Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104.
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104.
Proc Natl Acad Sci U S A. 2018 Jul 10;115(28):7206-7211. doi: 10.1073/pnas.1804702115. Epub 2018 Jun 21.
Programmable shape-shifting materials can take different physical forms to achieve multifunctionality in a dynamic and controllable manner. Although morphing a shape from 2D to 3D via programmed inhomogeneous local deformations has been demonstrated in various ways, the inverse problem-finding how to program a sheet in order for it to take an arbitrary desired 3D shape-is much harder yet critical to realize specific functions. Here, we address this inverse problem in thin liquid crystal elastomer (LCE) sheets, where the shape is preprogrammed by precise and local control of the molecular orientation of the liquid crystal monomers. We show how blueprints for arbitrary surface geometries can be generated using approximate numerical methods and how local extrinsic curvatures can be generated to assist in properly converting these geometries into shapes. Backed by faithfully alignable and rapidly lockable LCE chemistry, we precisely embed our designs in LCE sheets using advanced top-down microfabrication techniques. We thus successfully produce flat sheets that, upon thermal activation, take an arbitrary desired shape, such as a face. The general design principles presented here for creating an arbitrary 3D shape will allow for exploration of unmet needs in flexible electronics, metamaterials, aerospace and medical devices, and more.
可编程的形状变形材料可以采取不同的物理形式，以动态和可控的方式实现多功能性。虽然通过编程不均匀的局部变形将形状从 2D 转变为 3D 已经以各种方式得到了证明，但是逆问题——找到如何对薄片进行编程以使其采用任意所需的 3D 形状——更加困难，但对于实现特定功能至关重要。在这里，我们在薄液晶弹性体（LCE）片材中解决了这个逆问题，其中通过对液晶单体的分子取向进行精确和局部控制来预先编程形状。我们展示了如何使用近似数值方法生成任意表面几何形状的蓝图，以及如何生成局部外在曲率以帮助正确地将这些几何形状转换为形状。在能够忠实地对齐和快速锁定的 LCE 化学的支持下，我们使用先进的自上而下的微制造技术将我们的设计精确地嵌入到 LCE 片材中。因此，我们成功地生产出了扁平薄片，这些薄片在热激活后可以采用任意所需的形状，例如人脸。这里提出的创建任意 3D 形状的一般设计原则将允许探索在柔性电子、超材料、航空航天和医疗设备等领域未满足的需求。
