1.1 本指南描述了适用于测定多孔组织支架的平均达西渗透系数的试验方法，该渗透系数是流体（通常为空气或水）根据施加的压力梯度流过支架的速率的量度。这些信息可用于优化组织支架的结构，开发一致的制造工艺，并用于质量保证目的。 1.2 该方法通常是无损和无污染的。 1.3 该方法不适用于容易变形或损坏的结构。通常需要进行一些实验来评估渗透性测试对特定材料/结构的适用性，并优化实验条件。 1.4 渗透性测量不应被视为多孔组织支架结构的确定指标，而应补充通过其他研究技术获得的测量结果，例如扫描电子显微镜、气流孔隙率测量和显微成像- 计算机X射线断层扫描（指南 F2450 , F2603 和 F3259 ). 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 本文件描述了获得由一系列相互连接的孔隙组成的结构的达西渗透系数平均值所需遵循的基本原则。 该系数是结构对流经结构的流体渗透性的度量，该渗透性由在结构上产生的压力梯度驱动。 4.2 该技术对封闭或盲孔的存在不敏感( 图1 ). 图1 组织支架中不同孔隙类型的示意图。流体通过开放的孔隙流过结构 4.3 渗透系数的值可用于比较制造样品的一致性，或确定改变一个或多个制造设置对渗透性的影响。它们也可用于评估组织支架的均匀性和各向异性。渗透系数的可变性也可以表示: 4.3.1 样品内部损坏，例如开裂或永久变形。 4.3.2 结构内存在大空隙，包括滞留气泡。 4.3.3 表面效应，例如制造过程中形成的皮肤。 4.3.4 可变样本几何体。 4.4 该试验方法基于以下假设，即在施加压力梯度的情况下，通过给定样品的流速随时间恒定。 注1: 如果未达到稳态流动条件，则可能是由于结构损坏（即，裂纹形成或多孔结构因流经其的流体施加在其上的力而变形）。由于流体流速高，弹性较差的结构也可能发生拉伸（弯曲）形式的样品变形。第节将更详细地讨论此主题 7. . 4.5 当使用水或其他水基液体作为渗透剂时，应注意确保疏水材料完全润湿。 4.6 通常，测量样品上产生的压差，作为流量增加和减少的函数。另一种可能更容易创建的方法是在样品上施加一系列不同的压差，并测量通过样品的流体的合成流量。 在流量增加后逐渐减少的完整循环中出现的滞后可以很好地衡量矩阵的行为一致性。流量增加和减少期间测得的压差显著滞后，表明结构中存在诱导损伤，材料表现为粘弹性，或遭受永久塑性变形。第节提供了一些关于如何确定这些因素中哪些是造成滞后的原因的指导 7. . 4.7 假设达西定律有效。这可以通过绘制通过试样的体积流量与通过试样的压差来确定。该图应为线性图，以应用达西定律，数据的最小二乘拟合应通过原点。这种曲线图是非线性的，这可能表明结构不符合达西定律或施加的压力范围过宽。 本主题将在第节中进一步讨论 7. .

1.1 This guide describes test methods suitable for determining the mean Darcy permeability coefficient for a porous tissue scaffold, which is a measure of the rate at which a fluid, typically air or water, flows through it in response to an applied pressure gradient. This information can be used to optimize the structure of tissue scaffolds, to develop a consistent manufacturing process, and for quality assurance purposes. 1.2 The method is generally nondestructive and non-contaminating. 1.3 The method is not suitable for structures that are easily deformed or damaged. Some experimentation is usually required to assess the suitability of permeability testing for a particular material/structure and to optimize the experimental conditions. 1.4 Measures of permeability should not be considered as definitive metrics of the structure of porous tissue scaffolds and should complement measures obtained by other investigative techniques, for example, scanning electron microscopy, gas flow porometry, and micro-computer X-ray tomography (Guides F2450 , F2603 , and F3259 ). 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 This document describes the basic principles that need to be followed to obtain a mean value of the Darcy permeability coefficient for structures that consist of a series of interconnected voids or pores. The coefficient is a measure of the permeability of the structure to fluid flowing through it that is driven by a pressure gradient created across it. 4.2 The technique is not sensitive to the presence of closed or blind-end pores ( Fig. 1 ). FIG. 1 Schematic of the Different Pores Types Found in Tissue Scaffolds. Fluid Flow Through the Structure is via the Open Pores 4.3 Values of the permeability coefficient can be used to compare the consistency of manufactured samples or to determine what the effect of changing one or more manufacturing settings has on permeability. They can also be used to assess the homogeneity and anisotropy of tissue scaffolds. Variability in the permeability coefficient can be also be indicative of: 4.3.1 Internal damage within the sample, for example, cracking or permanent deformation. 4.3.2 The presence of large voids, including trapped air bubbles, within the structure. 4.3.3 Surface effects such as a skin formed during manufacture. 4.3.4 Variable sample geometry. 4.4 This test method is based on the assumption that the flow rate through a given sample subjected to an applied pressure gradient is constant with time. Note 1: If a steady-state flow condition isn’t reached, then this could be due to structural damage (that is, crack formation or the porous structure deformed as a result of the force being placed upon it by the fluid flowing through it). Sample deformation in the form of stretching (bowing) can also occur for less resilient structures as a result of high fluid flow rates. This topic is discussed in more detail in Section 7 . 4.5 Care should be taken to ensure that hydrophobic materials are fully wetted out when using water or other aqueous-based liquids as permeants. 4.6 Conventionally, the pressure differential created across a sample is measured as a function of both increasing and decreasing flow rates. An alternative approach, which may be practically easier to create, is to apply a range of different pressure differentials across the sample and measure the resultant flow of fluid through it. The hysteresis that occurs during a complete cycle of increasing flow rate followed by a progressive decrease in flow rate can provide an excellent measure of the behavioural consistency of the matrix. Significant hysteresis in the measured pressure differential during increasing and decreasing flow rates can indicate the existence of induced damage in the structure, the fact that the material is behaving viscoelastically, or is suffering from permanent plastic deformation. Some guidance on how to identify which of these factors is responsible for hysteresis is provided in Section 7 . 4.7 It is assumed that Darcy’s law is valid. This can be established by plotting the volume flow through the specimen against the differential pressure drop across the specimen. This plot should be linear for Darcy’s law to apply and a least-squares fit to the data should pass through the origin. It is not uncommon for such plots to be nonlinear which may indicate that the structure does not obey Darcy’s law or that the range of pressures applied is too broad. This topic is further discussed in Section 7 .