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Author: Srinivasan Arul Suresh
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The last 20 years have seen considerable interest in bioinspired dry adhesives, based on discoveries regarding the adhesive system of the gecko and some arthropods. Such adhesives typically have the advantage of being reusable, leaving no residue, and allowing control of the adhesion through loading states. However, the number of practical applications of these adhesives remains small. One possible reason is that unlike in mechanical design, where design, simulation, and testing methodologies are all well established, there are significant gaps in all of these phases of engineering as applied to gecko-inspired adhesives. There are a variety of methods and metrics used for evaluating adhesives, often giving differing results, and even in some cases results that do not accurately reflect those observed in practical applications. Even with an accurate evaluation of an adhesive material, refining the design is challenging, as the design and manufacturing methods are typically time-consuming, highly constraining, or both. At the same time, there continues to be growing interest in the use of these adhesives in wide-ranging applications including reusable tapes and bandages; improved and more gentle industrial grippers; and grasping objects in space, where the combination of large objects, low contact forces, and lack of atmosphere make adhesives of particular interest. To address this growing need for improved ability to design and manufacture adhesives tailored to these applications, a three-pronged approach is taken. An improved method for testing gecko-inspired adhesives is presented. Unlike the common testing paradigms published in the literature, which impose a fixed displacement between the adhesive material and a test surface, the proposed testing method uses a series elastic configuration to apply forces to the adhesive. This shift in test control from displacement-space to force-space allows the testing conditions to be aligned to those seen in applications; whether for climbing, grasping, or adhesive tapes, nearly all applications of gecko-inspired adhesives fundamentally involve force-space constraints in normal conditions. It is shown that by testing the adhesives in similar conditions to those observed in use, the measured limit curves better reflect those seen in practice. Further, in cases where the adhesive structures are more complicated, or more integral to the performance of the adhesive--such as the directional, controllable adhesives at the core of this work--force-space testing enables measuring the full capabilities of the adhesive, which in many cases are impossible to measure in displacement-space. With the ability to accurately measure more complex limit curves, spatial variation is investigated as a means to improve the ability to create adhesives with novel parameters. In this case, the property of interest is a high friction ratio, the ratio of friction in a preferred direction to friction in the opposite direction, a property of the natural gecko adhesive system. Taking inspiration from the spatial variation found on the gecko's feet, an adhesive structure with wedges of varying length is developed, modeled, and analyzed. The friction ratio of this adhesive is measured, indicating an improvement of orders of magnitude over the current state of the art. Further, this adhesive structure also demonstrates the possibility of simplifying the adhesive design problem. Rather than developing a single complex feature to provide all of the desired properties, spatial variation permits the development of multiple features that are individually simpler but interact to provide more complex behavior. A discussion of the manufacturing process and associated fabrication constraints for these designed adhesive geometries follows. The process is an extension of a previous manufacturing process developed for making uniform adhesives. This is coupled with methods for directly incorporating adhesives into larger assemblies to create tightly coupled adhesive and sensing systems. Finally, a simplified design framework is presented, synthesizing many of the concepts from the prior sections. The current state of the art in adhesive simulation and modeling, while useful for understanding and explaining various specific aspects of adhesive design, is not adequate for directly analyzing the adhesion of complex adhesive geometries. The framework is intended to be a heuristic that synthesizes concepts from the various models of adhesion to provide useful guidance for thinking about adhesive designs for particular applications.
