Developing a molecular blueprint fo mechanical response

为什么橡皮筋是有弹性的？ 是什么让绳子变硬？ 当我们跑步时，我们的肌腱是如何吸收力量的？ 这些问题与这些材料的弹性和粘性（“粘弹性”）有关，也就是说，当施加和释放应力时，它们会变形多少，然后恢复到原来的形状。 为特定的机械目的设计材料是一个困难的问题，因为有许多不同的因素需要考虑。 考虑人造肌腱所需的特性：它必须具有与天然肌腱相似的粘弹性响应，在不同的载荷条件下匹配其应力-应变特性（跑步、步行、休息）;它必须在体温和体温附近表现出这些特性;而且它必须是生物相容的，既要在我们体内长期稳定，又要对周围组织惰性（无毒性）。 设计一种具有特定机械、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且极其复杂的问题。 我们建议通过减少材料中的分子数量来简化问题-而不是检查肌腱，我们正在研究它们组成的分子，一次一个。 在表征这些积木的机械响应之后，我们将联合收割机结合这些积木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.