Examples of Implemented Technological Bio-Inspired Surfaces

This chapter examines the multi-scale nature of biological materials. It is shown that this characteristic motivated several design attempts within the field of tribological surfaces. These designs were not easy to implement because of a lack of technological means. Until the push for nanoscale material manipulation, many designs, although conceived and conceptually verified, were not technologically possible. The leap in technologies that matured within the past decade resurrected efforts to manufacture many discarded designs on a commercial scale. The material within this chapter presents samples of existing bio-inspired tribological surfaces. The examples are either a direct replica of the bio-analogue or represent a modification of the surface through a combination of chemical and geometrical changes.

Nature

This chapter discusses the historical origins of the concept of borrowing from nature and coining the science of bio-mimetics. The material also surveys examples of tribological systems in nature. Generation of design in natural systems (geometry, pattern, form, and texture) is shown to be holistic in essence. It synchronizes simple interaction of design constituents and efficient performance. Such an approach yields deterministic design outputs that while conceptually simple are of minimized energy footprint. Natural engineering, it is shown, seeks trans-disciplinary technically viable alternatives to our technological practices. These alternatives, given functional constraints, require minimum effort to construct and economize effort while functioning.

Texturing for Technological Surfaces

This chapter explores methods of engineering the elements of the roughness of a tribological surface and the effect of that process on performance. Texture and topography have a crucial influence on the tribological performance of surfaces. The presentation focuses on the dominant technology of laser texturing. The authors review the principles of the texturing process, its effects on friction and wear, and then discuss existing technical difficulties. It is shown that despite being practiced for a long time, and being promising, laser texturing still lacks standardization. To date, there is no agreement on a standardized design methodology that yields optimized textural features that meet the requirements of a prespecified application.

Filtering Texture From Biological Surfaces to Technological Surfaces

This chapter discusses the impact of absence of a holistic surface-design methodology in the technological realm. The authors show that manifesting designs that merge function, form, and topography to achieve lean performance is currently a bottleneck in the field of tribology. The presented material shows that merging function and topography, while not matured within the realm of manmade surfaces, is advanced in natural designs, especially within the scaled reptiles (Squamata). This prompts many engineers to scour biological analogues for design alternatives. However, the problem of evaluating the viability of a natural surface and judging its suitability for a technological application is frequently encountered. The chapter adresses this problem through a detailed case study that involves extracting metrological information for snakes that engage in rectilinear locomotion.

Fundamentals of Sliding Interaction of Surfaces

This chapter reviews the laws governing the friction behavior of objects. The material starts with a historical view of the evolution of friction laws and how they shaped the science of tribology. The second part of the chapter provides a generalized overview of the mechanics of contact between complying solids. Major contact models are listed, and formulas for calculating area of contact, contact forces, contact stresses are also developed. Finally, the chapter applies the presented information to the contact of biological species. The information presents a summary of the major rules in biological attachments, their adhesion and friction, along with their contact mechanics.

Surfaces and Function

This chapter reviews the origins of surface-system considerations. It highlights the fundamental role a surface plays in preserving the structural integrity of a tribological system and the crucial role of surface texture in maintaining the state of a rubbing material. Here the authors make the case for custom engineering of texture. It is shown that the idea of engineering textural features, while being fundamental, is not easy to implement. They discuss the complexity of the factors involved and how they render the customization process industrially demanding. The main emphasis is on one fundamental factor, namely, the absence of a texture design paradigm that caters to the multi-functionality requirement for futuristic surfaces.

Potential of Bio-Inspiration in 3- and 4-D Printing

This chapter explores the potential of bio-inspiration in 3- and 4-D printing. The authors argue that the true potential of texturing hasn't been realized yet not because of the lack of enabling texturing technologies but because of the severe lack of detailed information about the functional details of texturing in a tribological situation, that is, how surface features, their geometry, interact with the functional gradients present within the subsurface layers to control the friction profile of a structure. The material emphasizes the potential of bio-inspired surfaces in providing a pathway for realizing true synchronization of function through a layer-by-layer customization of surface and subsurface material. In particular the chapter discusses methodologies to extract design parameters that lead to manifesting 4-D printed tribological constructs where surface and sub-surfaces respond optimally to external stimulants represented by the operation conditions of load, speed, and ambient temperature. Successful design of functional deterministic surfaces is not a product of mere biomimicry. Rather, it culminates probing the geometry, texture, form, and construction of the bio-analogue and linking these ingredients to the desired functional profile of the surface in the human engineering domain, that is, generation of bio-inspired functional surface designs stems from implementing design rules rather than replication of natural constructions. Deduction of design rules requires decoding the metrological features and the analysis of surface performance, of bio-analogues using standardized engineering methods. Success in designing a bio-inspired surface, therefore, requires a trans-disciplinary approach that combines engineering, physics, and biology. These don't combine naturally since they entail different methodologies of problem solving and investigations. It is hoped that this book would bridge the gap between the disciplines in the context of biomimetic surface design and construction. Further, it is hoped that the material would equip the reader with the basic skills needed to navigate between the biological and the engineering domains.

Surface Engineering Techniques

This chapter reviews both the economic and technological landscapes of surface engineering. It is shown that surface engineering aims to modify the properties of surface and subsurface layers of an object to meet a specific performance goal. The focus is on the enormous growth in the field in light of emerging technologies that enable manipulation of matter at virtually any scale. The presentation emphasizes the diversity of the subject and its relation to desired performance of objects in tribological situations. The chapter also defines the traits of an ideal tribological surface and briefly discuses obstacles that hinder materialization of the envisioned ideal surface construct.

Classification of Surface Constructs

This chapter discusses routes for the classification of surfaces and the evolution of surface metrology. There are two basic ingredients to the surface of a manufactured workpiece: the manufacturing process and the production technique. Each of the ingredients has an effect on the functionality of a rubbing part. The material provides an answering scheme for a question that often arises about how to characterize the influence of roughness features and how to utilize characterization metrics to predict, then monitor, performance.