Q: What initially drew you to the APS? 

Yanfei: I first learned about the APS through both collaborations and the scientific literature. Many of the studies I was following relied on synchrotron techniques, and collaborators were also using the APS, which made it clear how valuable it could be for my research.

My work focuses on heat and charge transport in materials, particularly polymers, where thermal management is critical for performance and safety.

What drew me to the APS was its ability to probe material structure at high resolution. Understanding how heat moves through a solid material requires insight into how atoms and molecular chains are arranged, and the APS provides a way to access that information across multiple length scales.
 

Q: Can you describe the research you’ve conducted at the APS?  

Yanfei: My research at the APS focuses on how heat and energy move through polymer-based materials and their related structures. Polymers are widely used because they are lightweight and electrically insulating, but they are typically poor thermal conductors. A key question in my work is how to improve thermal transport while maintaining these properties.

To address this, we study how structure at different length scales influences thermal behavior. Unlike metals or crystals, polymers are often disordered, with chains that are entangled and arranged in complex ways, which makes their structure difficult to characterize.

At the APS, we use X-ray scattering techniques, including wide-angle, small-angle, and grazing-incidence X-ray scattering, to probe how polymer chains are packed and how disorder is distributed. These measurements allow us to connect microscopic structure to thermal properties in ways that are not possible with conventional laboratory tools.
 

Q: What role did the APS play in enabling or advancing your work?  

Yanfei: The APS has been essential because of its brightness and resolution, which allow us to detect structural features that are otherwise difficult to measure. For polymer systems, where much of the structure is disordered, this level of sensitivity is especially important.

Using APS beamlines, we’ve been able to study how polymer structure evolves across different processing and structural conditions, from bulk polymers to 100nm thin films. This has helped us explore how atomic vibrations and molecular arrangements influence heat transport.

The APS also enables temperature-controlled X-ray experiments, allowing us to directly observe how structural changes at different temperatures affect thermal transport. These capabilities provide a more complete picture of how materials behave and how their properties can be tuned.
 

Q: Has anything unexpected come out of your work with the APS, either in your results or in the process itself? 

Yanfei: One of the most surprising findings in our work has been the role of disorder in polymer materials. While crystallinity and chain alignment are known to influence thermal transport, we experimentally found that relatively small variations in amorphous disorder can lead to significant differences in how heat moves through a material.

This was unexpected, because thermal transport in polymers has more often been interpreted through crystallinity and chain alignment, rather than subtle variations in amorphous disorder. Using APS measurements, we were able to directly observe these variations and link them to changes in thermal behavior.

We’ve also seen how interfaces in composite materials, such as polymers with added fillers, introduce additional complexity. Our experimental studies suggest that interfacial defects can, in some cases, enhance thermal transport across these boundaries. These interfaces can strongly influence heat transport, and synchrotron measurements have helped us better understand how structure at these boundaries affects performance.
 

Q: What impact has your research at the APS had on your work so far? What are you excited about exploring next? 

Yanfei: The APS has played an important role in advancing our understanding of structure-property relationships in polymers. By enabling detailed structural measurements, it has helped us better understand how microscopic features influence thermal transport in disordered materials.

Looking ahead, we are focused on combining experimental measurements with modeling and simulation to design materials with tailored thermal properties that do not yet exist, particularly for applications such as electronics cooling and energy systems.

More broadly, I’m excited about continuing to explore how advanced characterization tools can reveal new insights into complex materials.