Liquid foam templating – A short review

INTRODUCTION TO LIQUID FOAM TEMPLATING

Foams are gas bubbles dispersed in a liquid (aqueous foams) or in a solid matrix (polymer foams). Polymer foams are used in a wide range of applications due to their light weight and a high specific surface area compared to other materials. Solid foams, like other porous materials, can serve as an open-cell scaffold for tissue engineering [1]. For such a material, the pore size and polydispersity are key parameters in cell colonization [2-4]. The optimal pore size is dependent upon the kind of cell cultivated. Therefore, there is a clear need for techniques enabling an effective tuning of the scaffold pore size. Here, liquid foam templating based on the translation of a liquid template into a solidified version of its initial liquid structure, is employed to tailor the resulting porous solid foam morphology [5].

KEY FINDINGS

This work introduces a new route towards tailoring effectively with microfluidics the generation of fully biobased and highly ordered solid foams via liquid foam templating. The foam was generated within the microfluidic devices by co-injection of nitrogen and foaming solution containing both Chitosan and Genipin (biobased polymer and cross-linker respectively).

Both COC (Cyclic Olefin Copolymer) and glass flow-focusing chips were employed to generate bubble diameters ranging from 200 to 800 µm via microfluidics bubbling as represented in Fig 1.

The fluids flow rates were controlled with Elveflow’s OB1 pressure-driven flow controller connected to a nitrogen tank as illustrated in Fig.2.

The liquid foam was collected in a polystyrene Petri dish and cross-linked at 40°C for 2 hours. The resulting foam was further solidified and dried either via freeze-drying or by placing it at 60°C for 18 hours.

The author produced both highly monodisperse liquid and resulting solid foams with a polydispersity index varying from 2.9% up to 3.5% as described in Fig 3 and Fig 4.

References