CAREER: A Design Methodology for Bio-Inspired Soft Mechanical Systems

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This Faculty Early Career Development (CAREER) Program grant will pioneer a systematic synthesis, analysis and manufacturing framework to realize soft mechanical systems. Soft mechanical systems are static and dynamic structural embodiments that do not contain rigid components made of metals or plastics, conventional actuators such as motors, or interfaces such as joints and couplings. They are instead made up of stretchable skins, tissue-like appendages, fibers and fluids, and are inspired by around 90% of nature's animal species that lack a rigid backbone, such as an octopus arm. The unique feature of these systems is that they are flexible yet strong enough to bear large loads. Unfortunately, these systems have so far not been widely used, because a systematic design framework that can guide their physical realization does currently not exist. This award supports fundamental research that enables such a design framework, in which a soft mechanical system can be synthesized through a systematic combination of simple building blocks with pre-determined attributes. The resulting devices are adaptive, lightweight, energy-efficient and inherently safe for human interaction. They will directly impact the emerging fields of rehabilitation robotics, manufacturing automation, space exploration, and surgery. Furthermore, the award will build on the overarching theme of drawing analogies between nature and engineering to increase creative thinking and enhance problem solving abilities in future engineers, while emphasizing broadening participation of underrepresented groups in research.The key challenge in formulating a generalized design framework for soft mechanical systems involves negotiating the coupled nonlinear interactions among its structural constituents, namely, fluids, stretchable envelopes, and reinforced fibers. The design framework relies on reduced order models to capture these interactions and characterize the kinematic and kinemato-static behavior of a generalized soft mechanical building block. The models can be extended to any structure or mechanism under quasistatic interaction with enclosed fluids. Using these models, a design framework will be developed to synthesize a system, where several building blocks with varying attributes are combined in a series or parallel architecture based on rules and guidelines adapted from traditional machine design, such as constraint matching and geometrically exact kinematics. The design framework will also incorporate optimization methods to refine the system based on novel robustness metrics. Successful realization of the design framework will lead to a reconfigurable stiffness system for use in orthotic braces and a self-knotting active rope for use in surgical suturing and active tethering applications.