko adhesion has the potential for use in dry, superadhesive tapes that would be of use in a wide range of applications. These adhesives could be created using micro/nanofabrication techniques or self-assembly. A fibrillar polyvinylsiloxane (PVS) sample consisting of an array pillars (about 230/mm2) approximately 50 um in diameter, 70 um in height and 60 um center-to-center was compared to an unstructured sample. Structured roughness was found to be more important than random roughness in adhesion. The added roughness of the structured sample increased the hydrophobicity of the surface.
Author: Robert A. Sayer
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Abstract: Several creatures including insects, spiders, and lizards, have developed a unique clinging ability that utilizes dry adhesion. Geckos, in particular, have developed the most complex adhesive structures capable of smart adhesion--the ability to cling on different smooth and rough surfaces and detach at will. These animals make use of on the order of a million microscale hairs (setae) (about 14000/mm2) that branch off into hundreds of nanoscale spatulae. This hierarchical surface construction gives the gecko the adaptability to create a large real area of contact with surfaces. van der Waals forces are the primary mechanism utilized to adhere to surfaces and capillary forces are a secondary effect that can further increase adhesive force. Although a gecko is capable of producing on the order of 20 N of adhesive force, it retains the ability to remove its feet from an attachment surface at will. A man-made fibrillar structure capable of replicating gecko adhesion has the potential for use in dry, superadhesive tapes that would be of use in a wide range of applications. These adhesives could be created using micro/nanofabrication techniques or self-assembly. A fibrillar polyvinylsiloxane (PVS) sample consisting of an array pillars (about 230/mm2) approximately 50 um in diameter, 70 um in height and 60 um center-to-center was compared to an unstructured sample. Structured roughness was found to be more important than random roughness in adhesion. The added roughness of the structured sample increased the hydrophobicity of the surface.
Author: Bharat Bhushan
Publisher: Springer Science & Business Media
ISBN: 3540282483
Category : Technology & Engineering
Languages : en
Pages : 1157
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Book Description
The recent emergence and proliferation of proximal probes, e.g. SPM and AFM, and computational techniques for simulating tip-surface interactions has enabled the systematic investigation of interfacial problems on ever smaller scales, as well as created means for modifying and manipulating nanostructures. In short, they have led to the appearance of the new, interdisciplinary fields of micro/nanotribology and micro/nanomechanics. This volume serves as a timely, practical introduction to the principles of nanotribology and nanomechanics and applications to magnetic storage systems and MEMS/NEMS. Assuming some familiarity with macrotribology/mechanics, the book comprises chapters by internationally recognized experts, who integrate knowledge of the field from the mechanics and materials-science perspectives. They cover key measurement techniques, their applications, and theoretical modelling of interfaces, each beginning their contributions with macro- and progressing to microconcepts. After reviewing the fundamental experimental and theoretical aspects in the first part, Nanotribology and Nanomechanics then treats applications. Three groups of readers are likely to find this text valuable: graduate students, research workers, and practicing engineers. It can serve as the basis for a comprehensive, one- or two-semester course in scanning probe microscopy; applied scanning probe techniques; or nanotribology/nanomechanics/nanotechnology, in departments such as mechanical engineering, materials science, and applied physics. With a Foreword by Physics Nobel Laureate Gerd Binnig Dr. Bharat Bhushan is an Ohio Eminent Scholar and The Howard D. Winbigler Professor in the Department of Mechanical Engineering, Graduate Research Faculty Advisor in the Department of Materials Science and Engineering, and the Director of the Nanotribology Laboratory for Information Storage & MEMS/NEMS (NLIM) at the Ohio State University, Columbus, Ohio. He is an internationally recognized expert of tribology and mechanics on the macro- to nanoscales, and is one of the most prolific authors. He is considered by some a pioneer of the tribology and mechanics of magnetic storage devices and a leading researcher in the fields of nanotribology and nanomechanics using scanning probe microscopy and applications to micro/nanotechnology. He is the recipient of various international fellowships including the Alexander von Humboldt Research Prize for Senior Scientists, Max Planck Foundation Research Award for Outstanding Foreign Scientists, and the Fulbright Senior Scholar Award.
