*Depth-resolved phase-contrast optical metrology in life sciences and engineering

能够提供弱散射材料体积内三维位移分布的新型相衬光学技术将被开发和应用。最近，PI通过波长扫描、宽带光谱检测或改变照明方向的原理验证实验证明了它们的可行性和前景。这些技术具有一些令人兴奋的特点：它们是全场的，非接触的，由于使用了光学相位信息，位移灵敏度达到10nm数量级，并且可以用于研究静态和动态深度分辨变形场。它们还提供了变形场可以叠加的材料的体积微观结构。然而，这些技术仅限于研究半透明材料，因为它们依赖于从材料内部微观结构反射或反向散射的光。生物组织和透明聚合物是半透明材料的例子，包括皮肤、角膜、视网膜、动脉、环氧树脂和聚酯树脂、光聚合物等。该项目建立在从这些初步实验中吸取的经验教训的基础上，旨在通过开发必要的仪器和数据分析工具来建立和成熟这些技术作为平台技术，并克服已确定的技术限制。这项新技术将研究生命科学和工程中两个重要但迄今为止无法解决的问题：1)脊椎动物角膜的适应性表征，其中在角膜组织内测量的三维位移场将通过使用新的反问题方法（有限元更新和虚拟场方法）来提取角膜内部的材料属性分布；2)颗粒材料的微观力学，其中单个颗粒之间的接触力将通过三维位移场分布来评估。这将有助于量化通过3-D颗粒包传递的载荷，并检查包内力链的假设。

Novel phase contrast optical techniques that can provide 3-D displacement distributions within the volume of weakly scattering materials will be developed and applied. Their feasibility and promise have been recently demonstrated by the PI with proof-of-principle experiments either by using wavelength scanning, broadband spectral detection, or by changing illumination direction. The techniques have some exciting features: they are full-field, non-contact, have a displacement sensitivity of order 10nm due to the use of optical phase information, and can be used to study static and dynamic depth-resolved deformation fields. They also provide the volume microstructure of the material to which the deformation fields can be superimposed. These techniques are, however, limited to study semitransparent materials, as they rely in ligth retroreflected or backscattered from the material internal microstructure. Biological tissues and transparent polymers are examples of semitransparent materials and include skin, cornea, retina, arteries, epoxy and polyester resins, photo-polymers, etc.This project builds upon lessons learned from those preliminary experiments and aims to establish and mature these techniques as a platform technology by developing the necessary instrumentation and data analysis tools and to overcome identified technical limitations. Two important but hitherto insoluble problems in life sciences and engineering will be investigated with this new technology: 1) Compliance characterization of the vertebrate eye cornea, in which 3-D displacement fields measured within the corneal tissue will be used to extract material property distributions inside it by using novel inverse problem approaches (Finite Element Updating and the Virtual Fields Method); and 2) Micromechanics of granular materials, in which contact forces between individual grains will be evaluated from 3-D displacement field distributions. This will serve to quantify the loads transmitted through 3-D granular packs and also to check the hypothesis of force chains within the packs.