There are two major structural paradigms in robotics: soft machines, which are conformable, durable, and safe; and traditional rigid robots, which are fast, precise, and capable of applying high forces. Here, the paradigms are bridged by enabling soft machines to behave like traditional rigid robots on command. This task is accomplished via laminar jamming, a structural phenomenon in which a laminate of compliant strips becomes strongly coupled through friction when a pressure gradient is applied, causing dramatic changes in mechanical properties. Rigorous analytical and finite element models of laminar jamming are developed, and jamming structures are experimentally characterized to show that the models are highly accurate. Then jamming structures are integrated into soft machines to enable them to selectively exhibit the stiffness, damping, and kinematics of traditional rigid robots. The models allow jamming structures to efficiently meet arbitrary performance specifications, and the physical demonstrations illustrate how to construct systems that can behave like either soft machines or traditional rigid robots at will, such as continuum manipulators that can rapidly have joints appear and disappear. This study aims to foster a new generation of mechanically versatile machines and structures that cannot simply be classified as “soft” or “rigid.”

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Soft robots require sensors that are soft, stretchable, and conformable to preserve their adaptivity and safety. In this work, hydrogels are successfully applied as large‐strain sensors for elastomeric structures such as soft robots. Following a simple surface preparation step based on silane chemistry, prefabricated sensors are strongly bonded to elastomers via a “stick‐on” procedure. This method separates the construction of the soft robot's structure and sensors, expanding the potential design space for soft robots that require integrated sensing. The adhesion strength is shown to exceed that of the hydrogel itself, and the sensor is characterized via quasi‐static, fatigue, and dynamic response tests. The sensor exhibits exceptional electrical and mechanical properties: it can sense strains exceeding 400% without damage, maintain stable performance after 1500 loading cycles, and has a working bandwidth of at least 10 Hz, which is sufficient for rapidly‐actuated soft robots. In addition, the hydrogel‐based large‐strain sensor is integrated into a soft pneumatic actuator, and the sensor effectively measures the actuator's configuration while allowing it to freely deform. This work provides “stick‐on” large‐strain sensors for soft robots and will enable novel functionality for wearable robots, potentially serving as a “sensing skin” through stimuli‐responsive hydrogels.

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There is a major need in the developing world for a low-cost prosthetic knee that enables users to walk with able-bodied kinematics and low energy expenditure. To efficiently design such a knee, the relationship between the inertial properties of a prosthetic leg and joint kinetics and energetics must be determined. In this paper, using inverse dynamics, the theoretical effects of varying the inertial properties of an above-knee prosthesis on the prosthetic knee moment, hip power, and absolute hip work required for walking with able-bodied kinematics were quantified. The effects of independently varying mass and moment of inertia of the prosthesis, as well as independently varying the masses of each prosthesis segment, were also compared. Decreasing prosthesis mass to 25% of physiological leg mass increased peak late-stance knee moment by 43% and decreased peak swing knee moment by 76%. In addition, it reduced peak stance hip power by 26%, average swing hip power by 76%, and absolute hip work by 22%. Decreasing upper leg mass to 25% of its physiological value reduced absolute hip work by just 2%, whereas decreasing lower leg and foot mass reduced work by up to 22%, with foot mass having the greater effect. Results are reported in the form of parametric illustrations that can be utilized by researchers, designers, and prosthetists. The methods and outcomes presented have the potential to improve prosthetic knee component selection, facilitate able-bodied kinematics, and reduce energy expenditure for users of low-cost, passive knees in developing countries, as well as for users of advanced active knees in developed countries.