Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, Missouri, USA.
Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, Missouri, USA.
J Mech Behav Biomed Mater. 2023 Feb;138:105652. doi: 10.1016/j.jmbbm.2023.105652. Epub 2023 Jan 2.
The goal of this study was to design, fabricate, and characterize hydrogel lattice structures with consistent, controllable, anisotropic mechanical properties. Lattices, based on three unit-cell types (cubic, diamond, and vintile), were printed using stereolithography (SLA) of polyethylene glycol diacrylate (PEGDA). To create structural anisotropy in the lattices, unit cell design files were scaled by a factor of two in one direction in each layer and then printed. The mechanical properties of the scaled lattices were measured in shear and compression and compared to those of the unscaled lattices. Two apparent shear moduli of each lattice were measured by dynamic shear tests in two planes: (1) parallel and (2) perpendicular to the scaling direction, or cell symmetry axis. Three apparent Young's moduli of each lattice were measured by compression in three different directions: (1) the "build" direction or direction of added layers, (2) the scaling direction, and (3) the unscaled direction perpendicular to both scaling and build directions. For shear deformation in unscaled lattices, the apparent shear moduli were similar in the two perpendicular directions. In contrast, scaled lattices exhibit clear differences in apparent shear moduli. In compression of unscaled lattices, apparent Young's moduli were independent of direction in cubic and vintile lattices; in diamond lattices Young's moduli differed in the build direction, but were similar in the other two directions. Scaled lattices in compression exhibited additional differences in apparent Young's moduli in the scaled and unscaled directions. Notably, the effects of scaling on apparent modulus differed between each lattice type (cubic, diamond, or vintile) and deformation mode (shear or compression). Scaling of 3D-printed, hydrogel lattices may be harnessed to create tunable, structures of desired shape, stiffness, and mechanical anisotropy, in both shear and compression.
本研究旨在设计、制作和表征具有一致、可控、各向异性机械性能的水凝胶晶格结构。晶格基于三种单元类型（立方、菱形和菱形十二面体），通过聚乙二醇二丙烯酸酯（PEGDA）的立体光刻（SLA）打印而成。为了在晶格中产生结构各向异性，在每个层中将单元设计文件沿一个方向放大两倍，然后进行打印。通过在两个平面（1）平行和（2）垂直于缩放方向或单元对称轴上进行动态剪切测试，测量了缩放晶格的机械性能，并将其与未缩放晶格进行了比较。通过在三个不同方向上进行压缩测试，测量了每个晶格的三个表观杨氏模量：（1）“构建”方向或添加层的方向，（2）缩放方向，以及（3）垂直于缩放和构建方向的未缩放方向。对于未缩放晶格的剪切变形，两个垂直方向上的表观剪切模量相似。相比之下，缩放晶格在表观剪切模量上表现出明显的差异。在未缩放晶格的压缩中，立方和菱形晶格的表观杨氏模量在各个方向上均不依赖于方向；在菱形晶格中，杨氏模量在构建方向上有所不同，但在其他两个方向上相似。压缩时的缩放晶格在缩放和未缩放方向上表现出表观杨氏模量的额外差异。值得注意的是，缩放对各向异性的影响在每种晶格类型（立方、菱形或菱形十二面体）和变形模式（剪切或压缩）之间存在差异。3D 打印水凝胶晶格的缩放可用于创建具有所需形状、刚度和机械各向异性的可调谐结构，无论是在剪切还是压缩中。
