Direct ink writing of particle-based multiphase materials: From rheology to functionality

Direct ink writing (DIW) allows to produce complicated geometries by extruding material from a nozzle. The ink has to meet certain material requirements during and after printing for the object to be successfully produced. Meanwhile, the functionality requirements of the end-use application should be met. This paper attempts to provide the rheological basis and critical view to understand the material requirements for DIW inks and to help making the bridge between the rheology and printability of particle-based multiphase DIW inks while meeting the functional demands of the end product. Colloidal suspensions and Pickering emulsions are often used material classes for DIW. Some of the most important and noteworthy applications are described for both material classes. Thereafter, a more novel particle based multiphase system for DIW, namely capillary suspensions, is briefly discussed.