At Virginia Tech’s Nature Inspired Fluids and Interfaces (NIFI) lab, a team of student researchers are studying how jumping water droplets can be used to keep crops healthy, and improve energy efficiency.

 

The NIFI lab is the brainchild of Dr. Jonathan Boreyko, an associate professor in Mechanical Engineering. Boreyko’s research synthesizes environmental and life sciences concepts with his engineering background. A common thread in Boreyko's work is biomimicry. Biomimicry is when natural phenomena are used as inspiration for systems or products that solve human problems. “Why be radically creative and think of completely new things when you can look around at how creative nature already is” says Borekyo.

 

Currently, a dozen Virginia Tech students work in the NIFI lab on a variety of projects. One of these students is Grant Helm, a senior studying Mechanical Engineering. Helm started researching at NIFI earlier this summer. One project that Helm has been working on is using high speed videography to analyze how disease spores spread between barley plants. Helm explains how “when water droplets coalesce on a hydrophobic surface like a plant leaf, they release a little bit of kinetic energy and jump off the surface." If a plant is sick, fungal spores on its leaves can hitch a ride on these jumping water droplets. Once the water droplets clear the “boundary layer” immediately around the leaf, the spores can be blown downwind, quickly spreading to nearby plants.

 

Jumping droplets were first discovered by Boreyko in 2012, who was studying the phenomena in wheat plants. Helm is trying to identify any differences in the behavior of jumping droplets on Barley leaves. Something new that Helm has observed is a "billiard ball" effect where all of the energy created by droplets fusing together is transferred directly into a spore, launching it into the air. All of this research is made possible by the NIFI lab’s Phantom high speed camera, which can capture up to 1 million frames per second. “The imaging is something that I didn’t expect to do in the lab, and it’s been really fun,” says Helm.

 

Another project that Helm is working on at NIFI involves figuring out how to improve the efficiency of heat transfer in boiling processes. Every liquid has a critical heat flux, which is the rate of heating at which a vapor barrier forms between the liquid and the heating element. At that point, the heat is no longer being transferred effectively into the liquid. “You aren’t heating the water anymore, you're just melting the pot,” Helm explains. It’s been established that the best way to improve the efficiency of boiling is to raise the critical heat flux, which can be achieved by shrinking the size of the bubbles in the liquid.

 

What researchers at the NIFI lab are trying to do is get these small bubbles to leave the surface of the liquid prematurely, which would further improve efficiency. What they have found is that when the bubbles are small enough, they begin to act similarly to the jumping water droplets on a leaf. They merge together and jump off the surface, preventing a vapor barrier from forming and allowing for more heat to be transferred to the liquid.

 

A major practical application of this concept is in power generation. Most power plants, conventional and nuclear, use boilers to create steam to spin turbines. Improving the energy efficiency of this process at the source could have significant positive effects, including a reduced carbon footprint to cheaper energy costs for consumers.

 

Boreyko and his team are also interested in applying these same principles to cooling processes. Data centers are a particularly compelling use case because they are putting an increasingly significant strain on the power grid. “Currently we are just blowing chilled air across these entire facilities, so it’s not very efficient,” says Boreyko. As condensation forms on cooling equipment, it becomes less efficient. If this equipment was coated in a hydrophobic material those droplets could jump off the surface and evaporate, allowing for more heat to be absorbed.

 

The NIFI lab not only offers students the opportunity to work hands-on on a variety of projects, it also fulfills a longtime personal goal of Boreyko. “I didn’t do any research as an undergraduate, I didn’t have those experiential learning moments,” Boreyko explains. Running the NIFI lab allows Boreyko to provide the experience that he wishes he had gotten as a student. “I’ve published over 80 papers now, so that's not necessarily going to blow my socks off anymore. But it never gets old seeing a student run up to my office to show me something they just discovered.” says Borekyo. Grant Helm says that “looking at things experimentally is a really great way to learn about how things work in the real world.” Helm is looking forward to the next breakthrough moment in the lab. “That’s going to be really really satisfying.” For more information on the NIFI lab at Virginia Tech, visit their website.