Super-fast Insect Urination Powered by the Physics of Superpropulsion

Assistant Professor Saad Bhamla was in his backyard when he noticed something he had never seen before: an insect urinating.

Although nearly impossible to see, the insect formed an almost perfectly round droplet on its tail and then launched it away so quickly that it seemed to disappear. The tiny insect relieved itself repeatedly for hours.

It’s generally taken for granted that what goes in must come out, so when it comes to fluid dynamics in animals, the research is largely focused on feeding rather than excretion.

But Bhamla had a hunch that what he saw wasn’t trivial.

“Little is known about the fluid dynamics of excretion, despite its impact on the morphology, energetics, and behavior of animals,” he said.

sharpshooters – tiny pests notorious for spreading disease in crops –excrete the way they do.

By using computational fluid dynamics and biophysical experiments, the researchers studied the fluidic, energetic, and biomechanical principles of excretion, revealing how an insect smaller than the tip of a pinky finger performs a feat of physics and bioengineering – superpropulsion.

Their research, published in Nature Communications, is the first observation and explanation of this phenomenon in a biological system.

“We wanted to see if this tiny insect had come up with any clever engineering or physics innovations in order to pee this way.” - Saad Bhamla (left, with Elio Chalita)

He and Bioengineering PhD student Elio Chalita investigated how and why glassy-winged

Studying how sharpshooters use superpropulsion can also provide insights into how to design systems that overcome adhesion and viscosity with lower energy. One example is low-power waterejection wearable electronics, such as a smart watch that uses speaker vibrations to repel water from the device.

Georgia Tech Engineers Develop Carbon Membranes Enabling Efficient Removal and Concentration of Organic Molecules from Water

The need to remove organic contaminants from surface waters continues to grow due to an increasing influx from industrial, municipal, and agricultural sources. But these contaminants are challenging to remove outside of thermally driven separation processes, such as distilling or drying, which consume significant amounts of energy.

However, researchers in ChBE@ GT have developed rigid, carbon membranes that effectively remove and concentrate small organic molecules (such as solvents) from water, based on the affinity between the organic species and carbon membrane.

Published in Proceedings of the National Academy of Sciences, this discovery challenges conventional understanding, said Professor Ryan Lively. That’s because the new carbon membranes enable the permeation, rather than rejection, of organic molecules from aqueous mixtures, leading to their higher concentration in the membrane permeate compared to the membrane feed.

Traditionally, most membranes are designed to selectively permeate clean water while creating a highly concentrated organic waste stream that requires additional treatment.

However, the unique behavior of these carbon membranes derived from a polymer of intrinsic microporosity developed by the Georgia Tech team has the unexpected ability to allow the enhanced passage of organic molecules relative to that of water molecules.

“This observation was unexpected and puzzling for several months, and we were highly skeptical of these findings.” - lead author Haley White (ChBE PhD 2022).

Scrubbing Carbon Directly from the Air:

New Direct Air Capture Center Leveraging Georgia Tech’s Leadership in Burgeoning Field

In 2015, nearly 200 countries agreed: they would reduce their emissions of carbon dioxide and other greenhouse gases to limit warming of the earth’s atmosphere to well below 2 degrees Celsius.

The Paris Agreement actually aims for 1.5 degrees above pre-industrial levels to avoid potential catastrophic changes to our climate. But it’s become increasingly clear to climate scientists and policymakers that just reducing emissions is not enough.

“We now know that we probably should have stopped putting massive amounts of CO₂ in the air 10, 20, 30 years ago to prevent the climate from getting above 2 degrees C,” said Professor Chris Jones.

“Now we’ve waited so long to reduce our emissions that we need to develop technologies that are referred to as negative emissions technologies that remove CO₂ from the atmosphere.”

Jones was one of a handful of scientists who co-authored a landmark National Academies report in 2018 that outlined a variety of approaches to negative emissions. Agricultural practices and forest management are options — essentially using nature’s ability to grab carbon dioxide out of the air and lock it away in plants and soil. But Jones said we’ll need quicker and more direct approaches.

