Additive Manufacturing With Conductive, Viscoelastic Polymer Composites: Direct-Ink-Writing of Electrolytic and Anodic Poly(Ethylene Oxide) Composites

Abstract

Conductive viscoelastic polymer composites (CVPCs) consisting of conductive fillers in viscoelastic polymer matrices find numerous applications in emerging technologies such as flexible electronics, energy storage, and biochemical sensing. Additive manufacturing methods at micro- and mesoscales provide exciting opportunities toward realizing the unique capabilities of such material systems. In this paper, we study the direct-ink-writing (DIW) process of CVPCs consisting of electrically conductive additives in a poly(ethylene oxide) (PEO) matrix. We particularly focus on the deposition mechanisms of the DIW process and the influence of these mechanisms on the printed structure geometry, morphology, and functional properties. To this end, we utilized a novel practical approach of modeling the ink extrusion through the nozzles considering the non-Newtonian viscous effects while capturing the viscoelastic extensional flow (drawing) effects through the variation of the nozzle exit pressure. We concluded that inks containing higher amounts of high molecular weight (HMW) PEO exhibit drawing type deposition at high printing speeds and low inlet pressures enabling thinner, higher aspect ratio structures with ideal three-dimensional stacking. Under this deposition mechanism, the electrical conductivity of the anodic structures decreased with increasing printing speed, indicating the effect of the drawing mechanism on the printed structure morphology.