Microfluidics: A tool to control the degree of polydispersity

This contribution deals with a foam templating route to produce solid monodisperse chitosan foams via microfluidics. We firstly produced a monodisperse liquid foam from a 4 wt % chitosan solution. Subsequently, we cross-linked the chitosan with genipin and freeze-dried the resulting monodisperse foamed hydrogel to obtain solid monodisperse chitosan foams. In order to obtain a desired polydispersity we also used microfluidics, i.e. we produced polydisperse foams with a controlled bubble size distribution by applying a periodic pressure to the gas phase. The resulting polydisperse templates were cross-linked and solidified by the same procedures we used for the monodisperse chitosan foams, which, in turn, leads to solid polydisperse chitosan foams with a controlled polydispersity. Having control over both the bubble size and the polydispersity allowed us to study the influence of the pore size distribution on the mechanical properties since the generated solid foams have the same average pore size and the same composition (gas phase included). We focus our attention on the structure of the resulting solid monodisperse and polydisperse chitosan foams (SEM and μ-CT images) and on their compressive mechanical properties and discuss the differences between the two systems.