Author: Srinivasan Arul Suresh
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
The last 20 years have seen considerable interest in bioinspired dry adhesives, based on discoveries regarding the adhesive system of the gecko and some arthropods. Such adhesives typically have the advantage of being reusable, leaving no residue, and allowing control of the adhesion through loading states. However, the number of practical applications of these adhesives remains small. One possible reason is that unlike in mechanical design, where design, simulation, and testing methodologies are all well established, there are significant gaps in all of these phases of engineering as applied to gecko-inspired adhesives. There are a variety of methods and metrics used for evaluating adhesives, often giving differing results, and even in some cases results that do not accurately reflect those observed in practical applications. Even with an accurate evaluation of an adhesive material, refining the design is challenging, as the design and manufacturing methods are typically time-consuming, highly constraining, or both. At the same time, there continues to be growing interest in the use of these adhesives in wide-ranging applications including reusable tapes and bandages; improved and more gentle industrial grippers; and grasping objects in space, where the combination of large objects, low contact forces, and lack of atmosphere make adhesives of particular interest. To address this growing need for improved ability to design and manufacture adhesives tailored to these applications, a three-pronged approach is taken. An improved method for testing gecko-inspired adhesives is presented. Unlike the common testing paradigms published in the literature, which impose a fixed displacement between the adhesive material and a test surface, the proposed testing method uses a series elastic configuration to apply forces to the adhesive. This shift in test control from displacement-space to force-space allows the testing conditions to be aligned to those seen in applications; whether for climbing, grasping, or adhesive tapes, nearly all applications of gecko-inspired adhesives fundamentally involve force-space constraints in normal conditions. It is shown that by testing the adhesives in similar conditions to those observed in use, the measured limit curves better reflect those seen in practice. Further, in cases where the adhesive structures are more complicated, or more integral to the performance of the adhesive--such as the directional, controllable adhesives at the core of this work--force-space testing enables measuring the full capabilities of the adhesive, which in many cases are impossible to measure in displacement-space. With the ability to accurately measure more complex limit curves, spatial variation is investigated as a means to improve the ability to create adhesives with novel parameters. In this case, the property of interest is a high friction ratio, the ratio of friction in a preferred direction to friction in the opposite direction, a property of the natural gecko adhesive system. Taking inspiration from the spatial variation found on the gecko's feet, an adhesive structure with wedges of varying length is developed, modeled, and analyzed. The friction ratio of this adhesive is measured, indicating an improvement of orders of magnitude over the current state of the art. Further, this adhesive structure also demonstrates the possibility of simplifying the adhesive design problem. Rather than developing a single complex feature to provide all of the desired properties, spatial variation permits the development of multiple features that are individually simpler but interact to provide more complex behavior. A discussion of the manufacturing process and associated fabrication constraints for these designed adhesive geometries follows. The process is an extension of a previous manufacturing process developed for making uniform adhesives. This is coupled with methods for directly incorporating adhesives into larger assemblies to create tightly coupled adhesive and sensing systems. Finally, a simplified design framework is presented, synthesizing many of the concepts from the prior sections. The current state of the art in adhesive simulation and modeling, while useful for understanding and explaining various specific aspects of adhesive design, is not adequate for directly analyzing the adhesion of complex adhesive geometries. The framework is intended to be a heuristic that synthesizes concepts from the various models of adhesion to provide useful guidance for thinking about adhesive designs for particular applications.
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: Sujata K. Bhatia
Publisher: Springer Science & Business Media
ISBN: 1461410800
Category : Technology & Engineering
Languages : en
Pages : 350
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Book Description
Regeneration of tissues and organs remains one of the great challenges of clinical medicine, and physicians are constantly seeking better methods for tissue repair and replacement. Tissue engineering and regenerative medicine have been investigated for virtually every organ system in the human body, and progress is made possible by advances in materials science, polymer chemistry, and molecular biology. This book reviews the current status of biomaterials for regenerative medicine, and highlights advances in both basic science and clinical practice. The latest methods for regulating the biological and chemical composition of biomaterials are described, together with techniques for modulating mechanical properties of engineered constructs. Contributors delineate methods for guiding the host response to implantable materials, and explain the use of biologically-inspired materials for optimal biological functionality and compatibility. The book culminates in a discussion of the clinical applications of regenerative medicine. By integrating engineering and clinical medicine, Engineering Biomaterials for Regenerative Medicine examines how tissue engineering and regenerative medicine can be translated into successful therapies to bridge the gap between laboratory and clinic. The book will aid materials scientists and engineers in identifying research priorities to fulfill clinical needs, and will also enable physicians to understand novel biomaterials that are emerging in the clinic. This integrated approach also gives engineering students a sense of the excitement and relevance of materials science in the development of novel therapeutic strategies.
