Soft robots possess many attributes that are difficult, if not impossible, to achieve with conventional robots composed of rigid materials 1,2. Yet, despite recent advances, soft robots must still be tethered to hard robotic control systems and power sources 3-10. New strategies for creating completely soft robots, including soft analogues of these crucial components, are needed to realize their full potential. Here we report the untethered operation of a robot composed solely of soft materials. The robot is controlled with microfluidic logic 11 that autonomously regulates fluid flow and, hence, catalytic decomposition of an on-board monopropellant fuel supply. Gas generated from the fuel decomposition inflates fluidic networks downstream of the reaction sites, resulting in actuation 12. The body and microfluidic logic of the robot are fabricated using moulding and soft lithography, respectively, and the pneumatic actuator networks, on-board fuel reservoirs and catalytic reaction chambers needed for movement are patterned within the body via a multi-material, embedded 3D printing technique 13,14. The fluidic and elastomeric architectures required for function span several orders of magnitude from the microscale to the macroscale. Our integrated design and rapid fabrication approach enables the programmable assembly of multiple materials within this architecture, laying the foundation for completely soft, autonomous robots. Soft robotics is a nascent field that aims to provide safer, more robust robots that interact with humans and adapt to natural environments better than do their rigid counterparts. Unlike conventional robots composed of rigid materials, soft robots based on hydrogels 15,16 , electroactive polymers 17 , granular media 18 and elastomers 5,19 exhibit elastic moduli ranging from 10 kPa to 1 GPa (ref. 1), are physically resiliant 7,20 and have the ability to passively adapt to their environment 1,2,19. Moulded and laminated elastomers with embedded pneumatic networks are widely used materials in soft robotics 1,21,22. Actuation of these elastomeric composites occurs when interconnected channels that make up the pneumatic network are inflated with incompressible fluids or gases supplied via tethered pressure sources 1. Robotic end effectors with bioinspired 10 and rapid 6 actuation, deployable crawlers 3,7 and swimmers 8 with complex body motions, and robust jumpers 9,23 have been developed on the basis of this design strategy. However, in each case, these robots are either tethered to or carry rigid systems for power and control, yielding hybrid soft-rigid systems 4,7-9. Creating a new class of fully soft, autonomous robots 24 is a grand challenge, because it requires soft analogues of the control and power hardware currently used. Recently, monopropellant fuels have been suggested as a promising fuel source for pneumatically actuated soft robots 4,12. Their rapid decomposition into gas upon exposure to a catalyst offers a strategy for powering soft robotic systems that obviates the need for batteri...

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.

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.

†These authors contributed equally to this work. Abstract:Roboticists have begun to design biologically inspired robots with soft or partially soft bodies, which have the potential to be more robust and adaptable, and safer for human interaction, as compared to traditional rigid robots. However, key challenges in the design and manufacture of soft robots include the complex fabrication processes and the interfacing of soft and rigid components. We employed multi-material 3D printing to manufacture a combustionpowered robot whose body transitions from a rigid core to a soft exterior. This stiffness gradient, spanning three orders of magnitude in modulus, enables reliable interfacing between rigid driving components (controller, battery, etc.) and the primarily soft body, and also enhances performance. Powered by the combustion of butane and oxygen, this robot is able to perform untethered jumping.One Sentence Summary: Interfacing of soft and rigid components through a gradient of material properties increases the robustness of an untethered, jumping soft robot powered by combustion. Main Text:Robots are typically composed of rigid components to promote high precision and controllability. Frequently constructed from hard metals such as aluminum and steel, these robots require large machining equipment and an intricate assembly process. In contrast, recent work has explored the possibility of creating soft-bodied robots (1-5) inspired by invertebrates such as cephalopods (6-8) and insect larvae (9), as well as vertebrates including snakes (10) and fish (11). The use of compliant materials facilitates the development of biologically inspired robotic

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.

Breathing is one of the primary vital signs used to diagnose the health status of patients; it is related to many common disorders and diseases, ranging from pulmonary and cardiovascular diseases to sleep-related disorders. Current methods of monitoring breathing require cumbersome, inconvenient and often expensive devices; this requirement sets practical limitations on the frequency and duration of measurements. This article describes a paper-based moisture sensor that uses the hygroscopic character of paper (i.e. the ability of paper to adsorb water reversibly from the surrounding environment) to measure patterns and rate of respiration by converting the changes in humidity caused by cycles of inhalation and exhalation to electrical signals. The changing levels of humidity that occur in a cycle causes a corresponding change in the ionic conductivity of the sensor, which can be measured electrically. By combining the paper sensor with conventional electronics, data concerning respiration can be transmitted to a nearby smartphone or tablet computer for post-processing, and subsequently stored on a cloud server, or they can be further analysed by a healthcare professional remotely. This means of sensing provides a new and practical solution to the problem of recording and analysing patterns of breathing.3

3D printing is at the crossroads of printer and materials engineering; non-invasive diagnostic imaging; computer aided design (CAD); and structural heart intervention. Cardiovascular applications of this technology development include the use of patient-specific 3D models for medical teaching, exploration of valve and vessel function, surgical and catheter-based procedural planning, and early work in designing and refining the latest innovations in percutaneous structural devices. In this review we discuss the methods and materials being used for 3D printing today. We discuss the basic principles of clinical image segmentation including co-registration of multiple imaging datasets to create an anatomic model of interest. With applications in congenital heart disease, coronary artery disease, and in surgical and catheter-based structural disease – 3D printing is a new tool that is challenging how we image, plan, and carry out cardiovascular interventions.

In vitro 3D culture is an important model for tissues in vivo. Cells in different locations of 3D tissues are physiologically different, because they are exposed to different concentrations of oxygen, nutrients, and signaling molecules, and to other environmental factors (temperature, mechanical stress, etc). The majority of high-throughput assays based on 3D cultures, however, can only detect the average behavior of cells in the whole 3D construct. Isolation of cells from specific regions of 3D cultures is possible, but relies on low-throughput techniques such as tissue sectioning and micromanipulation. Based on a procedure reported previously (“cells-in-gels-in-paper” or CiGiP), this paper describes a simple method for culture of arrays of thin planar sections of tissues, either alone or stacked to create more complex 3D tissue structures. This procedure starts with sheets of paper patterned with hydrophobic regions that form 96 hydrophilic zones. Serial spotting of cells suspended in extracellular matrix (ECM) gel onto the patterned paper creates an array of 200 micron-thick slabs of ECM gel (supported mechanically by cellulose fibers) containing cells. Stacking the sheets with zones aligned on top of one another assembles 96 3D multilayer constructs. De-stacking the layers of the 3D culture, by peeling apart the sheets of paper, “sections” all 96 cultures at once. It is, thus, simple to isolate 200-micron-thick cell-containing slabs from each 3D culture in the 96-zone array. Because the 3D cultures are assembled from multiple layers, the number of cells plated initially in each layer determines the spatial distribution of cells in the stacked 3D cultures. This capability made it possible to compare the growth of 3D tumor models of different spatial composition, and to examine the migration of cells in these structures.