Author: Shihao Hu
Publisher:
ISBN:
Category : Adhesives
Languages : en
Pages : 151
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Book Description
Gecko feet integrate many intriguing functions such as strong adhesion, easy detachment and self-cleaning. Mimicking this biological system leads to the development of a new class of advanced fibrillar adhesives useful in various applications. In spite of many significant progresses that have been achieved in demonstrating the enhanced adhesion strength from divided non-continuous surfaces at micro- and nano- scales, directional dependent adhesion from anisotropic structures, and some tolerance of third body interferences at the contact interfaces, the self-cleaning capability and durability of the artificial fibrillar adhesives are still substantially lagging behind the natural version. These insufficiencies impede the final commercialization of any gecko inspired products. Hence here, we have focused our attentions on these critical issues in both (i) the gecko adhesive systems and (ii) the synthetic counterparts. (i) We tested the self-cleaning of geckos during locomotion and provided the first evidence that geckos clean their feet through a unique dynamic self-cleaning mechanism via digital hyperextension. When walking naturally with hyperextension, geckos shed dirt from their toes twice as fast as they would if walking without hyperextension, returning their feet to nearly 80% of their original stickiness in only 4 steps. Our dynamic model predicts that when setae suddenly release from the attached substrate, they generate enough inertial force to dislodge dirt particles from the attached spatulae. The predicted cleaning force on dirt particles significantly increases when the dynamic effect is included. The extraordinary design of gecko toe pads perfectly combines dynamic self-cleaning with repeated attachment and detachment, making gecko feet sticky yet clean. This work thus provides a new mechanism to be considered for biomimetic design of highly reusable and reliable dry adhesives and devices. (ii) A multiscale modeling approach has been developed to study the force anisotropy, structural deformation and failure mechanisms of a two-level hierarchical CNT structures mimicking the gecko foot hairs. At the nanoscale, fully atomistic molecular dynamics simulation was performed to explore the origin of adhesion enhancement considering the existence of laterally distributed CNT segments. Tube-tube interactions and the collective effect of interfacial adhesion and friction forces were investigated at an upper level. A fraction of the vertically aligned CNT arrays with laterally distributed segments on top was simulated by coarse grained molecular dynamics. The characteristic interfacial adhesive behaviors obtained were further adopted as the cohesive laws incorporated in the finite element models at the device level and fitted with experimental results. The multiscale modeling approach provides a bridge to connect the atomic/molecular configurations and the micro-/nano- structures of the CNT array with its macro-level adhesive behaviors, and the predictions from the modeling and simulation help to understand the interfacial behaviors, processes and mechanics of the gecko inspired fibrillar structures for dry adhesive applications.
Author: Gurpreet Singh (ME)
Publisher:
ISBN:
Category : Adhesion
Languages : en
Pages : 110
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Book Description
The gecko's toes are unique piece of engineering when it comes to attachment and detachment. Artificial structures inspired from geckos mimic the same behaviour but the approach has been to maximise the adhesion between the surfaces whereas the detachment forces haven't been a focus of study. The following thesis deals with the contact mechanics while establishing a relationship between the parameters that affect the contact between the two surfaces. The study has been supported by appropriate numerical analysis of the attachment and detachment mechanics of artificial gecko inspired adhesives. The method adopted for the study process is the finite element analysis which helps observing and concluding the parameters of contact mechanics at nano-scale. It also investigates the contact area between the surfaces produced by artificial adhesives when brought in contact with a rigid surface. The effect of geometries and properties on the contact area and the adhesion between the surfaces has also been studied. The initial parameters and geometry of the model is based on the previous studies conducted on geckos and geckos inspired adhesives. The objective is to determine the parameters and geometries that produce maximum contact area between the surface in contact with least amount of forces to require for attachment and detachment of these artificial surfaces.
