Learn about how nature has inspired technological innovations with this book on the similarities between gecko feet and a new adhesive tape. Integrating both historical and scientific perspectives, this book explains how gecko feet inspired the invention of an adhesive. Readers will make connections and examine the relationship between the two concepts. Sidebars, photographs, a glossary, and a concluding chapter on important people in the field add detail and depth to this informational text on biomimicry.
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.
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.
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.
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.
This open access book contains a structured collection of the complete solutions of all essential axisymmetric contact problems. Based on a systematic distinction regarding the type of contact, the regime of friction and the contact geometry, a multitude of technically relevant contact problems from mechanical engineering, the automotive industry and medical engineering are discussed. In addition to contact problems between isotropic elastic and viscoelastic media, contact problems between transversal-isotropic elastic materials and functionally graded materials are addressed, too. The optimization of the latter is a focus of current research especially in the fields of actuator technology and biomechanics. The book takes into account adhesive effects which allow access to contact-mechanical questions about micro- and nano-electromechanical systems. Solutions of the contact problems include both the relationships between the macroscopic force, displacement and contact length, as well as the stress and displacement fields at the surface and, if appropriate, within the half-space medium. Solutions are always obtained with the simplest available method - usually with the method of dimensionality reduction (MDR) or approaches which use the solution of the non-adhesive normal contact problem to solve the respective contact problem.
You are surrounded by stickiness. With every step you take, air molecules cling to you and slow you down; the effect is harder to ignore in water. When you hit the road, whether powered by pedal or engine, you rely on grip to keep you safe. The Post-it note and glue in your desk drawer. The non-stick pan on your stove. The fingerprints linked to your identity. The rumbling of the Earth deep beneath your feet, and the ice that transforms waterways each winter. All of these things are controlled by tiny forces that operate on and between surfaces, with friction playing the leading role. In Sticky, Laurie Winkless explores some of the ways that friction shapes both the manufactured and natural worlds, and describes how our understanding of surface science has given us an ability to manipulate stickiness, down to the level of a single atom. But this apparent success doesn't tell the whole story. Each time humanity has pushed the boundaries of science and engineering, we've discovered that friction still has a few surprises up its sleeve. So do we really understand this force? Can we say with certainty that we know how a gecko climbs, what's behind our sense of touch, or why golf balls, boats and aircraft move as they do? Join Laurie as she seeks out the answers from experts scattered across the globe, uncovering a stack of scientific mysteries along the way.
The comprehensive reference and textbook serves as a timely, practical introduction to the principles of nanotribology and nanomechanics. Assuming some familiarity with macroscopic tribology, 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.
In 1974 when I published my book, Biological Mechanism of Attachment, not many pages were required to report on the attachment devices of insect cuticles. As in most fields of research, our knowledge on this specific subject has simply exploded. Dr. Stanislav N. Gorb now describes the present day level of our knowledge, to which he has personally contributed so much, and a research team working on biological microtribology has gradually developed, also. With modern methods of measurement it is possible to enter the structure – function relationship much more deeply, even down to a molecular level, which was not possible two and a half decades ago. It is a well known fact that, in biology, the more sophisticated the measuring method, the greater the achievement of biological fundamental research, and its resulting evidence. Our knowledge remains at a certain level until new methods once more permit a forward leap. Biological knowledge develops in the form of a stepped curve rather than linear, as reflected in the studies carried out on the attachment devices of insect cuticles.
