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...

Cephalopods such as octopuses have a combination of a stretchable skin and color-tuning organs to control both posture and color for visual communication and disguise. We present an electroluminescent material that is capable of large uniaxial stretching and surface area changes while actively emitting light. Layers of transparent hydrogel electrodes sandwich a ZnS phosphor-doped dielectric elastomer layer, creating thin rubber sheets that change illuminance and capacitance under deformation. Arrays of individually controllable pixels in thin rubber sheets were fabricated using replica molding and were subjected to stretching, folding, and rolling to demonstrate their use as stretchable displays. These sheets were then integrated into the skin of a soft robot, providing it with dynamic coloration and sensory feedback from external and internal stimuli.

Soft robots actuated by pressurization and inflation of a pneumatic network (a "pneunet") of small channels in elastomeric materials are appealing for their ability to produce sophisticated motions with simple controls. Although current designs of pneu-nets achieve motion with large amplitudes, they do so relatively slowly (that is, over seconds). This paper describes a new design for pneu-nets that reduces the amount of gas that must be transported for inflation of the pneu-net, and thus increases its speed of actuation. A simple actuator can bend from a linear shape to a quasi-circular shape in 50 milliseconds when pressurized at ΔP = 345 kPa. At high rates of pressurization and inflation, the path along which the actuator bends depends on this rate. When inflated fully, the channels and chambers of this new pneu-net design experience only one-tenth the change in volume of that required for a motion of equal amplitude using the previous design. This small change in volume requires comparably low levels of strain in the material at maximum amplitudes of actuation, and commensurately low rates of fatigue and failure. This actuator can operate over a million cycles without significant degradation of performance. This design for soft robotic actuators combines high rates of actuation with high reliability of the actuator, and opens new areas of application for them.

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A pneumatically powered, fully untethered mobile soft robot is described. Composites consisting of silicone elastomer, polyaramid fabric, and hollow glass microspheres were used to fabricate a sufficiently large soft robot to carry the miniature air compressors, battery, valves, and controller needed for autonomous operation. Fabrication techniques were developed to mold a 0.65 meter long soft body with modified Pneu-Net actuators capable of operating at the elevated pressures (up to 138 kPa) required to actuate the legs of the robot and hold payloads of up to 8 kg. The soft robot is safe to handle, and its silicone body is innately resilient to a variety of adverse environmental conditions including snow, puddles of water, direct (albeit limited) exposure to flames, and the crushing force of being run over by an automobile.