Developing a molecular blueprint fo mechanical response

为什么松紧带是有弹性的？是什么让绳子变硬了？当我们跑步时，肌腱是如何吸收力量的？这些问题涉及到这些材料的弹性和粘性(“粘弹性”)，即当施加和释放应力时，它们变形多少，然后又恢复到原来的形状。设计特殊机械用途的材料是一个困难的问题，因为有许多不同的因素需要考虑。考虑人造肌腱的必要特性：它必须具有类似于天然肌腱的粘弹性反应，与其在不同负荷条件下(跑步、行走、休息)下的应力-应变特性相匹配；它必须在体温及其周围表现出这些特性；并且它必须具有生物相容性，无论是在其在我们体内的长期稳定性方面，还是在其相对于周围组织的惰性(无毒性)方面。设计一种具有特定的力学、热、化学和时间响应的材料，并在分子水平上理解这种响应是重要的和极其复杂的问题。我们建议通过减少材料中的分子数量来简化问题--我们不是研究肌腱，而是研究它们组成的分子，一次一个。在表征了这些构建块的机械响应后，我们将结合这些构建块来构建更复杂的系统，如肌腱。

Why is an elastic band elastic? What makes a rope stiff? How do our tendons absorb forces when we run? These questions relate to the elasticity and viscosity ("viscoelasticity") of these materials, that is, how much they deform and then return to their original shape when stress is applied and released. To design materials for specific mechanical purposes is a difficult problem, as there are many different factors to take into account. Consider the required properties of an artificial tendon: it must have a viscoelastic response similar to a native tendon, matching its stress-strain characteristics under varying conditions of load (running, walking, resting); it must exhibit these properties at and around body temperature; and it must be biocompatible, both in its long-term stability in our bodies and in its inertness (lack of toxicity) with respect to the surrounding tissues. Designing a material with specified mechanical, thermal, chemical and temporal response, and understanding this response at the molecular level are important and extremely complex problems. We propose to simplify the problem by reducing the number of molecules in the material - instead of examining tendons, we are looking at the molecules they comprise, one at a time. After characterizing the mechanical response of these building blocks, we will then combine these blocks to build more complex systems like a tendon.