Session: Research Posters

Paper Number: 120315

120315 - Investigating the Influence of Nanoparticle Size and Loading on Printability of Polymer-Nanoparticle Composite Inks for Direct Ink Writing 

Direct ink writing (DIW) is an innovative and inclusive 3D printing technology that offers tremendous potential for fabricating intricate structures with diverse mechanical properties and functionalities. By blending polymers with different nanoparticles, DIW allows for the creation of tailored 3D objects, spanning a wide range of applications from biomedical engineering to electronics. However, a critical aspect of the DIW process lies in the development of printable inks that exhibit optimal performance and reliability. Although significant progress has been made in formulating ink recipes by exploring various combinations of nanoparticles, polymers, and solvents, there are still two fundamental questions that have yet to be fully addressed: 1) how can we accurately assess the printability of an ink, and 2) what is the influence of nanoparticle size and loading on the printability of DIW inks? To bridge this knowledge gap and provide valuable insights, this study focuses on the SiO2 nanoparticle-Polydimethylsiloxane (PDMS) system as a model system. Three commonly used printability analysis methods, namely dual-layer printing analysis, ink rheology, and printing line width analysis, are rigorously employed and systematically evaluated. These methods serve as effective tools to investigate the relationship between nanoparticle characteristics and ink printability. Through comprehensive comparisons, it is evident that dual-layer printing analysis (DLPA) stands out as the most direct and reliable method for evaluating ink printability. By analyzing the merging behavior of two vertically stacked printing layers, DLPA offers valuable information regarding the interlayer interaction and the overall quality of the printed structure. The printability factor (Pr) derived from DLPA serves as a quantitative metric, with a Pr value approaching 1 indicating minimal merging between layers and excellent printability. In this study, an empirical critical value of Pr = 0.9 is established as the threshold for defining a printable ink. Further analysis reveals intriguing trends related to nanoparticle size and loading. Smaller nanoparticles, such as those with a diameter of 26 nm, require a relatively low loading of 2.91 wt.% to achieve the critical printability threshold. Conversely, larger nanoparticles (847 nm) necessitate a significantly higher loading of 28.57 wt.% to attain the same level of printability. It is worth noting that increasing the particle size generally enhances the printability factor (Pr), indicating improved ink flow and reduced merging between adjacent printed layers. However, there exists an upper limit to particle size due to practical constraints imposed by the fixed printing pressure and nozzle size.

Remarkably, the study also reveals the highest achievable particle loading, which is 66.7 wt.% for 847 nm nanoparticles under specific printing conditions, including a printing pressure of 120 psi and a nozzle diameter of 300 μm. These findings highlight the potential of using nanoparticles to tailor DIW materials, allowing for the creation of a broad spectrum of products ranging from soft, bio-compatible gels to high-strength ceramics. Moreover, the comparison of different analysis methods underscores the need for developing standardized evaluation criteria to assess printability across diverse ink formulations and printing processes. Establishing generic standards will facilitate the broader adoption of DIW technology and streamline the development of printable inks with consistent and predictable performance.

In summary, this study significantly contributes to the understanding of the DIW process by elucidating the influence of nanoparticle size and loading on ink printability. The insights gained from this research provide a solid foundation for the development of advanced DIW materials and pave the way for the utilization of DIW technology in a wide range of industries and applications.

Presenting Author: Yun Li Villanova University

Presenting Author Biography: PhD student of Hybrid Nano-Architectures and Advanced Manufacturing Laboratory, Department of Mechanical Engineering, Villanova University

Authors:

Yun Li Villanova University
Aidan Flynn Villanova University
Christopher Masternick Villanova University
Brandon Kolanovic Villanova University
Bin Li Wichita State University
Liang Zhao Villanova University
Mingyuan Sun Villanova University
Bo Li Villanova University