Fibrillar Network Adaptive Structure with Ion-transport Actuation

Abstract

The overall objective of this research is to create a new actuation system, emulating the ability of plants to generate large strains while carrying significant structural loads. Specifically, the authors aim to create high-authority active structures by exploring a revolutionary combination of two innovative ideas inspired by the mechanical, chemical, and electrical properties of the plants. The first idea, inspired by the fibrillar network in plant cell walls, is to create a high-mechanical-advantage actuator structure based on flexible matrix composites (FMCs). Through fiber—matrix tailoring of FMC tubes, one can cause the structure to actuate in certain desired directions when pressurized. Second, the actuator concept is combined with a novel electroosmotic (EO) transport mechanism to regulate pressure inside the FMC tube, inspired by the ion-transport and volume-control phenomena in plant cells. By adjusting the applied voltage across a charged porous membrane, one can control the internal pressure and actuator response. The performance of the system (pressure, response time, stroke, load, etc.) can be tuned by proper selection of the membrane (e.g., pore size, surface charge, membrane pore area, etc.) and FMC (materials, fiber angle, etc.) properties. The new system can use natural seawater (ideal for naval applications) or a small amount of onboard solution with appropriate properties for electroosmotic pumping. This approach has several advantages over traditional actuators, such as large stroke/force, design flexibility/scalability, and electrical activation with quiet operation and no moving parts. In this research, the FMC structure and EO pump (EOP) models are developed and validated, and the integrated model is analyzed to provide guidelines for designing the overall actuation system.