Center for Biomedical Engineering, Department of Mechanical Engineering, University of Delaware, 126 Spencer Laboratory, Newark, DE 19716, USA.
J Biomech. 2010 May 28;43(8):1598-602. doi: 10.1016/j.jbiomech.2009.12.028. Epub 2010 Feb 24.
Fluid shear stress (FSS) is an important stimulus for cell functions. Compared with the well established parallel-plate and cone-and-plate systems, a rocking "see-saw" system offers some advantages such as easy operation, low cost, and high throughput. However, the FSS spatiotemporal pattern in the system has not been quantified. In the present study, we developed a lubrication-based model to analyze the FSS distributions in a rocking rectangular culture dish. We identified an important parameter (the critical flip angle) that dictates the overall FSS behaviors and suggested the right conditions to achieving temporally oscillating and spatially relatively uniform FSS. If the maximal rocking angle is kept smaller than the critical flip angle, which is defined as the angle when the fluid free surface intersects the outer edge of the dish bottom, the dish bottom remains covered with a thin layer of culture medium. The spatial variations of the peak FSS within the central 84% and 50% dish bottom are limited to 41% and 17%, respectively. The magnitude of FSS was found to be proportional to the fluid viscosity and the maximal rocking angle, and inversely proportional to the square of the fluid depth-to-length ratio and the rocking period. For a commercial rectangular dish (length of 37.6mm) filled with approximately 2 mL culture medium, the FSS at the center of the dish bottom is expected to be on the order of 0.9 dyn/cm(2) when the dish is rocked +5 degrees at 1 cycle/s. Our analysis suggests that a rocking "see-saw" system, if controlled well, can be used as an alternative method to provide low-magnitude, dynamic FSS to cultured cells.
流体切应力（FSS）是细胞功能的重要刺激因素。与成熟的平行板和锥板系统相比，摇臂式“跷跷板”系统具有操作简单、成本低、高通量等优点。然而，该系统中的 FSS 时空模式尚未量化。在本研究中，我们开发了一种基于润滑的模型来分析摇臂矩形培养皿中的 FSS 分布。我们确定了一个重要参数（临界翻转角），该参数决定了整体 FSS 行为，并提出了实现时间振荡和空间相对均匀 FSS 的正确条件。如果最大摇臂角度保持小于临界翻转角（定义为流体自由表面与皿底外边缘相交的角度），则皿底仍被一层薄的培养基覆盖。中央 84%和 50%皿底内的峰值 FSS 的空间变化分别限制在 41%和 17%以内。发现 FSS 的大小与流体粘度和最大摇臂角度成正比，与流体深度与长度比的平方和摇臂周期成反比。对于一个商用的矩形培养皿（长 37.6mm），当培养皿以 1 个周期/秒的速度摇臂+5 度时，预计皿底中心处的 FSS 将达到 0.9 dyn/cm²左右。我们的分析表明，如果控制得当，摇臂式“跷跷板”系统可以作为一种替代方法，为培养细胞提供低幅度、动态的 FSS。
