ERI: Direct Ink Writing of Nanocomposites of High Viscosity Rubber with Fillers

Direct ink writing is an additive manufacturing technique used to fabricate three-dimensional structures by precisely depositing and patterning materials in a layer-by-layer fashion. In direct ink writing, a material, typically a paste or a viscous ink, is extruded through a fine nozzle or syringe tip onto a substrate according to a computer-controlled path.

This manufacturing process is particularly well-suited for materials with high viscosity or those containing particulate fillers, such as polymers, ceramics, and composites. However, there is a critical knowledge gap in understanding the intricate relationships between feedstock material composition, additive manufacturing process parameters, resulting microstructures, and the properties of the manufactured parts.

This Engineering Research Initiation (ERI) award supports fundamental research to address this gap by investigating material-process-microstructure-property relationships in direct ink writing of high-viscosity rubber nanocomposites with fillers. Such materials, with their unique blend of flexibility, durability, and enhanced mechanical and electrical properties have extensive applications in the manufacturing of medical devices, soft robotics, automotive components, flexible sensors, and electronics, among other products that could benefit society and the economy.

The project also aims to advance educational and diversity initiatives by actively engaging students from underrepresented minority groups, including women, first-generation college students, and ethnic minorities, in hands-on experiences with advanced technologies and cutting-edge research.

The overarching goal of this project is to advance the understanding of material-process-microstructure-property relationships in the direct ink writing of highly viscous rubber nanocomposites to optimize both material composition and process parameters to achieve high-quality manufactured parts. This will be achieved through three main tasks: 1) Preparation of high molecular weight liquid isoprene rubber compounds with various reinforced fillers such as silica or carbon black, and conductive fillers such as conductive carbon black, carbon nanotubes, or graphene nanoplatelets, followed by rheometric analysis to characterize viscosity and flow at varying shear rates and temperatures; 2) Systematic variation of the manufacturing process parameters such as nozzle diameter and temperature, print speed, and infill angle, within processes constraints established by rheological analysis, to investigate the influences of these parameters on microstructure and defect formation, as captured by high-resolution optical and scanning electron microscopy; 3) Experimental investigation of mechanical, electromechanical, and time-dependent behaviors of 3D-printed samples to understand the correlation between microstructural features and macroscopic properties.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.