Shape-programmable matter is a class of active materials whose geometry can be controlled to potentially achieve mechanical functionalities beyond those of traditional machines. Among these materials, magnetically actuated matter is particularly promising for achieving complex time-varying shapes at small scale (overall dimensions smaller than 1 cm). However, previous work can only program these materials for limited applications, as they rely solely on human intuition to approximate the required magnetization profile and actuating magnetic fields for their materials. Here, we propose a universal programming methodology that can automatically generate the required magnetization profile and actuating fields for soft matter to achieve new time-varying shapes. The universality of the proposed method can therefore inspire a vast number of miniature soft devices that are critical in robotics, smart engineering surfaces and materials, and biomedical devices. Our proposed method includes theoretical formulations, computational strategies, and fabrication procedures for programming magnetic soft matter. The presented theory and computational method are universal for programming 2D or 3D time-varying shapes, whereas the fabrication technique is generic only for creating planar beams. Based on the proposed programming method, we created a jellyfish-like robot, a spermatozoid-like undulating swimmer, and an artificial cilium that could mimic the complex beating patterns of its biological counterpart.programmable matter | multifunctional materials | soft robots | magnetic actuation | miniature devices S hape-programmable matter refers to active materials that can be controlled by heat (1-5), light (6, 7), chemicals (8-13), pressure (14, 15), electric fields (16, 17), or magnetic fields (18-33) to generate desired folding or bending. As these materials can reshape their geometries to achieve desired time-varying shapes, they have the potential to create mechanical functionalities beyond those of traditional machines (1, 15). The functionalities of shape-programmable materials are especially appealing for miniature devices whose overall dimensions are smaller than 1 cm as these materials could significantly augment their locomotion and manipulation capabilities. The development of highly functional miniature devices is enticing because, despite having only simple rigid-body motions (34-36) and gripping capabilities (37), existing miniature devices have already been used across a wide range of applications pertaining to microfluidics (38, 39), microfactories (40, 41), bioengineering (42, 43), and health care (35, 44).Among shape-programmable matter, the magnetically actuated materials are particularly promising for creating complex timevarying shapes at small scales because their control inputs, in the form of magnetic fields, can be specified not only in magnitude but also in their direction and spatial gradients. Furthermore, as they can be fabricated with a continuum magnetization profile, m, along their bodies, these magne...

Limbless organisms like snakes can navigate nearly all terrain. In particular, desert-dwelling sidewinder rattlesnakes (C. cerastes) operate effectively on inclined granular media (like sand dunes) that induce failure in field-tested limbless robots through slipping and pitching. Our laboratory experiments reveal that as granular incline angle increases, sidewinder rattlesnakes increase the length of their body in contact with the sand. Implementing this strategy in a physical robot model of the snake enables the device to ascend sandy slopes close to the angle of maximum slope stability. Plate drag experiments demonstrate that granular yield stresses decrease with increasing incline angle. Together these three approaches demonstrate how sidewinding 1 arXiv:1410.2945v1 [physics.bio-ph] 11 Oct 2014 with contact-length control mitigates failure on granular media.The majority of terrestrial mobile robots are restricted to laboratory environments, in part because such robots are designed to roll on hard flat surfaces. It is difficult to systematically improve such terrestrial robots because we lack understanding of the physics of interaction with complex natural substrates like sand, dirt and tree bark. We are thus limited in our ability to computationally explore designs for potential all-terrain vehicles; in contrast, many of the recent developments in aerial and aquatic vehicles have been enabled by sophisticated computationaldynamics tools that allow such systems to be designed in silico (1).Compared with human-made devices, organisms such as snakes, lizards, and insects move effectively in nearly all natural environments. In recent years, scientists and engineers have sought to systematically discover biological principles of movement and implement these in robots (2). This "bioinspired robotics" approach (3) has proved fruitful to design laboratory robots with new capabilities (new gaits, morphologies, control schemes) including rapid running (2, 4), slithering (5), flying (6), and swimming in sand (7). Fewer studies have transferred biological principles into robust field-ready devices (4, 8) capable of operating in, and interacting with, natural terrain.Limbless locomotors like snakes are excellent systems to study to advance real-world allterrain mobility. Snakes are masters of most terrains: they can move rapidly on land (9, 10) and through water (11), burrow and swim through sand and soil (12), slither through tiny spaces (13), climb complex surfaces (14), and even glide through the air (15). Relative to legged locomotion, limbless locomotion is less studied, and thus broad principles which govern multi-environment movement are lacking. Recently developed limbless robotic platforms (5), based generally on the snake body plan, are appealing for multi-functional robotics study because they are also capable of a variety of modes of locomotion. These robots can traverse confined spaces, climb trees and pipes, and potentially dive through loose material. However, 2 the gaits that carry these robots across fir...

