This manuscript describes a unique class of locomotive robot: A soft robot, composed exclusively of soft materials (elastomeric polymers), which is inspired by animals (e.g., squid, starfish, worms) that do not have hard internal skeletons. Soft lithography was used to fabricate a pneumatically actuated robot capable of sophisticated locomotion (e.g., fluid movement of limbs and multiple gaits). This robot is quadrupedal; it uses no sensors, only five actuators, and a simple pneumatic valving system that operates at low pressures (<10 psi). A combination of crawling and undulation gaits allowed this robot to navigate a difficult obstacle. This demonstration illustrates an advantage of soft robotics: They are systems in which simple types of actuation produce complex motion.biomimetic | mobile R obotics developed to increase the range of motions and functions open to machines, and to build into them some of the characteristics [including autonomous motion (1-3), adaptability to the environment (4-7), and capability of decision making (8, 9)] of animals, particularly animals with skeletons. Most mobile robots are built with hard materials (hard robots), either by adding treads or wheels (10, 11) to conventional machines to increase their mobility, or by starting with conceptual models based on animals [e.g., Big Dog (12) and many others (13-15)], and replicating some of their features in hard structures. Although robotics has made enormous progress in the last 50 years, hard robots still have many limitations. Some of these limitations are mechanical, and include instability when moving in difficult terrain; some have to do with the ranges of motions afforded by actuators and structures (e.g., metal rods, mechanical joints, and electric motors); some stem from the complexity in control (especially when handling materials and structures that are soft, delicate, and complex in shape). Hard robots fabricated from metals are also often heavy and expensive, and thus are not suitable for some applications.New classes of robots may thus find uses in applications where conventional hard robots are unsuitable. We are interested in a unique class of robots: That is, soft robots fabricated in materials (predominantly elastomeric polymers) that do not use a rigid skeleton to provide mechanical strength. The objective of this work is to demonstrate a soft robot that requires only simple design and control to generate mobility. In this demonstration, we begin to address some of the issues that have limited the development of soft robots. Instead of basing this and other designs on highly evolved animals as models, we are using simpler organisms [e.g., worms (16) and starfish (17)] for inspiration. These organisms, ones without internal skeletons, suggest designs that are simpler to make and are less expensive than conventional hard robots, and that may, in some respects, be more capable of complex motions and functions. Simple, inexpensive systems will probably not replace more complex and expensive ones, but may have different...

The emerging field of soft robotics makes use of many classes of materials including metals, low glass transition temperature (Tg) plastics, and high Tg elastomers. Dependent on the specific design, all of these materials may result in extrinsically soft robots. Organic elastomers, however, have elastic moduli ranging from tens of megapascals down to kilopascals; robots composed of such materials are intrinsically soft À they are always compliant independent of their shape. This class of soft machines has been used to reduce control complexity and manufacturing cost of robots, while enabling sophisticated and novel functionalities often in direct contact with humans. This review focuses on a particular type of intrinsically soft, elastomeric robot À those powered via fluidic pressurization.

Synthetic systems cannot easily mimic the color-changing abilities of animals such as cephalopods. Soft machines, machines fabricated from soft polymers and flexible reinforcing sheets, are rapidly increasing in functionality. This manuscript describes simple microfluidic networks that can change the color, contrast, pattern, apparent shape, luminescence, and surface temperature of soft machines for camouflage and display. The color of these microfluidic networks can be changed simultaneously in the visible and infrared-a capability that organisms do not have. These strategies begin to imitate the functions, although not the anatomies, of color-changing animals.Main Text: Cephalopods (e.g., squid and cuttlefish) have amazing control over their appearance (color, contrast, pattern, and shape) (1, 2). These animals use dynamic body patterns for disguise, for protection, and for warning. Other animals (e.g., chameleons and many insects) can also actively change their coloration for camouflage or display (3, 4). Yet others (e.g., jellyfish and fireflies) use bioluminescence to communicate (5). The color-changing capabilities of these animals have not been replicated using soft synthetic systems, but such systems could enhance the function of certain machines (e.g., robots or prosthetics). This paper describes our initial approaches to change the color, contrast, pattern, apparent shape, luminescence, and infrared (IR) emission (that is, surface temperature) of soft machines 2 fabricated from elastomers and flexible reinforcing sheets (6-8) by changing the color and pattern of microfluidic networks. These systems are first steps toward imitating the functions, although not the anatomies, of cephalopods (9, 10) and other color-changing animals (4). These animals typically change color using specialized cells, such as chromatophores or iridophores (4, 9, 10), not simple microchannels. The near-perfect matching of environments used by colorchanging organisms with highly developed nervous systems is not required for camouflage to be effective.Nature offers countless examples of camouflage and display (3,11, 12). While specific demonstrations of camouflage vary among species, the strategies used have common themes: background matching, disruptive coloration, and disguise (3,11, 12). In background matching,

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Single-crystal nanotubes are commonly observed, but their formation is often not understood. We show that nanotube growth can be driven by axial screw dislocations: Self-perpetuating growth spirals enable anisotropic growth, and the dislocation strain energy overcomes the surface energy required for creating a new inner surface forming hollow tubes spontaneously. This was demonstrated through solution-grown zinc oxide nanotubes and nanowires by controlling supersaturation using a flow reactor and confirmed using microstructural characterization. The agreement between experimental growth kinetics and those predicted from fundamental crystal growth theories confirms that the growth of these nanotubes is driven by dislocations.