Microwaves speed up producing scaffold foams with designed porosity from water glass

Abstract

Low-cost, porous, and mechanically resilient structures are required for bone replacement and tissue engineering applications. Numerous materials have been proposed, but few reached clinical efficacy. Starting from sodium silicate solution (water glass; WG), we developed a rapid fabrication route by microwave processing, yielding pure WG foams with high, tuneable porosity (up to 94%) and sizes of up to tens of centimetres within a few minutes. Based on experimental results and a physics-derived model description of the drying process we developed a phase diagram, offering a guideline to make WG foams with customised porosity. Combining X-ray diffraction, scanning electron microscopy and micro-computed tomography, we deduced relations between processing parameters, pore size, and pore size distribution. Pore diameters span 10 to 1000 μm, which is in the range required for the ingrowth of healthy bone. The compressive strength is equal or higher than the values reported for similar bioactive glass foams. The degradation tests in simulated body fluid showed promising bioactivity and biodegradation. Together with the purity of the material, lacking any additives, the WG foams are attractive for biomedical applications.

Keywords

• Sodium silicate
• Water glass
• Glass foam
• Microwave foaming
• Scaffold
• Mechanical property