RII Track-4: NSF: Understanding Microstructure Evolution in Stimuli-Responsive Yield-Stress Fluid-Assisted 3D Printing: Linking Microstructures to Macroscale Rheological Properties

Recently, an innovative three-dimensional (3D) printing method has been proposed and developed to fabricate parts with arbitrary architectures. In this method, a 3D structure is freeform printed within a unique liquid support bath with desired properties that are controllable by either printing conditions or working environments. Although this method presents a better printing capability than many current 3D printing approaches, the working mechanisms of unique support bath materials are still elusive, which has hampered the further development of this 3D printing method.

The project aims to investigate the microstructure changes of a representative thermosensitive support bath material at different temperatures and printing conditions. The achievements of this project can guide the design of more support baths as well as fundamentally explain the working mechanisms of printing within a support bath. The proposed research will have a profound societal impact by accelerating the development of 3D printing technology to enhance the manufacturing capability in the United States.

In addition, the project will promote the education of students from K-12 to graduate in the State of Nevada through diverse activities, including hands-on K-12 lab activities, research module-involved curricula, and mentorship of students from underrepresented backgrounds at the University of Nevada, Reno.

This Research Infrastructure Improvement Track-4 EPSCoR Research Fellows (RII Track-4) project would provide a fellowship to an Assistant professor and training for a graduate student at the University of Nevada Reno (UNR). Stimuli-responsive yield-stress fluids, developed on the basis of regular yield-stress materials, can change rheological properties/behaviors by responding to both applied shear stress and external stimuli.

This dual-responsiveness makes stimuli-responsive yield-stress fluids promising for support bath-assisted 3D printing because a support bath material can be easily added during printing and removed after printing by applying external stimuli to achieve desired rheological properties, making it technically feasible to print 3D structures with arbitrary architectures. However, the interrelationships between microstructure evolution and macroscale rheology change of stimuli-responsive yield-stress fluids have so far remained elusive.

Thus, the overarching goal of this project is to fundamentally understand the microstructure evolution of a representative stimuli-responsive yield-stress fluid—Pluronic F127-nanoclay nanocomposite—under different stress and temperature conditions through nanoscale material characterization, mathematical modeling, molecular dynamics simulation, and rheological testing. To achieve this goal, two integrated research objectives will be pursued: (1) characterize/establish static microstructure models in Pluronic F127-nanoclay nanocomposite via nanoscale material characterization techniques and mathematical modeling; and (2) explore temperature- and stress-induced microstructure evolutions via molecular dynamics simulation and rheological property testing.

Completing the objectives will establish a paradigm for linking microstructures to macroscale rheological properties of support bath materials, promoting the development of more advanced stimuli-responsive yield-stress fluids for 3D printing applications in the future.

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.