Safinia Laleh, Mantalaris Athanasios, Bismarck Alexander
Department of Chemical Engineering, Polymer & Composite Engineering (PaCE) Group, Imperial College London, South Kensington Campus, London, SW7 2AZ United Kingdom.
Langmuir. 2006 Mar 28;22(7):3235-42. doi: 10.1021/la051762g.
Polymer scaffolds tailored for tissue engineering applications possessing the desired pore structure require reproducible fabrication techniques. Nondestructive, quantitative methods for pore characterization are required to determine the pore size and its distribution. In this study, a promising alternative to traditional pore size characterization techniques is presented. We introduce a quantitative, nondestructive and inexpensive method to determine the pore size distribution of large soft porous solids based on the on the displacement of a liquid, that spreads without limits though a porous medium, by nitrogen. The capillary pressure is measured and related to the pore sizes as well as the pore size distribution of the narrowest bottlenecks of the largest interconnected pores in a porous medium. The measured pore diameters correspond to the narrowest bottleneck of the largest pores connecting the bottom with the top surface of a given porous solid. The applicability and reproducibility of the breakthrough technique is demonstrated on two polyurethane foams, manufactured using the thermally induced phase separation (TIPS) process, with almost identical overall porosity (60-70%) but very different pore morphology. By selecting different quenching temperatures to induce polymer phase separation, the pore structure could be regulated while maintaining the overall porosity. Depending on the quenching temperature, the foams exhibited either longitudinally oriented tubular macropores interconnected with micropores or independent macropores connected to adjacent pores via openings in the pore walls. The pore size and its distribution obtained by the breakthrough test were in excellent agreement to conventional characterization techniques, such as scanning electron microscopy combined with image analysis, BET technique, and mercury intrusion porosimetry. This technique is suitable for the characterization of the micro- and macropore structure of soft porous solids intended for tissue engineering applications. The method is sensitive for the smallest bottlenecks of the largest continuous pores throughout the scaffold that contributes to fluid flow.
为组织工程应用量身定制的、具有所需孔隙结构的聚合物支架需要可重复的制造技术。需要无损、定量的孔隙表征方法来确定孔径及其分布。在本研究中，提出了一种有前景的替代传统孔径表征技术的方法。我们介绍了一种基于液体位移的定量、无损且廉价的方法，该液体通过氮气在多孔介质中无限制地扩散，以此来确定大型软质多孔固体的孔径分布。测量毛细管压力，并将其与孔径以及多孔介质中最大连通孔最窄瓶颈处的孔径分布相关联。所测量的孔径对应于连接给定多孔固体底部与顶面的最大孔的最窄瓶颈。在两种使用热致相分离（TIPS）工艺制造的聚氨酯泡沫上证明了突破技术的适用性和可重复性，这两种泡沫具有几乎相同的总孔隙率（60 - 70%）但孔隙形态非常不同。通过选择不同的淬火温度来诱导聚合物相分离，可以在保持总孔隙率的同时调节孔隙结构。根据淬火温度的不同，泡沫表现出纵向排列的管状大孔与微孔相互连通，或者是通过孔壁上的开口与相邻孔相连的独立大孔。通过突破试验获得的孔径及其分布与传统表征技术（如结合图像分析的扫描电子显微镜、BET技术和压汞孔隙率测定法）非常吻合。该技术适用于表征用于组织工程应用的软质多孔固体的微孔和大孔结构。该方法对整个支架中最大连续孔的最小瓶颈敏感，这些瓶颈有助于流体流动。
