3D printing nanoparticles: An introduction
Stanford material engineers have pioneered a method to 3D print hard-to-manufacture nanoparticles. Consequently, this innovation could lead to materials that rapidly change their form.
Furthermore, the shape of nanoparticles plays a crucial role in determining their physical properties. “A crystal made of nano-ball bearings differs from one made of nano-dice, resulting in unique properties,” explained Wendy Gu, an assistant professor at Stanford. In her recent paper published in Nature Communications, she noted, “We’ve used 3D nanoprinting to create Archimedean truncated tetrahedrons, which are micron-scale tetrahedrons with cut-off tips.”
Self-Assembly and Phase Shifting
In addition, Gu and her team detailed their process for nanoprinting these challenging nanoparticles. They mixed the nanoparticles into a solution and observed them self-assemble into promising crystal structures. Importantly, these materials can shift between states in minutes. They rearrange into new geometric patterns through a process known as “phase shifting.” This process resembles atomic rearrangement, which can turn iron into tempered steel or enable data storage.
“If we can control these phase shifts in materials made of Archimedean truncated tetrahedrons, it could lead to significant advancements,” Gu stated.
Moreover, Archimedean truncated tetrahedrons (ATTs) have been highly sought after for their potential to create phase-changing materials. However, they were difficult to fabricate until recently. While Gu’s team is not the first to produce these nanoparticles, they are among the first to use 3D nanoprinting. “With 3D nanoprinting, we can precisely control particle shape,” Gu explained. “Simulations predict that this shape can form valuable structures with interesting properties.”
Desirable Geometric Structures of ATTs
ATTs can form two desirable geometric structures. First, a hexagonal pattern emerges when tetrahedrons rest flat with truncated tips pointing upward. Second, a crystalline quasi-diamond structure features alternating upward- and downward-facing tetrahedrons. This arrangement resembles eggs in a carton and is highly valuable in the photonics community, as it could spur new scientific discoveries.
Most importantly, materials made from 3D-printed particles can rearrange rapidly. They can switch between phases with the application of a magnetic field, electric current, heat, or other methods. This capability could lead to innovations, such as solar panel coatings that change throughout the day to maximize efficiency. Additionally, hydrophobic films for airplane wings and windows could prevent fogging or icing, while new types of computer memory could also emerge.
Future Research Directions
Currently, Gu’s latest research focuses on making these particles magnetic, allowing for further control over their behavior. “The possibilities are only beginning to be explored,” she concluded.
Reference: “Direct observation of phase transitions in truncated tetrahedral microparticles under quasi-2D confinement” by David Doan, John Kulikowski, and X. Wendy Gu, 25 March 2024, Nature Communications. DOI: 10.1038/s41467-024-46230-x