| Abstract
| - Polymer scaffolds tailored for tissue engineering applications possessing the desired pore structure require reproduciblefabrication techniques. Nondestructive, quantitative methods for pore characterization are required to determine thepore size and its distribution. In this study, a promising alternative to traditional pore size characterization techniquesis presented. We introduce a quantitative, nondestructive and inexpensive method to determine the pore size distributionof large soft porous solids based on the on the displacement of a liquid, that spreads without limits though a porousmedium, by nitrogen. The capillary pressure is measured and related to the pore sizes as well as the pore sizedistribution of the narrowest bottlenecks of the largest interconnected pores in a porous medium. The measured porediameters correspond to the narrowest bottleneck of the largest pores connecting the bottom with the top surface ofa given porous solid. The applicability and reproducibility of the breakthrough technique is demonstrated on twopolyurethane foams, manufactured using the thermally induced phase separation (TIPS) process, with almost identicaloverall porosity (60−70%) but very different pore morphology. By selecting different quenching temperatures toinduce polymer phase separation, the pore structure could be regulated while maintaining the overall porosity. Dependingon the quenching temperature, the foams exhibited either longitudinally oriented tubular macropores interconnectedwith micropores or independent macropores connected to adjacent pores via openings in the pore walls. The pore sizeand its distribution obtained by the breakthrough test were in excellent agreement to conventional characterizationtechniques, such as scanning electron microscopy combined with image analysis, BET technique, and mercury intrusionporosimetry. This technique is suitable for the characterization of the micro- and macropore structure of soft poroussolids intended for tissue engineering applications. The method is sensitive for the smallest bottlenecks of the largestcontinuous pores throughout the scaffold that contributes to fluid flow.
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