Cai Wanhao, Bullerjahn Jakob T, Lallemang Max, Kroy Klaus, Balzer Bizan N, Hugel Thorsten
Institute of Physical Chemistry, University of Freiburg Albertstr. 21 79104 Freiburg Germany
Department of Theoretical Biophysics, Max Planck Institute of Biophysics Max-von-Laue-Straße 3 60438 Frankfurt am Main Germany.
Chem Sci. 2022 Apr 26;13(19):5734-5740. doi: 10.1039/d2sc01077a. eCollection 2022 May 18.
A wealth of chemical bonds and polymers have been studied with single-molecule force spectroscopy, usually by applying a force perpendicular to the anchoring surface. However, the direction-dependence of the bond strength lacks fundamental understanding. Here we establish stereographic force spectroscopy to study the single-bond strength for various pulling angles. Surprisingly, we find that the apparent bond strength increases with increasing pulling angle relative to the anchoring surface normal, indicating a sturdy mechanical anisotropy of a chemical bond. This finding can be rationalized by a fixed pathway for the rupture of the bond, resulting in an effective projection of the applied pulling force onto a nearly fixed rupture direction. Our study is fundamental for the molecular understanding of the role of the direction of force application in molecular adhesion and friction. It is also a prerequisite for the nanoscale tailoring of the anisotropic strength of bottom-up designed materials.
大量的化学键和聚合物已通过单分子力谱进行研究，通常是通过施加垂直于锚定表面的力。然而，键强度的方向依赖性仍缺乏基本认识。在此，我们建立了立体力谱来研究不同拉伸角度下的单键强度。令人惊讶的是，我们发现相对于锚定表面法线，表观键强度随拉伸角度的增加而增加，这表明化学键具有强烈的机械各向异性。这一发现可以通过键断裂的固定路径来解释，从而使施加的拉力有效地投影到几乎固定的断裂方向上。我们的研究对于从分子层面理解力的施加方向在分子粘附和摩擦中的作用至关重要。它也是对自下而上设计材料的各向异性强度进行纳米级定制的先决条件。
