A Review of Soft Robots <s> Fundamentals of soft robots <s> Traditional robots have rigid underlying structures that limit their ability to interact with their environment. For example, conventional robot manipulators have rigid links and can manipulate objects using only their specialised end effectors. These robots often encounter difficulties operating in unstructured and highly congested environments. A variety of animals and plants exhibit complex movement with soft structures devoid of rigid components. Muscular hydrostats e.g. octopus arms and elephant trunks are almost entirely composed of muscle and connective tissue and plant cells can change shape when pressurised by osmosis. Researchers have been inspired by biology to design and build soft robots. With a soft structure and redundant degrees of freedom, these robots can be used for delicate tasks in cluttered and/or unstructured environments. This paper discusses the novel capabilities of soft robots, describes examples from nature that provide biological inspiration, surveys the state of the art and outlines existing challenges in soft robot design, modelling, fabrication and control. <s> BIB001 </s> A Review of Soft Robots <s> Fundamentals of soft robots <s> The proliferation of soft robotics research worldwide has brought substantial achievements in terms of principles, models, technologies, techniques, and prototypes of soft robots. Such achievements are reviewed here in terms of the abilities that they provide robots that were not possible before. An analysis of the evolution of this field shows how, after a few pioneering works in the years 2009 to 2012, breakthrough results were obtained by taking seminal technological and scientific challenges related to soft robotics from actuation and sensing to modeling and control. Further progress in soft robotics research has produced achievements that are important in terms of robot abilities—that is, from the viewpoint of what robots can do today thanks to the soft robotics approach. Abilities such as squeezing, stretching, climbing, growing, and morphing would not be possible with an approach based only on rigid links. The challenge ahead for soft robotics is to further develop the abilities for robots to grow, evolve, self-heal, develop, and biodegrade, which are the ways that robots can adapt their morphology to the environment. <s> BIB002
Soft structures made from soft materials and with mobile capabilities abound in nature BIB001 . For instance, muscular hydrostats such as elephant trunks, mammal and lizard tongues as well as octopus arms as shown in Figure 1 are soft structures that can bend, extend and twist [ibid]. These abilities as applied to soft robots are not just different ways to perform usual robot functions; they are rather capabilities for performing actions such as squeezing, stretching, climbing and growing BIB002 . These actions would be impossible using a robot design based on rigid links approach. The integration of soft-matter technologies with morphological computation and embodied paradigms has greatly contributed to an increase in the abilities of soft robots and this is evident in their better performance over traditional robots in real Fundamental understanding of the morphology and functionality of soft structures in nature, however, increases insight and can lead to new design concepts in soft robotics BIB001 . Most of the potential capabilities of soft robots is evident in the natural world [ibid] . Hence, the hydrostatic skeletons and muscular hydrostats would be highlighted. 