Author: Zhilong Peng
Publisher: Springer
ISBN: 3662469553
Category : Technology & Engineering
Languages : en
Pages : 107
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Book Description
The thesis systematically investigates the factors which influence many animals’ robust adhesion abilities and micro-reversible adhesion mechanisms, including the geometric principles of their adhesion, relative humidity, surface roughness and pre-tension. Studies exploring biological adhesion mechanisms are not only of great significance for the design of advanced adhesive materials and adhesion systems for micro-climbing robots, but also very helpful for resolving the problem of adhesion failure in MEMS/NEMS.
Author: Yasong Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 156
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Book Description
Geckos are well known for being rapid climbers that have long existed in nature. The reversible and reusable adhesive on their feet intrigues scientists to explore a bio-mimetic adhesive, which inherits the adhesion properties of the gecko's adhesives. Recent advances in electron microscopy reveal the secret of gecko's climbing ability: there are hierarchical fibrillar structures branching from the skin of their climbing feet. Sizes of these hierarchical fibrils range from micrometer to nanometer. These fibrils are arranged to closely resemble a tree, and these tree like structures form a fibril forest on the skin of the climbing feet. Nano-fibrils in close proximity with the contacting surfaces interact with the substrate through intermolecular forces. Slender micro-fibrils extend the nano-fibrils, which are located at their open ends, to reach recesses of the contacting surfaces. The special arrangement of the fibrillar arrays enables quick attachment and detachment of the feet from surfaces of different materials and varying roughness. Inspired by the gecko's adhesive, artificial fibrillar adhesives have been sought developing for more than a decade. Early attempts were focused on making use of the intermolecular interaction by nano-fibrillar arrays. These artificial fibrillar adhesives have achieved great performance on flat surfaces but not as good when they were used on relatively rough surfaces. Recent attempts of preparing a hierarchical fibrillar structure, which contains fibrils in different length scales, have rare success on improving adhesion performance. Evidence of extra compliancy provided by the hierarchical structure is also not clear. This thesis provides evidence that there is a correlation between structure compliancy and adhesion performance of a hierarchical fibrillar adhesive. Improved compliancy and adhesion forces are observed on a hierarchical fibrillar structure with achievements of several milestones, which include developing methods for preparing and characterizing hierarchical fibrillar structures. Experimental results also reveal the interaction of fibrillar arrays with the contacting surfaces. Information obtained is valuable for future development and application of such artificial fibrillar adhesive.
Author: Sunil Mate
Publisher:
ISBN:
Category : Adhesives
Languages : en
Pages : 36
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Book Description
It is well known that the geckos can cling to almost any surface using highly dense micro/nano fibrils found on the feet that rely on Van Der Waals forces to adhere. A few experimental and theoretical approaches have been taken to understand the adhesion mechanism of gecko feet. This work explains the building procedure of custom experimental setup to test the adhesion force over a temperature range and extends its application in space environment, potentially unsafe working condition. This study demonstrates that these adhesive capable of switching adhesive properties not only at room environment but also over a temperature range of -160 degC to 120 degC in vacuum conditions. These conditions are similar to the condition experienced by a satellite in a space orbiting around the earth. Also, this study demonstrated various detachment and specimen patch preparation methods. The custom-made experimental setup for adhesion test can measure adhesion force in temperature and pressure controlled environment over specimen size of 1 sq. inch. A cryogenic cooling system with liquid nitrogen is used to achieve -160 degC and an electric resistive heating system are used to achieve 120 degC in controlled volume. Thermal electrodes, infrared thermopile detectors are used to record temperature at sample and pressure indicator to record vacuum condition in controlled volume. Reversibility of the switching behaviour of the specimen in controlled environment confirms its application in space and very high or very low-temperature conditions. The experimental setup was developed using SolidWorks as a design tool, Ansys as simulation tool and the data acquisition utilizes LabVIEW available in the market today.
