Department of Physics, Indian Institute of Science, Bangalore, Karnataka, 560012, India.
Indian Institute of Technology-Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Nat Commun. 2017 Oct 27;8(1):1160. doi: 10.1038/s41467-017-01441-3.
Buckling and wrinkling instabilities are failure modes of elastic sheets that are avoided in the traditional material design. Recently, a new paradigm has appeared where these instabilities are instead being utilized for high-performance applications. Multiple approaches such as heterogeneous gelation, capillary stresses, and confinement have been used to shape thin macroscopic elastic sheets. However, it remains a challenge to shape two-dimensional self-assembled monolayers at colloidal or molecular length scales. Here, we show the existence of a curvature instability that arises during the crystallization of finite-sized monolayer membranes of chiral colloidal rods. While the bulk of the membrane crystallizes, its edge remains fluid like and exhibits chiral ordering. The resulting internal stresses cause the flat membrane to buckle macroscopically and wrinkle locally. Our results demonstrate an alternate pathway based on intrinsic stresses instead of the usual external ones to assemble non-Euclidean sheets at the colloidal length scale.
屈曲和皱折失稳是弹性薄板的失效模式，在传统的材料设计中会避免出现这种失效模式。最近，出现了一种新的范例，其中这些失稳模式被用于高性能应用。多种方法，如非均匀凝胶化、毛细应力和限制，已被用于塑造宏观弹性薄片。然而，在胶体或分子长度尺度上塑造二维自组装单层仍然是一个挑战。在这里，我们展示了在有限尺寸的手性胶体棒单层膜结晶过程中出现的曲率不稳定性。虽然膜的大部分结晶，但边缘仍然像流体一样，并表现出手性有序。由此产生的内应力导致平膜宏观上弯曲和局部起皱。我们的结果证明了一种基于内在应力的替代途径，而不是通常的外在应力，以在胶体长度尺度上组装非欧几里得薄片。
