Locomotion within granular media: sand swimming skinks

在这个计划中，PI将研究沙漠蜥蜴，沙鱼，如何在颗粒状物质的表面下游泳。将开发成像方法以克服在不透明的陆地介质中可视化生物系统的困难，并将创建计算建模工具以研究生物体与运动方程未知的材料的相互作用。这些努力将发生在三个相互作用的重点领域：（1）生物体运动和动力学测量：将建立一个多平面，高速和分辨率的X射线成像系统，以获得生物体在复杂介质中运动的第一个三维运动学。运动学和力的特征在于通过使用空气流化床系统地改变基质性质。(2)描述颗粒介质对游泳运动的响应的物理实验：开发运动模型将需要了解这种状态下材料响应的物理特性，其中大部分材料的行为像固体，除了生物体周围的一小部分区域表现得像流体。将测量与操纵物体通过颗粒介质相关的力，并将结果用于产生力产生的经验模型。(3)有机体和颗粒介质的计算机模型：由于颗粒介质适合直接数值模拟，因此与实验中使用的致动对象（蜥蜴模型）相互作用的3D分子动力学模拟的开发将导致数字环境相互作用模型，该模型可用于询问颗粒水平的运动以及创建生物有机体在该材料内移动的第一个模型。从研究生物体获得的实验数据将建议将通过物理实验和验证模型发挥的驱动策略。这项研究将开始更深入地了解非牛顿介质中的运动，从而产生一个新的运动生物学模型系统，以及运动模型。这项工作将创建快速建模工具，以帮助设计机器人探索和搜索救援设备，必须通过具有挑战性的地形挖掘。它还将聚集来自不同背景的学生：物理学生将与生物学生互动，以在实验和模型方面取得进展。该计划将作为一个跳板，以开发一门课程，检查运动控制，生物致动器（肌肉）的机械性能，皮肤摩擦，复杂物质的流变学等。在大学之外，该计划将通过让公众参与可见和可理解的科学来提供推广。

In this proposal the PI will study how a desert dwelling lizard, the Sandfish, swims beneath the surface of a granular material. Imaging methods will be developed to surmount the difficulties of visualizing biological systems in opaque terrestrial media and computational modeling tools will be created to study the interaction of the organism with materials whose equations of motion are unknown. These efforts will occur in three interacting thrust areas: (1) Measurements of organism motion and dynamics: A multiplane, high speed and resolution x-ray imaging system will be built to obtain the first three dimensional kinematics of an organism moving within a complex medium. Both the kinematics and forces will be characterized as the substrate properties are systematically varied by use of an air fluidized bed. (2) Physics experiment to characterize response of granular media to swimming motions: Developing models of the locomotion will require understanding the physics of the material response in this regime in which the bulk of the material behaves like a solid except for a small region surrounding the organism which behaves like a fluid. The forces associated with maneuvering objects through the granular medium will be measured and the results use to produce an empirical model of force production. (3) Computer models of organism and granular media: As granular media are amenable to direct numerical simulation, development of a 3D Molecular Dynamics simulation interacting with the actuated objects (lizard models) used in experiment will result in numerical environment interaction models that can be used to interrogate the motion at the grain level as well as to create the first models of biological organisms moving within this material. The experimental data obtained from studying the organism will suggest actuation strategies that will be played through the physics experiments and validated models. This study will initiate the beginnings of a deeper understanding of movement within non-Newtonian media and thus will result in a new model system for locomotion biology, as well as models for locomotion. This work will create rapid modeling tools to aid design of robotic exploration and search & rescue devices that must burrow through challenging terrain. It will also gather students from a diverse range of backgrounds: physics students will interact with biology students to make progress on experiments and models. This program will serve as a springboard to develop a course examining control of locomotion, mechanical properties of biological actuators (muscle), skin friction, rheology of complex matter, etc. Outside the university, the program will provide outreach by engaging the public in visible and graspable science.