Directed Colloidal Assembly of 3D Periodic Structures

Abstract

Colloidal inks, comprised of silica microspheres with tailored attractive interactions between them, have been directly assembled via a robotically controlled deposition technique. 3D periodic lattices, whose periodicity far exceeds the dimensions of the colloidal building blocks (see Figure for a cross‐sectional image), were created through layer‐ by‐layer patterning of parallel rods.

Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

“…The colloidal inks for robocasting should accomplish two key conditions [10,17,18]: shear thinning rheological behavior to enable extrusion through fi ne deposition nozzles with rapid recovery of yield stress after deposition, and high solids loadings to limit shrinkage and stress upon drying. As the surface of SiC, Al 2 O 3 and Y 2 O 3 particles must be covered with dispersant molecules, which govern the surface characteristics, in order to get similar zeta potential behavior for the three components, the spacing); a pre-shearing of 1 s -1 for a period of 60 s and a following equilibration (zero shear rate rest) time of 100 s were carried out before each test.…”

“…The retention of shape by the formed fi laments is basically accomplished by a precise control over the ink viscosity, employing high solids loadings for minimizing the shrinkage during the drying process and, thus, preventing cracking phenomena. In this way, robocasting has been proved suitable for many ceramics such as silica [17], alumina [18], tricalcium phosphate [19] or hydroxyapatite [20], all of which can be easily densifi ed in conventional furnaces in air atmospheres. Furthermore, the challenge of fabricating non-oxide ceramic scaffolds by robocasting has already been demonstrated [21], employing SiC inks containing submicronic SiC powders and 20 wt.…”

“…The Robocasting technique was originally developed as a rapid prototyping system for forming 3D-complex components by taking advantage of the knowledge on the colloidal processing of ceramics [10,17]. Robocasting consists in a concentrated colloidal ink (analogous to a slurry for a 3D printing process) extruded through a nozzle or tip forming a continuous fi lament, Concentrated ceramic inks based on -SiC powders, with different amounts of Y 2 O 3 and Al 2 O 3 as sintering aids, are developed for the adequate production of SiC scaffolds, with different patterned morphologies, by the Robocasting technique.…”

Rheological behavior of PMN gels for solid freeform fabrication

“…These methods were utilized previously for the controlled gelation of alumina, barium titanate, and lead zirconate titanate suspensions [6,[24][25][26][27][28]34]. In the first method, inks were prepared by adding poly(ethylene imine) (PEI) to the system.…”

“…It is a solid free form fabrication method that utilizes colloidal systems of low organic content [21][22][23]. Previously, Lewis and co-workers conducted intensive research on the robocasting of alumina [24], barium titanate [25] and lead zirconate titanate [26][27][28] powders and produced different geometries to be used in different applications [21].…”