VanSaders Bryan, Glotzer Sharon C
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109.
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109;
Proc Natl Acad Sci U S A. 2021 Jan 19;118(3). doi: 10.1073/pnas.2017377118.
Plastic deformation of crystalline materials with isotropic particle attractions proceeds by the creation and migration of dislocations under the influence of external forces. If dislocations are produced and migrated under the action of local forces, then material shape change can occur without the application of surface forces. We investigate how particles with variable diameters can be embedded in colloidal monolayers to produce dislocations on demand. We find in simulation that when embedded clusters of variable diameter particles are taken through multiple cycles of swelling and shrinking, large cumulative plastic slip is produced by the creation and biased motion of dislocation pairs in the solid for embedded clusters of particular geometries. In this way, dislocations emitted by these clusters (biased "dislocation emitters") can be used to reshape colloidal matter. Our results are also applicable to larger-scale swarms of robotic particles that organize into dense ordered two-dimensional (2D) arrangements. We conclude with a discussion of how dislocations fulfill for colloids the role sought by "metamodules" in lattice robotics research and show how successive applications of shear as a unit operation can produce shape change through slicing and swirling.
具有各向同性粒子吸引力的晶体材料的塑性变形是在外力影响下通过位错的产生和迁移进行的。如果位错是在局部力的作用下产生和迁移的，那么在不施加表面力的情况下材料形状也会发生变化。我们研究了如何将直径可变的粒子嵌入胶体单层中，以便按需产生位错。我们在模拟中发现，当将直径可变的粒子簇进行多次膨胀和收缩循环时，对于特定几何形状的嵌入簇，固体中位错对的产生和有偏运动可导致大量的累积塑性滑移。通过这种方式，这些簇（有偏的“位错发射体”）发射的位错可用于重塑胶体物质。我们的结果也适用于组织成密集有序二维排列的更大规模的机器人粒子群。最后，我们讨论了位错如何在胶体中发挥晶格机器人研究中“元模块”所追求的作用，并展示了作为单元操作的剪切的连续应用如何通过切片和旋转产生形状变化。
