Session: 06-07 Adaptive Systems in Robotics and Control

Paper Number: 167889

167889 - A Fluidic-Based Bulla-Inspired Interlocking Metasurface 

Interlocking metasurfaces (ILMs) are architected arrays of mating features that create robust non-permanent mechanical joints by constraining motion and transmitting force between adjoining bodies. ILMs find applications in a variety of fields including aerospace and defense, prosthetics, civil engineering, and micro-robotics. Each ILM design has unique functionalities: insertion/removal trajectories and forces, ability to join dissimilar materials, etc, that can be tuned to achieve desired mechanical behaviors by modifying the unit cell geometry, its tiling/placement on the array, and the constituent base materials. Most ILM designs rely on mechanical interference to create the joint; however, there are other physical principles that can be leveraged. While many biological systems use fluidic and structural principles to create attachment, these principles have not yet been explored in interlocking metasurfaces. In this study, we use a problem-driven bio-inspired design framework to develop a fluidic-based ILM design. Considering some general design requirements for modular tunable joints in robotics, we consider a range of organisms that utilize fluids to create attachments. In particular, we investigate how the principles used by fern sporangia and Lernaeopodidae copepods can be used as sources of inspiration. Furn sporangia leverage dehydration in their cells, i.e., the removal of a fluid, to create a large change in curvature of the morphology to release its spores in a catapult fashion. Copepods are parasites that secrete a spherical-shaped organ, the bulla,  to attach to their host: female copepods insert the bulla into the exterior tissue of fish gills, and as the copepod and its bulla grow, the organ serves to permanently attach to the host. We present a fluidic ILM design composed of expanding spherical bladders unit cells. When filled with air, the bladders create mechanical interference between the mating surfaces, creating a non-permanent joint. The expansion of each bladder is controlled by varying the air pressure inside the structure. In this paper, we detail the fabrication process of the bladders, build a simple model to estimate the mating strength, and validate the model experimentally. The bladders are manufactured out of silicon rubber and the mating surfaces are 3D printed using polyjet additive manufacturing. Several mold designs were created to achieve reliable, uniform expanding bladders. A broad range of behaviors can be achieved by selectively activating individual unit cells across the array.  Different activation patterns effectively change the array tiling and allow for modular control of the load path through the interface. This fluidic ILM design may find applications in modular robotics and medical devices.

Presenting Author: Anusha Karandikar Carnegie Mellon University

Presenting Author Biography: Anusha Karandikar is a first-year Ph.D. student in Mechanical Engineering at Carnegie Mellon University. Her research focuses on utilizing bio-inspired design for interlocking metasurfaces in micro-robotic applications. She has a B.S. in Mechanical Engineering from Franklin W. Olin College of Engineering.