In recent years, there has been considerable interest in developing novel underwater vehicles that use propulsion systems inspired by biology [1,2]. Such vehicles have the potential to uncover new mission capabilities and improve maneuverability, efficiency, and speed [3,4]. Here we will explore the physical mechanisms that govern the performance – especially swimming speed and efficiency – of propulsive techniques inspired by biology. We will also show that we can translate the understanding we have gained from biology to the design of a new generation of underwater vehicles.

Bamboo is a group of perennial grasses in the family Poaceae, subfamily Bambusoideae, tribe Bambuseae [1]. One estimation classified bamboo into 75 genera and approximately 1,500 species [1]. The ordinary species of giant bamboo includes Phyllostachys heterocycla pubescens (Moso), Bambusa stenostachya (Tre Gai), Guadua angustifolia (Guadua), and Dendrocalamus giganteus (Dendrocalamus). Moso is the most widely distributed bamboo for utilization [2]. This species is native to China, and was introduced to Japan in about 1736 and to Europe before 1880 [2]. The word, moso (in Japanese) or mao zhu (in Chinese), means hairy culm sheaths and this bamboo is named for the pubescent down at the bottom of its new culms.

Wetting refers to the interactions between a liquid and a solid in a given environment [1–3]. In particular, it refers to the study of how liquids spread on solids. This field of science involves principles found in fluid mechanics and materials science and is relevant to various natural phenomena and industrial applications.

Size does matter. Whether small or large in body size, all organisms obey the laws of physics and thus are subjected to forces imposed by the physical environment. These forces place constraints on the level of performance in regard to physiology (e.g., metabolic rate, heat transfer), morphological design (e.g., skeletal framework, muscle mechanics), and behavior (e.g., predator–prey interactions, flight, locomotor speed). The structural and functional consequences of a change in size are referred to as scaling [1].

Nature has developed a wide range of materials with specific properties matched to function by combining minerals and organic polymers into hierarchical structures spanning multiple length-scales. For instance, some materials, such as antler, mimic bone structure with a lower mineralization to provide toughness [1,2], whereas many fish scales have graded material properties from the hard, penetration-resistant outer layer to the adaptive lamellae in the collagen fibril subsurface [3,4]. Indeed, biological systems represent an inexhaustible source of inspiration to materials scientists by offering potential solutions for the development of new generations of structural and functional materials [5]. Nature’s key role here is in the complex hierarchical assembly of the structural architectures [6]. The concept of multiscale hierarchical structures, where the microstructure at each level is tailored to local needs, allows the adaptation and optimization of the material form and structure at each level of hierarchy to meet specific functions. Indeed, the complexity and symbiosis of structural biological materials has generated enormous interest of late, primarily because these composite biological systems exhibit mechanical properties that are invariably far superior to those of their individual constituents [7].

Defined as the interface of biology and electronics, “bionics” is the science of integrating electronic devices with biological systems to construct hybrid systems that can restore the full functionality of an impaired biological organ or provide additional features and augmented capabilities (Figure 7.1). Indeed, the main goal of designing bionic organs is to restore the original functionality or replace the anatomical defects with enhanced abilities, such that the resulted hybrid would be able to assist humans in highly complex or hazardous tasks. Despite common artificial organs with merely mechanical and electronic elements, bionic organs consist of both mechanical and cellular components coupled in order to regenerate organ architecture and function, and tissue regrowth [1].

The history of architecture is laced with examples of bioinspiration, ranging from the use of decorative motifs to the implementation of functional and organizational principles found in plant and animal life. Likewise, a unique feature of our planet, one that allows life to flourish, has been named after a building type: The Greenhouse Effect. Exchanges in vocabulary from the fields of biology and construction occur quite frequently, i.e. building skin and cell wall, concrete shell and vault organelle, steel skeleton and body frame, and so on. As relative new sciences, it is no surprise that the fields of biology and earth sciences refer to things of scale and size more commonly understood, i.e. buildings. As they cope with the same environments and abide with the same physics, biology and architecture have developed similar solutions in their efforts to resist gravity’s pull or provide comfort and protection. The development of buildings is one of trial and error, a slow, evolutionary process that has to date produced very different building forms. Life, as well, is quite diverse in form and has arrived at this diversity using a limited palette of building materials and sources of energy. A seminal work on the development of form in biology is a book by D’Arcy W. Thompson, On Growth and Form, which first appeared in 1917 and has since become a landmark for biologist and bioinspired architects alike [1]. Using mathematical reasoning and physics, Thompson sets out to illustrate nature’s approach to derive shape, and illustrates how the forces at play are the same as those at play in the shaping of all matter, including buildings and bridges. An important tenet of his book concerns the importance of scale, how different physical forces work at different length-scales, and how these forces bring about vastly different results. It follows from his work that physics – the knowledge of nature – is essential to the understanding of biology and also forms a foundation for bioinspired design.

The abundance of flying insects in nature may make them seem ordinary to most of us. However, for approximately 350 million years [1], flying insects have been experimenting successfully with various aspects of flight, including aerodynamics [2,3], wing design [4], sensors [5,6], and flight control [7–9]. As a result, they have developed miniaturized flight apparatus and efficient computation architectures for executing aerobatic feats that are not yet emulated in engineering flight (Figure 11.1). This makes flying insects truly extraordinary small-scale aircraft from nature, and their design and working principles have received wide interest in both engineering and biology communities.