Natural Curvature and Soft Shells: Shape Shifting through Mechanical Instabilities

大自然使用内部刺激以各种方式局部和全局地改变薄而软的材料的曲率。自然曲率发生在许多生物和工程结构通过差异膨胀，加热，或增长。它们是：由蛋白质沿着细胞膜诱导，对团藻胚胎的发育至关重要，并在残余应力的复合板和壳中引起。由于自然曲率可以极大地影响薄体的形态并引起机械不稳定性，因此这提供了一种用于创建能够在复杂形状之间生长、变形和过渡的自适应形状变化结构的方法。该奖项支持薄壳内自然曲率引起的不稳定力学的基础研究。利用这些概念的技术应用，可以使自适应超材料，软机器人致动器和结构材料的设计能够编程控制的形状变化。因此，该项目将推进与机械不稳定性相关的科学;并促进国家健康，繁荣和福利。该奖项还支持数字灵感，通信和教育（DICE）计划的进一步发展。通过强调视觉，语言和书面交流，该计划将继续加强下一代学者的科学交流，并通过创建和管理开放的在线力学内容来扩大公众的参与。这项研究将建立对自然和自发弯曲如何使细长结构和软材料变形的基本理解。它的结果将有助于工程师更强大的抗屈曲壳体，并促进能够根据命令在目标形状之间变化的壳体的设计。研究将确定自然曲率如何为壳体提供抗压力屈曲的击起系数。该研究小组将利用通过残余膨胀控制软材料曲率的实验，结合基于大变形、无旋转壳公式的新型计算模型。将开发一个完全非线性的正、逆计算壳体模型，用于分析具有不断变化的自然曲率的壳体，并通过实验进行验证。最后，将建立对局部应用的自然曲率如何使软壳变形的理解，从而实现利用计算建模来通知实验设计的有针对性的变形。这种理解可能会改变关键技术，其中形状变化材料正在被强烈追求的技术插入，如软机器人，可展开结构和仿生设计。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nature uses internal stimuli to locally and globally change the curvature of thin and soft materials in a variety of ways. Natural curvatures occur in many biological and engineered structures through differential swelling, heating, or growth. They are: induced by proteins along a cell membrane, critical to the eversion of a developing Volvox embryo, and incurred in residually stressed composite plates and shells. Since natural curvature can drastically affect the morphology of thin bodies and induce mechanical instabilities, this provides a means for creating adaptive, shape-shifting structures capable of growing, morphing, and transitioning between complex shapes. This award supports fundamental research on the mechanics of instabilities induced by a natural curvature within thin shells. Harnessing these concepts for technological applications may enable the design of adaptive metamaterials, soft robotic actuators, and structural materials capable of programmatically controlled shape-shifting. Thus, this project will advance the science associated with mechanical instability; and advance the national health, prosperity, and welfare. This award also supports the further development of the digital inspiration, communication, and education (DICE) program. By placing an emphasis on visual, verbal, and written communication, this program will continue to enhance both the scientific communication of the next generation of scholars and broaden the participation of the general public through the creation and curation of open, online mechanics content.This research will establish a fundamental understanding of how natural and spontaneous curvatures deform slender structures and soft materials. Its results will help engineer shells that are more robust against buckling, and facilitate the design of shells capable of changing between target shapes on command. The research will establish how natural curvature can provide shells with a knock-up factor against pressure buckling. The research team will utilize experiments that control curvature in soft materials through residual swelling in conjunction with a novel computational model based on a large deformation, rotation-free shell formulation. A fully nonlinear forward and inverse computational shell model to analyze shells with an evolving natural curvature will be developed and validated with experiments. Finally, an understanding of how locally applied natural curvatures deform soft shells will be established, enabling targeted shape-shifting that utilizes the computational modeling to inform the experimental design. This understanding may transform key technologies where shape-shifting materials are being intensely pursued for technological insertion, like soft robotics, deployable structures, and biomimetic design.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.