EFRI C3 SoRo: Strong Soft Robots--Multiscale Burrowing and Inverse Design

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This project directly addresses major challenges facing the emerging field of soft robotics. Soft robots are made of inherently compliant materials that are soft, flexible, and move gracefully in three dimensions without requiring discrete joints. However, these highly compliant soft bodies may prove too weak to exert sufficiently large forces to accomplish desired tasks. Additionally, there is a general lack of understanding of how to best navigate the bewildering spectrum of materials, configurations, and designs available to soft robotics. This project explores the properties of 3D-printable polyurethane polymers that can be customized to provide different mechanical properties. This project will create mathematical models of highly deformable structures, and computational tools to solve the "inverse problem" of finding the material parameters and 3D printing pattern that achieve a specified structural behavior. The project will consider two currently infeasible tasks at greatly different length scales. Task 1 is a millimeter-scale patient-specific soft robot catheter for neurovascular and cardiovascular applications, where the robots can gently move through blood vessels without requiring risky surgery, blocking blood flow, or injuring the patient. Task 2 is a meter-scale robot that intelligently burrows underground, with force levels much higher than previously attained by soft robots. Soft robots in the vascular application can inform potential breakthroughs for the treatment of heart disease and stroke. Large burrowing robots could prove beneficial for inspecting underground civil infrastructure or laying new fiber optic cable, irrigation, or power lines. This project is also designed to engage high school students, and inspire them to pursue STEM careers, including future roboticists.This project will establish and validate a mathematical framework for the inverse design of universal soft robots that: 1) provide sophisticated 3-D kinematics by further generalizing fiber-reinforced elastomeric enclosures with beam elements and arbitrary shapes along with exceptional force and power densities that match well-known McKibben actuators; 2) achieve arbitrarily-specified tasks and performance requirements including novel multiscale burrowing behavior; and 3) dictate a new means of robotic, automated manufacturing via 3D printed materials exploiting highly anisotropic elastomers, inextensible fibers, and beam elements and their interfacial chemistries. This mathematical formalism generalizes traditional robot kinematics via a full body mapping incorporating dynamic, arbitrary shape sequences specified by an arbitrary desired task. The coupled innovation in polyurethane chemistry and manufacturing will enable soft robots that exceed the capabilities of existing soft robots and overcome fundamental limitations in their capacity to exert useful force, modulate stiffness, and achieve previously-impossible tasks. This project includes validation experiments on two specific testbeds: (1) millimeter-scale soft robot catheters that locomote through vascular networks, and (2) meter-scale burrowing robots in soils, capable of inferring soil properties to adapt their morphology and motion to suit conditions in naturally occurring, highly heterogeneous, soil deposits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.