University engineers conducted a study about how nonuniform synthetic particles assemble and found it happens in numerous phases, which opens opportunities for new uses of reconfigurable materials in technologies, such as solar cells and catalysis.

John Smith, graduate student in Engineering, said he and his team are trying to find new ways to use little particles to build to more complex structures.

“It is like chemistry, but instead of atoms, we are using particles,” Smith said. “What is special about this particular work is to find a way to put together these particles that are a little messy in order.”

Smith and other graduate students started by using these particles and found they could turn on and off how they interact with each other.

“You can decide one day they are attracted to each other; one day they are not attracted to each other,” Smith said. “They are like magnets, but they are not attracted to each other. So what we did is, we found the right conditions to get them to attract each other and build the structure that we are going for.”

There were qualitative studies of this phenomenon, but Smith and his team treated it more quantitatively, and they were able to learn more about what comes in between individual building blocks and the actual structure.

“(We wanted to know) how they come together and move around in the process,” Smith said. “That has a lot more information on how you can control what is going on.”

Ahyoung Kim, Engineering graduate student and co-author of the study, said people have seen this type of work before but have never seen the hierarchical structure.

“People only saw the assembly structure. Before there (was) only (a) linear assembly,” Kim said.

To get to these findings, they used a microscope to watch the process. This is where most of the data came from. Smith described it as a “movie” of the assembly process, and combined with this, he modeled how these interactions change when particles are of different distances or rotations.

“(Through this), we were able to describe what happens in the process,” Smith said.

In terms of applications, Smith said nanoparticles have electronic and optical properties important to consider.

“For a long time, people have been trying to use small particles for (different) toys; that means new electronic devices, computers, etc.,” Smith said. “One special thing about this is we don’t have a big material that we cut into tiny pieces for our device. It is more like we are able to use building blocks … to build it for us.”

Funds for the research came from the National Science Foundation, Kim said. 

The team has been working on the project for about two years and in the future, they will see how the phenomenon changes when started with different building blocks. 

“This project is almost wrapped up, but in the future, we can think about branching into different building blocks,” Smith said. 

[email protected]