| NSF Org: |
EFMA Office of Emerging Frontiers in Research and Innovation (EFRI) |
| Recipient: |
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| Initial Amendment Date: | September 5, 2018 |
| Latest Amendment Date: | September 5, 2018 |
| Award Number: | 1830950 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Jordan Berg
jberg@nsf.gov (703)292-5365 EFMA Office of Emerging Frontiers in Research and Innovation (EFRI) ENG Directorate for Engineering |
| Start Date: | September 15, 2018 |
| End Date: | December 31, 2023 (Estimated) |
| Total Intended Award Amount: | $1,977,501.00 |
| Total Awarded Amount to Date: | $1,977,501.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
2221 UNIVERSITY AVE SE STE 100 MINNEAPOLIS MN US 55414-3074 (612)624-5599 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Mechanical Engineering, 111 Chur Minneapolis MN US 55455-0150 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
Special Initiatives, EFRI Research Projects |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
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.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Soft robots promise to more safely and dexterously interact with challenging environments. What can we reasonably expect soft robots to accomplish as they scale down to small sizes (around 3mm diameter) and gentle forces or up to large sizes pressures (centimeters diameter, kilo-Newton forces, and mega-Pascal pressures)? This project sought to explore the capabilities and limits of such robots across multiple scales. We consider situations where soft robots move through tube-like environments, burrow into solids like earthen clay, or interact with human limbs.
Small Scale Regime:
High aspect ratio structures like long, slender soft catheters are used to safely reach through blood vessels into locations critical to medical treatments; e.g. vessel blockages in the brain, heart, or legs.
This research provided a method to infer the internal stiffness of soft slender structures like catheters from how they freely fold under gravity and determined what limits to what typical forces they can exert when in constrained environments (e.g. inside tube-like geometries) as diameters decrease near the 3mm diameter regime. Both are informative for soft catheter designers, including those using fiber-reinforced elastomeric enclosure (FREE) approaches. This work also helped identify fundamental limits to performance as catheter diameters decrease yet still need to exert useful force levels (e.g. pushing against a soft structure) given existing approaches to design and build soft robots. These include static and dynamic buckling when exerting force at the tip, capstan-like limits when wrapping around structures or weaving through tunnels with many turns but needing to pull the slender body behind the advancing tip, and limits to getting energy and actuation at the tip as the aspect ratio increases. Yet some difficult-to-treat medical conditions require soft catheters to exceed these practical limits. We found that biological mechanisms succeeded in this area where traditional soft robotic approaches failed due to limits imposed by physics and practical materials. Specifically, by using liquid-mediated transport of materials to a tip that selectively turns liquid materials to a solid at a growing tip, forming aa growing polymer tube. Innovation in materials helped physically realize and study such novel synthetic growth at the tip of a slender tube. These findings also overcome related issues at larger scales.
Large scale, high force regime:
Fluid power proved particularly effective in larger scale soft robots at higher forces and pressures. FREE structures were explored at this regime to provide an inchworm-like gate for pulling such bodies and fundamental and experimental modeling of clay provided a systematic means to help design and evaluate burrowing head designs for improved performance in such regimes. This allowed long, slender soft robots to burrow into solid substrates like earthen clay which demand high penetration forces. Such work helps inform design of novel subterranean infrastructure creation methods with applications including laying new underground pipes or electrical conduit. The larger size and higher force regime was also explored to create novel medical devices for unmet patient needs. Specifically, novel soft actuators were analyzed, developed, and tested to assist nursing staff in preventing heel ulcers among bedridden patients in intensive care unit settings. Overall the project combined civil engineering, mechanical engineering, materials science, and chemical engineering disciplines to make advances these individual fields would not achieve alone.
Last Modified: 06/11/2024
Modified by: Timothy M Kowalewski
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