Title: Development of advanced composite materials by additive manufacturing

Abstract

Development of novel composite materials compatible with additive manufacturing while satisfying multifunctionality and cost for end-use applications is an urgent need to address limited materials available for AM. In this research, we developed novel nanocomposite materials based on zirconia bioceramic embedded in polymer matrix compatible with a customized material Jetting system. This new generation in-house developed MJ system is one of the scarce 3Dprinters of its kind which enables high-speed 3Dprinting (20 times faster than the current extrusion/jetting AM methods) of high viscous inks (upto 107 mPa.s). By inserting additives/surfactants to different amounts of photocurable polymers and Zr nanopowders, tailoring the rheology/feedstock concentration, and optimizing the printing parameters, we innovatively prepared a suitable feedstock for MJ printing and troubleshot arisen printing issues (e.g. nozzle clogging and Zr nanoparticles inhomogeneity in the polymer matrix), which are among the most significant challenges of developing compatible composite materials for extrusion-based 3Dprinting. A two-step sintering was developed to burn out the polymers, shrink the porosities, and obtain densified crack-free Zr components with high mechanical/structural properties to meet the demanding requirements as dental restorations. The exciting results stemming from this work inspired another research on developing a conductive polymeric composite including silicone (matrix) and carbon fiber (filler) for 3Dprinting of flexible wearable sensor for health monitoring applications. Feedstock concentration and printing parameters were optimized to attain printability, curability, and electrical properties of the feedstock. Particularly, carbon fiber loading and aspect ratio were optimized to attain the lowest percolation threshold and good electrical conductivity while prohibiting nozzle clogging issue. A number of potential applications of developed composite sensors including human motion detection such as finger movements and bending at the arm were evaluated. The outcomes showed significant innovative advancements in filling the gaps in current state-of-the-art to develop compatible composite materials for AM for biomedical applications.