Industrial Biomimetics

Akihiro Miyauchi, Masatsugu Shimomura, Akihiro Miyauchi, Masatsugu Shimomura

• Publisher: Jenny Stanford Publishing
• Year: 2019
• Print ISBN: 9789814800075
• eBook ISBN: 9780429602757
• Topic: Technology & Engineering
• Subtopic: Biology
• Index: Technology & Engineering

Biomimetics is an innovative paradigm shift based on biodiversity for sustainability. Biodiversity is not only the result of evolutionary adaption but also the optimized solution of an epic combinatorial chemistry for sustainability, because the diversity has been acquired by biological processes and technology, including production processes, operating principles, and control systems, all of which differ from human technology. In the recent decades, biomimetics has gained a great deal of industrial interest because of its unique solutions for engineering problems.

In this book, researchers have contributed cutting-edge results from the viewpoint of two types of industrial applications of biomimetics. The first type starts with engineering tasks to solve an engineering problem using biomimetics, while the other starts with the knowledge of biology and its application to engineering fields. This book discusses both approaches. Edited by Profs. Masatsugu Shimomura and Akihiro Miyauchi, two prominent nanotechnology researchers, this book will appeal to advanced undergraduate- and graduate-level students of biology, chemistry, physics, and engineering and to researchers working in the areas of mechanics, optical devices, glue materials, sensor devices, and SEM observation of living matter.

Chapter 1

3D Modeling of Shark Skin and Prototype Diffuser for Fluid Control

Akihiro Miyauchi

Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyodaku, Tokyo 101-0062, Japan
[email protected]

Sharks are well known for their fluid control ability, so shark skin has been widely researched [1,2,3,4,5,6,7,8]. Detailed 3D structure data can now be obtained due to the progress of advanced measurement methods such as X-ray micro–computed tomography (micro-CT). Computational fluid dynamics (CFD) has also been enhanced by the rapid progress of computational power. In this chapter, shark skin is taken as an example of biomimetic design (BMD) for industrial applications.

1.1 Analysis of Shark Skin

As pointed out by Vincent et al., the ways of building functional structures are different between biology and technology [9]. The surfaces of living matter have evolved into various functional 3D structures that are beyond human approach [6]. One example is the placoid scales (dermal denticles) that cover the surface of shark skin, as shown in Fig. 1.1. As you can see, the denticles have groove structures on each scale. A shark mainly moves about one-third of its body (i.e., its tail) to swim. The tail scales at the tail have deeper grooves than those at the head, so the denticles seem to be structured for fluid control. Therefore, 3D measurement of the denticle shape is needed to reveal the mechanism of fluid control.

Figure 1.1 Scanning electron microscopy (SEM) images of denticles on the silvertip shark.

X-ray micro–computed tomography (micro-CT) is a powerful tool to measure the 3D features at the micron scale. X-ray micro-CT measures a lot of cross sections of a specimen in microscale resolution. The 3D topography of denticles can be obtained by image synthesis. Figure 1.2 shows the four kinds of shark skins and denticles measured by X-ray micro-CT. Single denticles are extracted from shark skin (aggregate of denticles) by image processing. Quantitative analysis of denticle features is made possible by the synthesis of CT images. The denticle sizes and groove shapes differ for each species. Each species has groove structures on the denticle surface, which is why shark skin is referred to as riblet (simple groove structure).

Figure 1.2 Tomography of shark skins and denticles measured by X-ray micro-CT, and 3D CAD of denticles.

1.2 Biomimetic Design of Shark Skin

The conventional models of shark skin are riblet structures that have been reported to reduce drag [1,2,3,4,5,6,7,8]. In this section, shark skin is modeled on the basis of precise morphological analysis by X-ray micro-CT and computational fluid dynamics (CFD).

