Highly ordered biobased scaffolds: From liquid to solid foams

Abstract

We propose here a liquid foam templating route using microfluidic techniques to produce biobased monodisperse chitosan foams from aqueous chitosan solutions which are stabilized with a biobased sugar surfactant. The foaming solution contained 1.5 wt % chitosan and was stabilized by 0.1 wt % surfactant. We show how microfluidics allows for the generation of bubble sizes from 200 μm to 800 μm with the help of microfluidic chips with constrictions of different sizes. Due to the monodispersity of the resulting bubbles, highly ordered liquid foams are formed. We freeze-dried the non-cross-linked chitosan liquid foams to obtain solid chitosan foams. In addition, we also cross-linked the liquid templates by genipin, a natural cross-linker, via heating at 40 °C for 2 h. The aqueous cross-linked foams were dried, either by heating at 60 °C for 18 h or by freeze-drying. We found that the drying method, as well as whether the foams were cross-linked or not, have a tremendous influence on the morphology of the solid foams.