正面光聚合实现平面到曲面的可编程形状变形

Programmable Shape-shifting from Planar Sheets to Curved Geometries via Front Photopolymerization Approach

由平面薄片直接变形获得3D形状已经成为一种极具前景的设计方法,其为生物技术、驱动器、传感器和工程中复杂超材料的制造提供了新的手段。目前各类研究平面变形生成三维结构的方法中仍存在诸如加工材料昂贵、工艺控制繁琐和难以独立操作的限制。考虑到正面光聚合过程中光敏树脂的聚合特性,展示一种利用光固化过程中不匹配应力驱动平面到曲面形状变形的设计方法。基于不同光编码模式对聚合物聚合程度的影响及沿光固化厚度方向收缩应力梯度的分布特点,提出复合梁理论并推导准一维梁结构的屈曲变形方程,获得弯曲曲率与曝光剂量间的对应关系,在此基础上,针对准二维平面结构变形具有分叉点和难以控制的难题,建立弹性势能函数计算弯曲平面的能量密度,结合有限元计算分析其变形的几何形态和应力分布规律。最后的物理试验测试结果和花瓣,爪子,二十面体,金字塔等自折叠结构的制造实例验证了方法的有效性。

Transforming planar sheets into desired 3D configurations has emerged as a promising design methodology, which provides new means for the fabrication of the biotechnology, actuators, sensors, and engineering of complex metamaterials. Among various approaches to producing planar-to-3D structures, there are still limitations such as high cost, tedious procedures and non-free-standing operation. Considering the polymerization characteristics of photocurable resin in front photopolymerization process, a design method for transforming planar sheets to 3D configurations using mismatch stress is presented. Based on the influence of discrepant photo patterns on the polymerization degree and the distribution of shrinkage stress gradient along the curing thickness, the composite beam theory is proposed theoretically. Thus, the buckling deformation equations of the quasi-one-dimensional beam are derived to obtain the relation between the bending curvature and the exposure dose. On the basis of this, for the bifurcation and rebelliousness in the quasi-two-dimensional plane structure, the elastic potential energy function is established to calculate the energy density of the bending plane, which combines with finite element calculation to reveal the deformation geometry and stress distribution law. The final mechanical experiments as well as the shape transformation examples of petal, claw, icosahedron, and pyramid verify the feasibility of our approach.