The synthesis of soft matter intelligence with circuit‐driven logic has enabled a new class of robots that perform complex tasks or conform to specialized form factors in unique ways that cannot be realized through conventional designs. Translating this hybrid approach to fluidic systems, the present work addresses the need for sheet‐based circuit materials by leveraging the innate porosity of foam—a soft material—to develop pneumatic components that support digital logic, mixed‐signal control, and analog force sensing in wearables and soft robots. Analytical tools and experimental techniques developed in this work serve to elucidate compressible gas flow through porous sheets, and to inform the design of centimeter‐sized foam resistors with fluidic resistances on the order of 109 Pa s m−3. When embedded inside soft robots and wearables, these resistors facilitate diverse functionalities spanning both sensing and control domains, including digital logic using textile logic gates, digital‐to‐analog signal conversion using ladder networks, and analog sensing of forces up to 40 N via compression‐induced changes in resistance. By combining features of both circuit‐based and materials‐based approaches, foam‐enabled fluidic circuits serve as a useful paradigm for future hybrid robotic architectures that fully embody the sensing and computing capabilities of soft fluidic materials.
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The past decade of soft robotics has delivered impactful and promising contributions to society and has seen exponentially increasing interest from scientists and engineers. This interest has resulted in growth of the number of researchers participating in the field and the quantity of their resulting contributions, stressing the community's ability to comprehend and build upon the literature. In this work, a data‐driven review is presented that addresses the recent surge of research by providing a quantitative snapshot of the field. Relevant data are catalogued with three levels of analysis. First, publication‐level analysis explores high‐level trends in the field and bibliometric relationships across the more detailed analyses. Second, device‐level analysis examines the tethering of robots and the incorporation of component types (actuators, sensors, controllers, power sources) into each robot. Finally, component‐level analysis investigates the compliances, material compositions, and “function media” (energetic methods by which components operate) of each soft robotic component in the analyzed literature. The reported data indicate a significant reliance on elastomeric materials, electrical and fluidic media, and physical tethering; meanwhile, controllers and power sources remain underdeveloped relative to actuators and sensors. These gaps in the surveyed literature are elaborated upon, and promising future directions for the field of soft robotics are identified.
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Abstract This paper describes the fabrication of elastomeric three‐dimensional (3D) structures starting from two‐dimensional (2D) sheets using a combination of direct‐ink printing and relaxation of strain. These structures are fabricated in a two‐step process: first, elastomeric inks are deposited as 2D structures on a stretched elastomeric sheet, and second, after curing of the elastomeric inks, relaxation of strain in the 2D sheet causes it to deform into a 3D shape. To predict bending of elastomeric objects fabricated with this technique, a simple mechanical model is developed. The strategy of using initially 2D materials to fabricate 3D structures offers four new features that complement digital fabrication techniques. (i) It provides a simple route to create shapes with complex curves, suspended features, and internal cavities. (ii) It is a faster method of fabricating some types of shapes than “conventional” 3D printing, because the features are printed in 2D. (iii) It forms surfaces that can be both smoother, and structured in a way that is not compatible with layer‐by‐layer processing. (iv) It forms structures that can be deformed reversibly after fabrication by reapplying strain. This paper demonstrates these features by fabrication of helices, structures inspired by cubes and tables, “pop‐up” structures, and soft grippers.
