Application Guide
How porosity, pore size, and interconnectivity of tissue-engineering scaffolds, porous implant coatings, and bone grafts are characterized — and why micro-CT often complements or replaces mercury intrusion.
Scaffolds for tissue engineering must let cells migrate in, let nutrients and waste diffuse, and allow blood vessels to form — all of which depend on pore size and, above all, on how well the pores are interconnected. For bone scaffolds, pore sizes of roughly 100 µm and above are generally considered necessary for bone ingrowth, and larger pores (often > 300 µm) are associated with better vascularization (Karageorgiou & Kaplan, Biomaterials, 2005). Higher porosity, however, lowers mechanical strength, so designs balance the two.
Porous coatings on orthopaedic implants, ceramic bone-graft substitutes, and drug-releasing matrices raise the same questions on smaller length scales.
| Property | Method | Strengths | Limitations |
|---|---|---|---|
| Pore size, strut thickness, interconnectivity (3D) | Micro-computed tomography (micro-CT) | Non-destructive; measures pore bodies and connections directly | Resolution limited to a few µm; threshold choice affects results |
| Pore-throat size distribution, open porosity | Mercury intrusion | Wide size range down to nanometres | Measures throats, not bodies; compresses soft polymers; destructive |
| Total porosity | Gravimetric (mass, volume, material density) or helium pycnometry + envelope volume | Simple and robust | No size information |
| Surface area / nanoporosity of ceramics | N2 or Kr adsorption, BET | Relevant to protein adsorption and degradation | Little information on macropores |
| Hydrated structure (hydrogels) | Cryo-SEM, confocal microscopy, swelling ratio | Images the wet state | Freeze-drying for MIP/SEM creates artefacts |
Total porosity is usually calculated as ε = 1 − ρapparent / ρmaterial, where the apparent density comes from the scaffold mass and its external volume.
Use the calculators to convert test pressures to pore sizes, or email a short description of your sample and what you need to measure.