The data of tomography obtained by X-ray micro-CT contains inner structure information of denticles, but only surface morphology is necessary for 3D fluid simulations. Thus, on the basis of the denticle tomography data, a 3D surface mesh of each denticle is made, as shown in the bottom column of Fig. 1.2. By using this 3D computer-aided design (CAD) data, fluid states near each denticle are analyzed.

Figure 1.3 shows the fluid model for denticle analysis. The eight denticles are located on the bottom of the model. The water flows along the x direction at 1 m/s. The flow states near the denticles are analyzed.

Figure 1.3 Flow analysis model for denticles.

Figure 1.4 shows the flow vectors in an x-z cross section of Galapagos shark denticles. The upstream vectors appear. This flow is caused by the tilted structure of denticles and is called rising flow, Uz. The same result was reported by Luo et al. [8]. The generation of Uz is obvious because the mainstream conflicts at the slope structure. CFD revealed that Uz increases with slope angle but a vortex is generated at the bottom of slope when the slope angle exceeds about 50°. The tilt angles of shark denticles shown in Fig. 1.2 are about 20°–30°. This seems to avoid the energy loss induced by vortex generation during the heaving motion of swimming. Therefore, the slope angle for biomimetic design (BMD) was fixed at 25°.

Figure 1.4 Rising flows by denticles in the x-z cross section (Galapagos shark).

Another feature of the flow state is the longitudinal vortex, wx, as shown in Fig. 1.5. Longitudinal vortexes appear in the y-z plane, and the rotation axis is along the x direction. Both rising flow and longitudinal vortex appear in three species in Fig. 1.2.

Figure 1.5 Longitudinal vortex near the grooves of denticle surface in the y-z cross section (Galapagos shark).

The generation model of the longitudinal vortex is shown in Fig. 1.6. Imagine that the main flow paths are through the denticle groove. The flows contact the groove walls and receive the drag. The drag depends on the contact area, so a small wall surface (S₁) causes less drag than a large wall surface (S₂). The flow velocity v₁ near the surface S₁ becomes faster than v₂. The product of pressure p and velocity v is constant, so the pressure _p1 becomes less than p². This pressure difference in the y-z plane causes the longitudinal vortex. To verify this vortex generation model, the flows near the asymmetric groove structures were investigated.

Figure 1.7a shows the investigated fluid models. The fluid configuration is the rectangular case. The asymmetric grooves were formed on the case bottom. Two types of asymmetric groove structures were investigated: asymmetry in (Fig. 1.7b) groove heights and (Fig. 1.7c) groove widths. Both types have different side wall areas: S₁ and S₂ shown in Fig. 1.6.

Figure 1.6 Generation model of a longitudinal vortex.

Figure 1.7 Investigated model of an asymmetric groove. (a) Fluid...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Chapter 1 3D Modeling of Shark Skin and Prototype Diffuser for Fluid Control
• Chapter 2 Friction Control Surfaces in Nature: Analysis of Firebrat Scales
• Chapter 3 Biomechanics and Biomimetics in Flying and Swimming
• Chapter 4 Shape-Tunable Wrinkles Can Switch Frictional Properties
• Chapter 5 Self-Lubricating Gels: SLUGs
• Chapter 6 Bioinspired Materials for Thermal Management Applications
• Chapter 7 Strange Wing Folding in a Rove Beetle
• Chapter 8 Biotemplating Process for Electromagnetic Materials
• Chapter 9 Application of Structural Color
• Chapter 10 Moth Eye–Type Antireflection Films
• Chapter 11 Transparent Superhydrophobic Film Created through Biomimetics of Lotus Leaf and Moth Eye Structures
• Chapter 12 Adhesion under Wet Conditions Inspired by Marine Sessile Organisms
• Chapter 13 Functional Analysis of the Mechanical Design of the Cricket’s Wind Receptor Hair
• Chapter 14 Echolocation of Bats and Dolphins and Its Application
• Chapter 15 The “NanoSuit®” Preserves Wet/Living Organisms for Observation in High Resolution under a Scanning Electron Microscope
• Index