Versatile Shape-Morphing of Multistable Structures—A Fluid-Driven Director-Field Design

Shape-morphing structures capable of significantly altering their form and volume play a crucial role in diverse fields, from soft robotics and minimally invasive surgery to deployable structures and environmentally adaptive systems. These materials hold the promise of creating autonomous systems that can adapt to their environment and perform complex tasks without constant human intervention. However, current approaches often face limitations in achieving controllable morphing into various complex shapes while maintaining simplicity in design and actuation.<br/><br/>Our research addresses these challenges by introducing an approach that combines director-field theory with viscous fluid actuation. This method enables the creation of multifunctional, shape-morphing structures capable of controlled transformation into multiple stable, complex 3D surfaces.<br/><br/>The core of our innovation lies in the design of interconnected multistable straw-like deformable tubes, constrained by strategically placed rigid links. This network forms a versatile base structure that can be assembled and connected in numerous configurations. By applying director-field theory, we model and design the links and their assembly process to achieve a diverse range of desired final operational shapes from a single initial structure.<br/><br/>A key feature of our design is the use of viscous fluid actuation, enabling precise control and predictable shape-morphing. This method results in sequential snapping of the bi-stable tube elements, allowing control over the structure’s deployment process. Through carefully sequenced inflation and deflation actuations, all controlled via a single inlet, we can achieve a wide range of stable configurations.<br/><br/>We have successfully demonstrated the ability of our structures to morph from a flat initial shape into multiple complex 3D shapes, including spherical surfaces with positive Gaussian curvature, conical structures with zero Gaussian curvature, and shapes with negative Gaussian curvature. Notably, the final shapes closely match those predicted by director field theory, validating our theoretical framework and showcasing the predictability and reliability of our approach.<br/><br/>The versatility of our method enables potential applications across various fields. In soft robotics, these structures could serve as reconfigurable skeletons or end-effectors that can adapt their shape dynamically to perform delicate tasks. For minimally invasive medical procedures, our technology could improve the design of surgical tools and implants, allowing them to navigate through the body and then morph into patient-specific geometries.<br/><br/>Our work also contributes to the field of programmable matter by demonstrating how materials can be designed to change shape in predictable ways based on fluid input. Furthermore, the shape-morphing capabilities of our structures make them suitable for creating environmentally adaptive surfaces, which could be used in buildings or vehicles to dynamically adjust their shape in response to changing environmental conditions.<br/><br/>In conclusion, this study presents a significant advancement in shape-morphing materials by addressing key limitations in current approaches. By combining director-field theory with viscous fluid actuation, we have created a versatile platform for multistable, controllable, and predictable shape-morphing. This work contributes to the development of autonomous materials and opens new avenues for applications in soft robotics, medical devices, and adaptive structures.