Embedded direct ink writing of freeform ceramic components

Direct ink writing, a widely used additive manufacturing technique, has some disadvantages in fabricating suspended ceramic structures due to instabilities in the ink caused by surface tension and gravity forces, requiring a strict optimization of the rheology of the feedstock. To overcome this problem, freeform 3D printing was achieved in this work by performing printing inside a supporting medium composed of vegetable oil and fumed silica. The rheological properties of the supporting medium as well as the printability of the ink as a function of the solid content were investigated. Printing parameters such as gas pressure and nozzle movement speed were optimized for a selected diameter of the printed filament. With this method, several suspended structures were fabricated, such as coils with different pitches, hollow cylinders and 3D letters, showing no shape distorting both after printing and the thermal treatment. A preceramic polymer was used as the primary material for the tests, but we also demonstrated that with this approach it is possible to print using inks containing either metal or ceramic powders, thereby showcasing the large potential of this approach for being used in different applications.