In science and engineering, impressive technical feats sometimes draw on the arts—such is the case for a new study in Nature.
First author Ahyoung Kim started taking pottery classes during the second year of her doctoral program simply to have fun. She never expected to learn a skill that would inspire a new technique for precisely manufacturing virus-sized building blocks, called nanoparticles, for designer materials with unique properties.
"When you are immersed in the science, there are parts of your projects that you cannot see," said Kim, who is a doctoral graduate of materials science and engineering at the University of Illinois. "But when you are doing some other activities, that smears in new ideas."
Kim often paints her pots when they come out of the kiln. She creates intricate designs by first applying a layer of wax that blocks paint from reaching the ceramic. With the waxy stencil in place, Kim can liberally apply paint to make the patterns she wants.
As a materials scientist, Kim develops methods for guiding nanoparticles into designed structures—with the aim of engineering material properties from the ground up. She works in the lab of corresponding author Qian Chen , professor of materials science and engineering at U-I and an expert of nanomaterial engineering at the University of Michigan's Center for Complex Particle Systems .
Kim's artwork inspired her and her labmate Chansong Kim, a doctoral student of materials science and engineering at U-I, to precisely paint select parts of nanoparticles with patches of molecules that protrude from the nanoparticles like hairs, modifying how the particles come together. The precision comes from using iodide like Kim's waxy stencils. Wherever the iodide attaches, the hairs cannot.
The hair-like molecules repel each other, so by precisely controlling where they attach, Kim, Chen and their collaborators at U-M and Penn State create nanoparticles that arrange themselves into larger crystals with more open space in their structures than were possible with other methods.
"One of the holy grails of nanoscience has been to make designer building blocks out of any material and then dictate exactly how they stick to each other," said Sharon Glotzer , the Stuart W. Churchill Collegiate Professor of Chemical Engineering at U-M, an expert on modeling and simulation of nanoparticles, a co-principal investigator of the Center for Complex Particle Systems and a co-corresponding author of the study.
"This stenciling method is super powerful because it provides a quantum leap in control over the building blocks' designs, so it means that more sophisticated materials from nanoparticles will become possible in the near future."
The arrangement of the building blocks often determine a material's properties, particularly how they interact with light. For instance, nanomaterials could potentially change color with changes in structure, allow microscopes to see objects smaller than wavelengths of visible light or enable cloaking devices.
To build materials with nanoparticles, scientists suspend the particles in a liquid, which then combine into a crystal lattice according to laws of chemistry and physics. Scientists can influence how the particles arrange themselves by changing the properties of the liquid or the shapes of the particles, but modifying nanoparticles' surfaces can unlock more complex crystal structures. Glotzer's previous work has suggested that adding patches of other molecules onto nanoparticles can help them arrange in ways not otherwise possible.
But controlling where the patches go has been a challenge for nanoscientists. Kim had successfully placed hair-like molecules strictly on the corners of gold, triangular nanoparticles , but she couldn't reproduce the same level of control for other nanoparticle shapes. After diving into older studies, Kim realized that the mask-like chemical was iodide, which is normally used to shape gold nanoparticles. But to use iodide as a stencil, she needed to control its placement.
For help, Kim turned to Kristen Fichthorn , the Merrell Fenske Professor of Chemical Engineering at Penn State University, a U-M doctoral graduate in chemical engineering and a co-corresponding author of the study. Fichthorn created quantum-mechanical models of Kim's nanomaterials to predict how their surface atoms react with other chemicals. The models suggested that reproducible stenciling patterns could be made by controlling the ratio of iodide to 2-naphthalenethiol, a molecule that links the nanoparticles to the hair-like molecules.
To ensure the hairs would attach to the linkers, Tommy Waltmann, a U-M doctoral graduate in physics and scientific computing and co-first author of the study, created computer simulations that showed how the hairy appendages fit onto the spaces coated by the linker molecules, and how the resulting patchy particles assembled into crystal lattices. The simulations provided a blueprint for making a large collection of nanoparticles with a variety of shapes and hairy patch patterns.
"That 'a-ha' moment where the simulation actually mirrors what we see in the experiments is always very rewarding," Waltmann said.
The research was funded by the U.S. Department of Energy, the U.S. Department of Defense, the National Science Foundation and the Office of Naval Research.
Kim is now a postdoctoral fellow at Caltech's Kavli Nanoscience Institute. Glotzer is also the John Werner Cahn Distinguished University Professor of Engineering, as well as a professor of materials science and engineering and physics. Fichthorn is also a professor of physics.
Study: Patchy nanoparticles by atomic stencilling (DOI: 10.1038/s41586-025-09605-8)
