Upmanyu M, Wang H L, Liang H Y, Mahajan R
Group for Simulation and Theory of Atomic-Scale Material Phenomena (stAMP), Division of Engineering, Colorado School of Mines, Golden, CO 80401, USA.
J R Soc Interface. 2008 Mar 6;5(20):303-10. doi: 10.1098/rsif.2007.1145.
Coupling between axial and torsional degrees of freedom often modifies the conformation and expression of natural and synthetic filamentous aggregates. Recent studies on chiral single-walled carbon nanotubes and B-DNA reveal a reversal in the sign of the twist-stretch coupling at large strains. The similarity in the response in these two distinct supramolecular assemblies and at high strains suggests a fundamental, chirality-dependent nonlinear elastic behaviour. Here we seek the link between the microscopic origin of the nonlinearities and the effective twist-stretch coupling using energy-based theoretical frameworks and model simulations. Our analysis reveals a sensitive interplay between the deformation energetics and the sign of the coupling, highlighting robust design principles that determine both the sign and extent of these couplings. These design principles have already been exploited by nature to dynamically engineer such couplings, and have broad implications in mechanically coupled actuation, propulsion and transport in biology and technology.
轴向自由度和扭转自由度之间的耦合常常会改变天然和合成丝状聚集体的构象与表达。最近对手性单壁碳纳米管和B-DNA的研究表明，在大应变下扭转-拉伸耦合的符号会发生反转。这两种不同超分子组装体在高应变下响应的相似性表明了一种基本的、依赖手性的非线性弹性行为。在这里，我们使用基于能量的理论框架和模型模拟来探寻非线性的微观起源与有效扭转-拉伸耦合之间的联系。我们的分析揭示了变形能量学与耦合符号之间的敏感相互作用，突出了决定这些耦合的符号和程度的稳健设计原则。这些设计原则已经被自然界用来动态设计此类耦合，并且在生物学和技术中的机械耦合驱动、推进和运输方面具有广泛的意义。