Author: Anna Rudawska
Publisher: BoD – Books on Demand
ISBN: 9535127837
Category : Science
Languages : en
Pages : 400
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Book Description
This book presents some information regarding adhesives which have applications in industry, medicine and dentistry. The book is divided into two parts: "Adhesives Applications in Medicine and Dentistry" and "Properties of Adhesive." The aim of such a presentation is to present the usage in very different aspects of application of the adhesives and present specific properties of adhesives. Adhesives' advantageous properties and relatively uncomplicated processing methods contribute to their increasing application and their growing popularity in the industry, medicine and other branches. Some adhesives represent properties superior to those of most adhesive materials, due to their excellent adhesion and chemical resistance. A wide variety of adhesives' considerable flexibility in modification of properties of adhesives allows adjusting the composition to particular 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: W.A. Lees
Publisher: Springer Science & Business Media
ISBN: 3662110326
Category : Technology & Engineering
Languages : en
Pages : 155
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Book Description
The possible use of adhesives in a new design should always be considered because of the economic and technical benefits thatthey can confer. Light, stiff and economic structures, free of the blemishes caused by conventional assembly methods, can be fabricated from a variety of materials in combinations which would otherwise be hard to achieve. Similarly, mechanisms may be built up using bonding techniques which are free of the costs and stresses implicit in press fitting. Adhesives are not a panacea, but they do have a great deal to offer as is shown by the vital role they play in modern production engineering. Yet, despite this, they are not generally regarded with enthusiasm by engineers and designers. The reason for this is not hard to find. There are so many adhesives with such diverse properties that, in the absence of a unifying science which can explain not only why adhesives stick but why they behave as they do, a very strong incentive is required to guarantee perseverance. In addition, although the polymeric structures of adhesives are well understood, this knowledge is usually of little help to the engineer who is used to dealing in precise terms and may be readily put off by a subject which he tends to regard as being arcane and wooly.
Author: Emiliano Lepore
Publisher: De Gruyter Open
ISBN: 9788376560816
Category : Adhesion
Languages : en
Pages : 0
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Book Description
The proposed book aims to better understand some of the most challenging and disputed topics that could be found in nature, such as adhesive, anti-adhesive or strong mechanisms in plants or animals. This book offers additional knowledge to scientists, technicians, innovators and others in order to support the technology transfer from scientific research to industrialized products.
Author: Jan-Matthias Braun
Publisher: Frontiers Media SA
ISBN: 288966340X
Category : Science
Languages : en
Pages : 165
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Book Description
Author: Romana Santos
Publisher: Royal Society of Chemistry
ISBN: 1849737134
Category : Technology & Engineering
Languages : en
Pages : 209
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Book Description
Due to their impressive performance biological adhesives have inspired the development of superior industrial adhesives. Biological adhesives often provide elegant solutions to engineering and biomedical requirements and are expected to inspire future technological innovations for adhesives for use in hostile conditions. Containing a selection of papers presented at the 1st International Conference on Biological and Biomimetic Adhesives, this book will showcase the latest advances in the chemical and structural characterisation of adhesives, the mechanical testing of adhesives and theory, fabrication and applications of biomimetic adhesives. Following the work of COST Action TD0909, the aim is to gain greater understanding of the mode of action of biological adhesives to allow successful development of improved synthetic counterparts. Appealing to a wide range of researchers in biology, chemistry, physics and engineering, the title provides the background and drive to improve scientific and technological progress in this important area.
