Thermoreversible gels – optimisation of processing parameters in fused deposition modelling

Thermoreversible hydrogels are widely used in foods, drug delivery and tissue engineering. Novel shapes/textures out of them are being increasingly fabricated using Fused Deposition Modelling (FDM) type 3D printing, where gels are extruded layer-by-layer above their gelling temperature followed by cooling. It is crucial to develop a library of suitable materials and optimise printing conditions to ensure good print quality and to minimise damage to the embedded active components (cells, flavours, nutrients and drug molecules). Several mixtures of gelatin with gellan and agar were prepared and characterised. They were formed into cylinders using FDM at four different temperatures and three different speeds. The printed specimens were tested for their mechanical properties using compression. The fidelity of printed shapes and the inter-layer adhesion appeared to rely on the cooling required before approaching the gelling temperature and the time available for it, through printing speed. A generic printability diagram was constructed for navigating to the optimal printing conditions for a given formulation.