EM student wins Image of Research undergraduate competition

An engineering mechanics undergraduate student received first place in the campus’ Image of Research Undergraduate Research Competition.

The winning image – called “Surprising Dynamics of Hollow Droplet Impact on Solid Surfaces” – from Sawyer Eaton, an undergraduate researcher in MechSE Professor Jie Feng’s Fluids, Interfaces and Transport (FIT) Lab, came from a project focused on the impact dynamics of hollow droplets.

Droplet impact on solid surfaces plays a critical role in both natural and industrial contexts. For example, the collision of raindrops with leaves and soil influences the distribution of water and contaminants in the environment, while in advanced technological applications—such as inkjet printing—the precision of each microscopic ink droplet is crucial for producing high-quality images. Hollow droplets, composed of a gas bubble encapsulated by a liquid shell, exhibit a distinct core–shell structure that imparts unique physical and chemical properties compared to single-phase droplets. This morphology is prevalent in various practical processes, including raindrop impacts on the Earth's surface, the deposition of hollow spherical particles during thermal spray coating, and bubble-bursting aerosol transfer from the ocean. In many of these scenarios, the liquid shell can behave viscoelastically when the phase contains polymers, surfactants, or biological macromolecules commonly found in natural and industrial fluids. Despite its relevance, the impact dynamics of hollow droplets with viscoelastic coatings on solid surfaces have received limited attention. Feng and his researchers, including Eaton, are investigating this phenomenon to better understand and control the spreading and bouncing behavior of such droplets.

Eaton’s image illustrates the post-impact bouncing dynamics of hollow droplets with viscoelastic shells.

“We often overlook the little things in life; by their very nature it is simply more challenging for them to strike our attention,” Eaton wrote alongside his image submission. “However, as is often the case with the unassuming, when you decide to give them your attention, you will find an entire world of vibrant and exciting discoveries waiting to be made. Such was the case with my research on droplet impact, an unassuming phenomenon found in numerous natural and industrial processes, such as rainfall and additive manufacturing. As I dove into this phenomenon, I found that there exists a wide variety of striking and sometimes wild behaviors that droplets will partake in as they impact a surface. Often the droplet’s dynamics defy what I expect, even what seems physically possible. In these images of a progressing hollow non-Newtonian droplet impact, the droplet becomes a lava lamp-like tendril that looks to me like an otherworldly cyclops. Yet, as fantastic as the impact may seem, there is nothing at play besides the laws of physics. In this way, my research has been a lovely reminder that nature is full of wonder, if only you take the time to look for it, even in the places you may least expect.”

Eaton has worked in Feng's lab since summer 2024. Alongside a graduate student mentor, he has helped iteratively design their research methods and apparatus.

“While I have learned a lot about the science relating to the project, I think the more important things I have learned pertain to the broader topic of how to conduct research. I am starting grad school next fall, and familiarizing myself with this experience has made me much more comfortable and excited about conducting research in the future,” Eaton said.