![]() Anisotropic, sometimes ‘hairy’, fluid gel particles have been found in a number of studies this is in contrast with other studies where very small, spherical fluid gel particles were produced. These variables will influence the size, shape and number of fluid gel particles created and therefore their measureable properties, crucially their rheological and thermal behaviour. Factors influencing fluid gel production include the shearing method (Couette or cone and plate geometries in a rheometer, jacketed pin stirrer, overhead impeller or magnetic flea), shear rate, cooling rate, biopolymer type and concentration and ion concentration, if required. ![]() This has been described in the literature for thermoreversible biopolymer solutions, including mixed systems, but also biopolymers which undergo gelation mediated to some extent by ions. The term fluid gel describes the suspension of microgel particles created when sufficient shear is applied to a gelling biopolymer solution through its gelation, as opposed to allowing the solution to gel quiescently. If the nozzle prints at different temperatures for each layer a structure with modulated texture could be created. This allows the use of ambient temperature feedstocks and by altering the nozzle temperature, the internal nature (presence or absence of gel particles) and gel strength of printed droplets differs. Using this principle, for the first time fluid gels have been applied to a high viscosity 3D printing process wherein the printing temperature (at the nozzle) is controllable. As agar gelation is thermoreversible this type of fluid gel is able to be heated again to melt agar gel particles to varying degrees then re-form a network quiescently upon cooling, whose strength depends on the temperature of re-heating, determining the amount of agar solubilised and subsequently able to partake in re-gelation. Suspensions of gel particles which are pourable or spoonable at room temperature can be created by shearing a gelling biopolymer through its gelation (thermal or ion mediated) rather than allowing quiescent cooling – thus the term ‘fluid gel’ may be used to describe the resulting material.
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