A Two-Color mu-PIV/LIF System to Measure Unsteady Two-Phase Flow and Surfactant Transport Relevant to the Lung

该项目将开发和使用一种实验技术，动态测量微尺度全场速度，界面几何形状和传输过程的尖端附近的半无限气泡通过表面活性剂掺杂的流体闭塞管不稳定地传播。本实验建立的肺气道再开放模型与急性呼吸窘迫综合征（ARDS）相关，ARDS以肺气道塌陷和液体阻塞为特征。随后由机械通气驱动的气道重新开放在气道壁上产生破坏性机械应力，其可导致呼吸机诱导的肺损伤（VILI）。我们假设，伴随着动态表面活性剂运输的非定常流动可能会降低壁应力，因此VILI的发病率。在这项研究中进行的微尺度观测将为我们提供一个显着的了解动态的物理化学相互作用，可以操纵，以减少这种破坏性的刺激的幅度。我们所提出的实验方法的新奇源于使用双色荧光技术，同时耦合微粒子图像测速（PIV）和脉冲激光诱导荧光（PLIV），以非侵入性地测量对流场，界面几何形状和输运过程中的时间依赖性的两相流。我们的技术将允许12.5微米× 12.5微米分辨率的流场的量化？这一非凡的细节将使我们能够第一次确定脉动流中流体相的动态应力场。为此，我们将用<$BODIPY荧光标记Infasurf（ONY，Inc），一种临床上使用的肺表面活性剂替代品。PLIV技术将使我们能够以时间依赖的方式同时跟踪标记的表面活性剂的运输和沉积。这项技术的潜在影响是广泛和重大的。首先，这些能力将使我们能够验证和扩展我们的肺部计算模型，以开发气道重新开放的预测模型。最重要的是，这些结果将使我们能够确定动态表面张力和表面活性剂转运相互作用（包括多层创建和塌陷）之间的关系，可以在机械通气期间利用这些关系来减少可能损害肺的有害机械应力。拟议的研究所提供的技术进步对工程科学很重要，因为它们允许量化迄今为止无法访问的微观现象。此外，该技术具有多学科的影响？除了增强我们对肺气道重新开放的理解之外，这些新的方法学可以容易地应用于获得对单相或多相流中的微流体装置的基本了解，并且因此可以转化为芯片上实验室技术。该项目将为各类学生（本科生、研究生和博士后研究员）提供更多的机会。此外，我们将寻求通过与杜兰大学的LS-LAMP和GAELA项目的关联，从历史上代表性不足的群体中招募研究生。我们将部分支持一名博士后研究员，他将通过指导研究生和本科生来提高他的专业发展。

This project will develop and use an experimental technique to dynamically measure the microscale whole-field velocity, interfacial geometry and transport processes near the tip of a semi-infinite bubble propagating unsteadily through a surfactant-doped fluid-occluded tube. This experimental model of pulmonary airway reopening is relevant to acute respiratory distress syndrome (ARDS), which is characterized by pulmonary airway collapse and fluid occlusion. Subsequent airway reopening, driven by mechanical ventilation, generates damaging mechanical stresses on the airway walls that can result in ventilator-induced lung injury (VILI). We hypothesize that unsteady flows accompanied by dynamic surfactant transport may reduce wall stress and therefore the incidence of VILI. The microscale observations conducted in this study will provide us with a significant understanding of dynamic physicochemical interactions that can be manipulated to reduce the magnitudes of this damaging stimulus. The novelty of our proposed experimental approach stems from the use of a two-color fluorescent technique that simultaneous couples micro-particle image velocimetry (ì-PIV) and pulsed laser induced fluorescence (PLIV) to non-invasively measure convection fields, interfacial geometry and transport processes in time-dependent two-phase flows. Our technique will allow quantification of the flow field with 12.5ìm x 12.5ìm resolution ? this extraordinary detail will allow us to determine, for the first time, the dynamic stress field in the fluid phase in pulsatile flows. To do so, we will fluorescently label Infasurf (ONY, Inc), a pulmonary surfactant replacement used clinically, with â-BODIPY. The PLIV technology will allow us to simultaneously track the transport and deposition of the tagged surfactant in a time-dependent manner. The potential impact for this technology is widespread and significant. First, these capabilities will allow us to validate and expand upon our computational models of the lung in order to develop predictive models of airway reopening. Most importantly, these results will allow us to identify the relationship between the dynamic surface tension and surfactant transport interactions (including multi-layer creation and collapse) that can be exploited during mechanical ventilation to reduce deleterious mechanical stresses that can damage the lung. The technological advances afforded by the proposed research are important to engineering science because they allow for the quantification of micro-scale phenomena that have heretofore been inaccessible. In addition, the techniques have multi-disciplinary implications ? in addition to enhancing our understanding of pulmonary airway reopening, these new methodologies may be readily applied to gain fundamental insight into micro-fluidic devices in single or multi-phase flows, and therefore may find translation to lab-on-chip technologies. This project will provide expanded opportunities to a wide variety of students (undergraduates, graduate students and a post-doctoral researcher). Additionally, we will seek to recruit graduate students from historically underrepresented groups through associations with LS-LAMP and GAELA programs at Tulane University. We will partially support one post-doctoral researcher who will enhance his professional development through the mentoring of graduate students and undergraduate students.