This review covers recent advancements in the field of bioinspired soft robotics, with a primary focus on the last 4 years (2017)(2018)(2019)(2020). The review serves as a toolbox for an interdisciplinary audience interested in the most recent bioinspired soft robotic technologies. In particular, it highlights and explores the vital components of soft robots, focusing on the enabling mechanisms and their biological inspirations. The first section discusses the materials used to fabricate soft bio inspired robots. Soft bioinspired actuation and sensing are then discussed, exploring their capabilities and implementation by researchers. Existing challenges and future potentials of bioinspired soft robots are addressed in the concluding remarks. This review provides engineers and scientists with the latest technological advancements and information needed for designing and developing the next generation of soft bioinspired robotic systems. The future applications of these robots will be grand and limitless. Materials Used for Bioinspired Sensors and ActuatorsClassical robotic systems are comprised of rigid bodies, actuators, and sensors. Unfortunately, many of these well-developed actuators and sensors are not transferable to soft bodies. Thus, researchers working in soft robotics need to reinvent actuators and sensors for soft moving bodies. Biological organisms can be an excellent inspiration for designing these soft actuators and sensors, allowing for their integration in both soft and rigid bodies. The design process of soft actuators and sensors have to be initiated with material selection and composition, for they are foundations upon which the actuators and sensors will be built around. Presently, a diversified list of materials has been used in the development of soft robotic systems. This section will cover some of the latest advancements in the last 4 years in the area of material selection and composition for the design and development of soft bioinspired actuators and sensors.During the past 4 years, researchers have produced soft bioinspired actuators and sensors using biological material such as muscle tissue, [23,24] and plant fibers; [25] carbon-based materials such as graphite and graphene oxide (GO) [26][27][28][29][30][31] and carbon nanotubes (CN); [32,33] hydrogel materials such as poly(Nisopropylacrylamide) (PNIPAM), [34,35] liquid crystal elastomers (LCE), [36] dielectric elastomers (DE), [37] and ionic polymermetal composites (IPMC). [38] An overview of these materials (Figure 1), along with their underlying mechanisms, are discussed below.Biological systems can perform complex tasks with high compliance levels. This makes them a great source of inspiration for soft robotics. Indeed, the union of these fields has brought about bioinspired soft robotics, with hundreds of publications on novel research each year. This review aims to survey fundamental advances in bioinspired soft actuators and sensors with a focus on the progress between 2017 and 2020, providing a primer for the materials used i...

Narrow crevices are challenging terrain for most organisms and biomimetic robots. Snakes move through crevices using sequential folding and unfolding of their bodies in the manner of an accordion or concertina. In this combined experimental and theoretical investigation, we elucidate this effective means of moving through channels. We measure the frictional properties of corn snakes, their body kinematics and the transverse forces they apply to channels of varying width and inclination. To climb channels inclined at 608, we find snakes use a combination of ingenious friction-enhancing techniques, including digging their ventral scales to double their frictional coefficient and pushing channel walls transversely with up to nine times body weight. Theoretical modelling of a one-dimensional n-linked crawler is used to calculate the transverse force factor of safety: we find snakes push up to four times more than required to prevent sliding backwards, presumably trading metabolic energy for an assurance of wall stability.

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In rectilinear locomotion, snakes propel themselves using unidirectional travelling waves of muscular contraction, in a style similar to earthworms. In this combined experimental and theoretical study, we film rectilinear locomotion of three species of snakes, including red-tailed boa constrictors, Dumeril's boas and Gaboon vipers. The kinematics of a snake's extensioncontraction travelling wave are characterized by wave frequency, amplitude and speed. We find wave frequency increases with increasing body size, an opposite trend than that for legged animals. We predict body speed with 73 -97% accuracy using a mathematical model of a one-dimensional n-linked crawler that uses friction as the dominant propulsive force. We apply our model to show snakes have optimal wave frequencies: higher values increase Froude number causing the snake to slip; smaller values decrease thrust and so body speed. Other choices of kinematic variables, such as wave amplitude, are suboptimal and appear to be limited by anatomical constraints. Our model also shows that local body lifting increases a snake's speed by 31 per cent, demonstrating that rectilinear locomotion benefits from vertical motion similar to walking.

Optimal fiber designs for the maximal pull-off force have been indispensable for increasing the attachment performance of recently introduced gecko-inspired reversible micro/nanofibrillar adhesives. There are several theoretical studies on such optimal designs; however, due to the lack of three-dimensional (3D) fabrication techniques that can fabricate such optimal designs in 3D, there have not been many experimental investigations on this challenge. In this study, we benefitted from recent advances in two-photon lithography techniques to fabricate mushroomlike polyurethane elastomer fibers with different aspect ratios of tip to stalk diameter (β) and tip wedge angles (θ) to investigate the effect of these two parameters on the pull-off force. We found similar trends to those predicted theoretically. We found that β has an impact on the slope of the force-displacement curve while both β and θ play a role in the stress distribution and crack propagation. We found that these effects are coupled and the optimal set of parameters also depends on the fiber material. This is the first experimental verification of such optimal designs proposed for mushroomlike microfibers. This experimental approach could be used to evaluate a wide range of complex microstructured adhesive designs suggested in the literature and optimize them.

Snakes can climb a range of surfaces, from tree trunks to brick walls, using a hitherto poorly understood mechanism. The bellies of snakes are covered in a series of flexible scales that can be activated by the snake to prevent sliding. It is previously shown that conscious snakes can use this ability to double their friction coefficient relative to unconscious snakes. In this combined experimental and theoretical study, we give further evidence that snakes actuate their belly scales. We perform experiments where we slide snakes backwards atop an array of pillars. Our theoretical model suggests snakes that do not apply an opening moment to their scales should have quite short contact with these pillars. In our experiments, snakes slide their ventral scales down the pillars, prolonging contact. Our modeling suggests that this phenomenon can only occur if snakes apply a moment at the scale base. We hope this result encourages further research in actively-generated friction.