Cellulose scaffolds with an aligned and open porosity fabricated via ice-templating

Regenerated cellulose scaffolds with an aligned, columnar and open porosity were fabricated by an ice-templating process. For this purpose, cellulose dissolved in the non-derivatizing aqueous solvent NaOH/urea was used. This cellulose solution was frozen from the bottom side of the mold leading to a directional heat flow in only one direction. Consequently, the directional solidification leads to a directional ice crystal growth. The ice crystals grow as aligned columns repelling and enriching the cellulose molecules between them. After a complete solidification and sublimation of the ice crystals, which act as a sacrificial phase, a structured porous cellulose network is achieved. The scaffold was analysed by light microscopy and X-ray diffraction. The pore sizes in the scaffold can be adjusted by the processing conditions. However, an approach for structural control which is only based on the solution of the heat conduction equation and which was found to be appropriate for ceramic suspensions has only limited suitability for cellulose solutions. In the case of cellulose solutions the diffusion and redistribution of solutes seem to be of significant impact and have to be considered in an adapted model.