Swirling Propulsion in Complex Fluids and Micro-Swimming Rheometry

微生物的运动往往由于它们所处的流体的复杂性而变得复杂。许多流体（例如，粘液），这些生物体在其中“游泳”含有大的大分子，如限制成功游泳的蛋白质。在这些“粘性”液体中游泳更加困难。最近有理论认为，一种被称为“漩涡”的微生物游动可以在复杂的液体中产生推进力，而这在“简单”、粘性较低的液体中是不可能的。漩涡的特征是物体的一部分绕着轴对称物体的轴线旋转。漩涡是许多微生物游动的一个关键特征。该奖项将开发一种新型的微型机器人，展示复杂流体中涡旋推进的特性，并使用该推进来测量周围流体的特性。因此，它是复杂流体性质的动态传感器或“游泳流变仪”。标准流变仪是一种台式设备，其中流体被带到设备中，并且流体应用的原生环境在设备中再现。复杂流体的剪切流中的应力状态需要测量作为流体中剪切速率的函数的至少三种材料性质。本奖项的目标是通过设计，小型化和优化新开发的“旋转”机器人，流变学将转变为远程，原位传感科学。因此，将“流变仪带到流体应用”，而不是将流体样品带到固定的流变仪。一个网球大小的原型已经创建，并成功地展示了主要概念。机器人的设计，并将继续通过大规模的计算机模拟进行优化。微型机器人将立即在医学和生物学上应用，包括测量滑液的复杂流变学特性，作为对几种疾病状况的直接映射。此外，多个微型机器人将被用于检查这些微型旋流器的集体动力学。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The movement of micro-organisms is often complicated by the complexity of the fluids in which they reside. Many of the fluids (e.g., mucous) in which these organisms “swim” contain large macromolecules such as proteins that limit successful swimming. It is more difficult to swim through these “sticky” fluids. It has recently been suggested theoretically that a type of microbial swimming called “swirl” can create propulsion in complex liquids that would not be possible in “simple,” less sticky fluids. Swirl is characterized by parts of the body spinning around the axis of an axisymmetric body. Swirl is a key feature of the swim stroke of many micro-organisms. This award will develop a novel micro-robot that demonstrates the characteristics of swirl propulsion in complex fluids and uses that propulsion to measure the properties of the surrounding fluid. Thus, it is a dynamic sensor of complex fluid properties or a “swimming rheometer”. Standard rheometers are desktop devices where fluid is brought to the device and the native environment of the fluid application is reproduced in the device. The state of stress in the shear flow of complex fluids requires the measurement of at least three material properties as a function of the shear rate in the fluid. The goal in the present award is that through design, miniaturization, and optimization of a newly developed “swirling” robot, rheometry will be transformed to a remote, in situ sensing science. Thus, one will bring the “rheometer to the fluid application” rather than bringing a fluid sample to a fixed rheometer. A tennis ball-size prototype has already been created and the primary concepts are successfully demonstrated. The robot was designed and will continue to be optimized via large scale computer simulation. The miniaturized robot will have immediate medical and biological applications including measuring the complex rheological properties of synovial fluid as a direct mapping to several disease conditions. Moreover, multiple miniaturized robots will be used to examine the collective dynamics of these micro-swirlers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.