Meet Our Grad Student Scholars is a series from Illinois-Indiana Sea Grant (IISG) celebrating the students and research funded by our scholars program. To learn more about our faculty and graduate student funding opportunities, visit Fellowships & Scholarships. 

Diana Alejandra Narvaez is a PhD student at Purdue University in the School of Engineering Technology working with soft materials and additive manufacturing to create a prototype of a new type of lake wave energy harvester, ultimately aiming to use this technology to collect aquatic energy that can power electronics in freshwater environments.

This project started with something simple: I wanted a flexible material that could also act as a sensor. 

At first, the team tried using a commercial conductive Tensor Processing Unit foam, specifically Filaflex, and printing it with fuse deposition modeling, a common 3D printing method. In theory, it sounded perfect—print a flexible structure and get an electrical response at the same time.

In practice, it was not that simple. Controlling the thickness was tricky, and the resistive response was not as consistent as I needed. Small changes in printing conditions would affect the signal, and it became difficult to rely on the results.

So, we changed the approach. Instead of printing everything, we moved to making the sensing material directly in the lab. This meant working with a semi-liquid substance that could be deposited more precisely, closer to screen printing, so we could get thinner layers and better contact with the substrate.

That worked well. The signal was cleaner, and the material behaved much more consistently.

Then we ran into another issue. The way we were processing those materials involved solvents that were unpleasant to work with, not just inconvenient, but also not ideal from a safety and repeatability standpoint.

Diana Narvaez presents at the American Society of Mechanical Engineers ASME SMASIS conference about her research of soft materials and sensing.

So again, we adjusted. We looked for a polymer matrix that could give us flexibility, but be easier and safer to work with. That’s what led us to waterborne polyurethane (WPU).

Switching to WPU made a big difference. Because it’s processed in water-based systems, WPU is much easier to handle and control. We could tune the material more effectively, adjusting concentration, stiffness, and overall response, without dealing with harsh solvents.

And importantly, it still gave us what we needed: a soft material that responded electrically. At that point, the sensing side was in a good place.

Then came the next step. With support from Illinois-Indiana Sea Grant, we started testing these materials in environments influenced by water. Not because the goal was only to apply this in water, but because water is a great way to stress-test a system. It introduces constant motion, repeated loading, and environmental exposure all at once.

And once again, something didn’t quite behave the way we expected.

WPU works very well as a sensing material, but over time, it is sensitive to moisture, which can affect its stability. So instead of trying to fix that directly, we changed the design.

Now, we are using fuse deposition modeling 3D printing to build structures out of TPU foam, a flexible, durable material that is more stable in humid environments. These structures define the shape, provide mechanical support, and can even be designed to float. Inside those structures, I embed the sensing elements.

We use the WPU-based material for piezoresistive sensing, which measures changes in electrical resistance when mechanical stress or strain is applied, and we also incorporate flexible piezoelectric elements that respond to vibration and fast motion. Together, they allow the system to capture both slow and rapid changes.

Instead of relying on one material to do everything, the system becomes a combination of parts that each do their job well.

Right now, I’m not trying to build a final device. I’m trying to understand how these systems behave. How stable is the signal over time? What happens when everything is constantly moving? How does water affect the response? There’s also a bigger question in the background: Can this motion be turned into usable energy?

I’m not claiming that yet, but I am measuring what’s there, testing simple circuits, and trying to understand what is realistically possible.

What I like most about this project is that it didn’t follow a straight path. Every time something didn’t work, it pushed the design in a different direction. And little by little, it turned into something more interesting, a system where structure, sensing, and response are all combined.

And I’m still figuring out what that system can really do.