Investigation of Rheology and 3D Printability of PDMS Nanocomposites Ink

Pristine polymers, when extruded for 3D printing purposes, often lack the ability to hold their shape after deposition due to insufficient yield stress, spreading as they wet on the deposited surface almost immediately upon exiting the nozzle. However, the addition of fillers, such as silica, can alter an ink’s rheological properties, viscoelastic properties, and shear thinning behavior, while endowing the ink with the yield stress and thixotropic behavior to hold its shape upon printing. With the addition of conductive nanofillers, such as carbon nanotubes (CNTs), these polymer-based nanocomposites can be used as 3D printable, functional inks. In this work, we study the effects of silicon-based nanofillers, on rheological behavior and 3D printability of PDMS/CNT nanocomposites. The shear thinning properties and yield point of the nanocomposite at various filler content is explored via peak hold and amplitude sweep tests, respectively. To explore the effects of the fillers on the 3D printing of the functional ink, multi-layered geometries are printed and studied under scanning electron microscopy (SEM). These images show the shape of each stacked layer and provide insight on the controllability of the print and the bonding of each layer to its adjacent. Studying the effect of fillers on the 3D printability of polymer-based functional inks is valuable, as these inks allow for the quick and facile generation of custom multifunctional structures for use in a wide array of applications.