Structures or materials that can realize the switching from two-dimensional configurations to complex three-dimensional shapes have broad application prospects in fields such as soft robots, flexible electronics, and flexible tactile interfaces. However, most existing methods preset the shape transformation rules during the manufacturing process, resulting in the inability to refresh the final three-dimensional configuration. To overcome this limitation, researchers are committed to developing reprogrammable three-dimensional structures but face the difficulties of requiring continuous energy input or having limited transformable three-dimensional shapes.
To solve the above problems, Jiang Hanqing's team at the School of Engineering of Westlake University combined mechanical buckling with the jamming mechanism and proposed a new design method for shape-programmable structures. As shown in Figure 1, the shape-programmable structure is composed of layer-jamming variable stiffness units and an elastic substrate. The stiffness of the layer-jamming unit can be regulated by negative pressure. Stretching the elastic substrate will drive the layer-jamming structure to elongate. At this time, inputting vacuum will increase its stiffness. Then, releasing the elastic substrate will induce the layer-jamming structure to buckle, realizing the transformation of the structure from a planar configuration to a three-dimensional configuration. And controlling the initial pre-stretching amount can regulate the protrusion height of the layer-jamming structure, as shown in Video 1.
Figure 1 Shape-programmable structure based on the jamming mechanism and mechanical buckling principle.
Video 1
This strategy can be extended to situations with multiple layer-jamming variable stiffness units, as shown in Figure 2. For linear or circular arrays of layer-jamming units, this work proposes a spatiotemporal buckling driving strategy, which can realize independent control of any layer-jamming variable stiffness unit in the array, providing a new idea for the design of dynamic refreshable three-dimensional metasurfaces.
Figure 2 Dynamic refreshable three-dimensional structure based on the spatiotemporal buckling driving strategy.
To achieve precise customization of three-dimensional metasurfaces, this work proposes a reverse design strategy, as shown in Figure 3. First, pixelate the target surface and extract height information. Then, using the analytical relationship between buckling height and pre-stretching strain, give the corresponding operation matrix to complete the construction of the target surface. In addition, for a specific target configuration, the corresponding origami configuration can be reversely designed to realize the construction of the target three-dimensional structure.
Figure 3 Reverse design strategy.
Figure 4 Demonstration of the refreshability and complex shape deformation ability of large-scale pixelated buckling units.
Video 2
Increasing the number of layer-jamming variable stiffness units in the array is beneficial for the construction of complex three-dimensional metasurfaces. For this reason, this work prepares a metasurface structure composed of 768 units, as shown in Figure 4. In addition, by building a 3D printing platform, efficient preparation of large-scale metasurface structures can be achieved. Based on the above reverse design strategy, the designed metasurface structure can reproduce letters (THINK) or pictures (map, Milky Way), as shown in Video 2. To achieve efficient pneumatic control, this work innovatively proposes a "line scan" pneumatic control strategy, so that using 2N drives can complete the independent control of NN pneumatic units, as shown in Figure 5.
Figure 5 Pneumatic control strategy.
Based on the designed metasurface structure, this work builds a flexible tactile interface for blind education, as shown in Figure 6. Input pictures on the computer side and remotely control the metasurface to present the pictures on the metasurface platform. Visually impaired people can obtain information by touching the three-dimensional metasurface, thus completing information interaction and knowledge acquisition.
Figure 6 Application of dynamic three-dimensional metasurface in blind education.
The first authors of this research work are An Siqi, assistant researcher at Westlake University, Li Xiaowen, postdoctoral fellow, and Guo Zengrong, assistant researcher. The co-authors are Huang Yi, scientific research assistant, and Zhang Yanlin, doctoral student. Jiang Hanqing, chair professor at the School of Engineering of Westlake University, is the corresponding author. This work is supported by the National Natural Science Foundation of China and relevant funds of Westlake University. In addition, special thanks are extended to Vice Chairman Zhao Cheng of the Hangzhou Disabled Persons' Federation for his help and support for this research work!
Source | Jiang Hanqing Laboratory
Written by | An Siqi
Edited by | Peng Yue
Proofread by | Su Lingfei
Paper link:https://www.nature.com/articles/s41467-024-51865-x
