Colloidal Inks for Directed Assembly of 3-D Periodic Structures

Abstract

Mesoscale periodic structures have been fabricated via directed assembly of colloidal inks. Concentrated colloidal gels with tailored viscoelastic properties were designed to form self-supporting features. The inks were deposited in a layer-by-layer sequence to directly write the desired 3-D pattern. Periodic structures with spanning features that vary between ∼100 μm and 1 mm were assembled. Shear rate profiles were calculated on the basis of the measured rheological properties of the inks under slip and no-slip boundary conditions during flow through a cylindrical deposition nozzle. Deflection measurements of spanning elements were used to probe the relationship between gel strength, deposition speed, and shear rate profiles in the nozzle. These observations revealed that the ink adopted a rigid (gel) core−fluid shell architecture during assembly, which simultaneously facilitated bonding and shape retention of the deposited elements.