Author: Elliot Wright Hawkes
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The field of gecko-inspired adhesives is a relatively young one. It was born out of the discovery in 2002 of the mechanism of adhesion in the gecko, namely van der Waals forces. It is the microscopic features on the toes of the geckos that are responsible for this adhesion, both the setal stalks and, adorning the setae, the nanoscale spatulae. These features allow adhesion to nearly every surface, rough or smooth, due to their compliance and ability to make intimate contact with the surface. The setae and spatulae are made of beta keratin, which doesn't attract dirt, leading to reusability and even self-cleaning properties. The features only adhere to a surface when loaded in shear, allowing the adhesive to be turned on and off. The time constant of the features is very small, allowing some geckos to take over a dozen steps in a second. Over the past decade, countless research articles have been published describing adhesives that mimic some of the behaviors of gecko adhesive. Most are reusable, some are able to be turned "on" or "off, " others show basic self-cleaning abilities. But all of this research focuses exclusively on mimicking the micro- and nanoscale features of the gecko without considering a question critical to making these technologies useful in the real world: How should gecko adhesives be implemented to efficiently support real-world loads? This is the guiding question of the following work. Because natural gecko adhesives already function well in the real world, there is much to learn with regard to this question from the gecko at a scale slightly larger than that which has been focused upon to date. At the millimeter and centimeter scale, there are lamellae, onto which the seta are affixed, each supported by a number of tendons. Roughly 20 lamellae are on each toe, and 5 toes comprise a foot. The first and fifth toes work in opposition, allowing the gecko to turns its adhesive on by pulling v these toes together, or by pulling two opposing feet together. This work explores these larger features of the gecko's anatomy to help answer the guiding question. In this work, two design principles are developed to efficiently support real-world loads with gecko adhesives. These principles inform the design of an ankle built around a tile loaded by a tendon that is directed at the center of pressure of the adhesive (the tendon-loaded tile concept). The ankle allows robots as large as 4 kg with payload to climb vertical glass walls, and the adhesive on the device is shown to achieve nearly identical performance to a small sample of adhesive tested in a carefully aligned setup. Building upon the design principles and the tendon-loaded tile concept, a family of designs provide solutions to the guiding question for a broad set of real-world loading situations. A single tendon-loaded tile has a maximum adhesive size and therefore load: if it becomes too large it no longer can match the slight non-flatness seen in real- world surfaces. Therefore, to expand the capabilities of the tendon-loaded tile to large areas, a new method of load-sharing among many small tendon-loaded tiles is described. Very little drop off in adhesive performance is shown, even as the adhesive area increases by four orders of magnitude. A device implemented with such load- sharing allows a human to scale a vertical glass surface with a hand-sized area of gecko-inspired adhesive. During climbing, the tendon-loaded tile is lifted from the surface between steps. However, for very small "micro"--Robots this requires mechanical complexity that be- comes difficult to incorporate at a small scale. Therefore, to expand the implemen- tation of adhesives to a small scale, a highly anisotropic version of the adhesive is introduced that creates 200 times more adhesion in one shear direction than the other. A 20 mg climber with two tendon-loaded tiles, each equipped with anisotropic adhe- sive and connected by a single actuator, shows the ability to climb at a scale orders of magnitude smaller than any previous climber. In the above climbing applications, the load is directed mostly along the surface in the tangential direction. In order to support the real-world loading situations where the load is directed perpendicularly from the surface, a pair of tendon-loaded tiles are vi loaded in opposition, inspired by the opposed toes and feet of the gecko. A device with opposed tiles loaded by a common tendon shows the ability to grasp smooth surfaces while requiring almost no pressing force to initiate the grasp and almost no pulling force to release the grasp when desired. This opposed adhesive device is modified for rapid attachment and shown to allow a flying micro air vehicle to perch on a smooth vertical surface. All of the above solutions based on the tendon-loaded tile work on nominally flat surfaces. In order to expand the implementation of adhesives to non-flat surfaces, the rigid section of the tendon-loaded tile is replaced with a thin film cast directly with adhesive. A device is shown grasping a large variety of surface textures and shapes, and a model is presented describing the relationship between surface curvature and maximum adhesion.