Author: Yongkwan Kim
Publisher:
ISBN:
Category :
Languages : en
Pages : 118
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Book Description
Over the last decade, geckos' remarkable ability to stick to and climb surfaces found in nature has motivated a wide range of scientific interest in engineering gecko-mimetic surface for various adhesive and high friction applications. The high adhesion and friction of its pads have been attributed to a complex array of hairy structures, which maximize surface area for van der Waals interaction between the toes and the counter-surface. While advances in micro- and nanolithography technique have allowed fabrication of increasingly sophisticated gecko mimetic surfaces, it remains a challenge to produce an adhesive as robust as that of the natural gecko pads. In order to rationally design gecko adhesives, understanding the contact behavior of fibrillar interface is critical. The first chapter of the dissertation introduces gecko adhesion and its potential applications, followed by a brief survey of gecko-inspired adhesives. Challenges that limit the performance of the current adhesives are presented. In particular, it is pointed out that almost all testing of gecko adhesives have been on clean, smooth glass, which is ideal for adhesion due to high surface energy and low roughness. Surfaces in application are more difficult to stick to, so the understanding of failure modes in low energy and rough surfaces is important. The second chapter presents a fabrication method for thermoplastic gecko adhesive to be used for a detailed study of fibrillar interfaces. Low-density polyethylene nanofibers are replicated from a silicon nanowire array fabricated by colloidal lithography and metal-catalyzed chemical etching. This process yields a highly ordered array of nanofibers over a large area with control over fiber diameter, length, and number density. The high yield and consistency of the process make it ideal for a systematic study on factors that affect adhesion and friction of gecko adhesives. The following three chapters examine parameters that affect macroscale friction of fibrillar adhesives. Basic geometric factors, namely fiber length and diameter, are optimized on smooth glass for high friction. The test surfaces are then processed to intentionally introduce roughness or lower the surface energy in a systematic and quantifiable manner, so that the failure mechanisms of the adhesive can be investigated in detail. In these studies, observed macroscale friction is related to the nano-scale contact behavior with simple mechanical models to establish criteria to ensure high performance of fibrillar adhesives. Chapter 6 presents various methods to produce more complex fiber structures. The metal-assisted chemical etching of silicon nanowires is studied in detail, where the chemical composition of the etching bath can be varied to produce clumped, tapered, tilted, and curved nanowires, which provide interesting templates for molding and are potentially useful for applications in various silicon nanowire devices. Hierarchical fiber structures are fabricated by a few different methods, as well as composite structures where the fibers are embedded in another material. A way to precisely control tapering of microfibers is demonstrated, and the effect of tapering on macroscale friction is studied in detail. The final chapter summarizes the dissertation and suggests possible future works for both further investigating fibrillar interfaces and improving the current gecko adhesive.
Author: Bharat Bhushan
Publisher: Springer
ISBN: 3319282840
Category : Science
Languages : en
Pages : 607
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Book Description
This revised, updated and expanded new edition presents an overview of biomimetics and biologically inspired structured surfaces. It deals with various examples of biomimetics which include surfaces with roughness-induced superomniphobicity, self-cleaning, antifouling, and controlled adhesion. The focus in the book is on the Lotus Effect, Salvinia Effect, Rose Petal Effect, Oleophobic/philic Surfaces, Shark Skin Effect, and Gecko Adhesion. This new edition also contains new chapters on the butterfly wing effect, bio- and inorganic fouling and structure and Properties of Nacre and structural coloration.
Author: Minoru Taya
Publisher: Cambridge University Press
ISBN: 1107065380
Category : Medical
Languages : en
Pages : 539
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Book Description
From experts in engineering and biology, this is the first book to integrate sensor and actuator technology with bioinspired design.