“We could plant billions of trees to do this, but there’s not enough available land. And the trees don’t grow fast enough for us to do this quickly enough to slow global warming at the rate required.” - Chris Jones

That’s where direct air capture comes in: It’s a chemical engineering way of designing a process that takes CO₂ out of the air.

Direct air capture is a bit like a massive household air purifier — but for the globe. Systems would pull air across specially designed filter materials with molecules that grab CO₂. When the filters are saturated, they’re cleaned, and the carbon dioxide is pumped underground for storage in the very places we’ve extracted oil and natural gas over the decades.

It’s a technology proposed only in 1999, with companies launched in 2008, and it’s now quickly becoming a reality, according to Professor Matthew Realff.

“It’s definitely a technology that is moving past the lab; it’s in the pilot scale/deployment phase as an initial technology. By 2030, we should see deployment of what I would call the first commercial-scale facilities in different places in the United States — systems that can remove a million tons of CO₂ a year.”

“If you’re going to make a difference, to be honest, it really needs to be at about 1,000 times that scale, a gigaton scale of direct air capture,” Realff continued. “Some people would argue that we might need even more than that two to three decades from now, depending on how our emissions reduction efforts go.”

Realff and Jones are working at different ends of the direct air capture spectrum — the systems and molecular levels — to develop the technology. In between is ChBE Professor Ryan Lively, who works on materials, devices, and processes. Now they’re recruiting more of their Georgia Tech colleagues to the cause with a newly established Direct Air Capture Center (DirACC) within Tech’s Strategic Energy Institute.

Leveraging Longstanding Leadership

“As an institution, Georgia Tech has essentially been involved since the direct air capture field’s infancy,” Jones said.

Jones has led collaborations since 2008 with one of the original startup companies in the field, Global Thermostat. Lively leads an Energy Frontier Research Center that’s working on how materials for cleanenergy technology evolve and degrade. One of the focus areas is direct air capture.

Alongside the 2018 National Academies report, Congress intro- duced a federal tax credit for removing carbon dioxide from the air. Lawmakers more than tripled those incentives to $180 per ton in the 2022 Inflation Reduction Act. Jones said that got people’s attention.

“Since 2018, we’ve had billions of dollars of legislation for direct air capture technology research and development. That trend is why we are launching the Direct Air Capture Center now: We really want to communicate to the outside that we are a hub in this space.” - Chris Jones

Lively said DirACC will fill a need nationally to act as a convener of researchers, industry, funders, and other stakeholders. It is one of a few centers in the nation focused on direct air capture and the first such effort to encompass the complete supply chain of capture and sequestration of CO₂ from the air.

Location Matters

Jones works at the first step of the carbon-capture process: the molecules that link with CO₂ to pull it out of the air. One of the areas he’s become most interested in is customizing different materials for different locations and climates.

“A molecule or a material that we studied five years ago maybe failed operating at 80 degrees Fahrenheit. That would not work in Atlanta or in Florida, but maybe it works really well if we go to 50 degrees F or 20 degrees F, and we can deploy it in Montana,” Jones said. “We’re starting to think more about whether we might have advantaged materials or advantaged processes in particular locations.”

In a future where direct air capture is widely deployed — say, 20 years from now — Jones said there could be a dozen different solutions customized to different locations around the globe.

Another frontier is engineering carbon capture materials that will last long enough to be economically practical, Lively said.

The center’s researchers developed coated carbon fibers housed in a canister, a design inspired by Ryan Lively’s encounter with an old pneumatic tube in a bank drive-through.

Using ambient wind flow to draw air across the fibers, the system captures carbon dioxide with sufficient purity for underground sequestration and eliminates many of the substantial upfront costs of building a typical DAC system.

When Jones creates molecules that grab carbon dioxide out of the air, Lively incorporates them into fibers that can be bundled together or even woven into fabric. Those fibers seem to be durable, but the question is whether the delicate chemistry of the molecules repeatedly capturing and then releasing the CO₂ can hold up. The DOE-funded center Lively leads is working in part to better understand how these materials evolve and degrade.

“One of the key cost drivers is, how long can you make these things last?” Lively said.

Creating fibers for use in a canister, filter, or other device has become a fairly mature technology, Lively said, so the team is working now to move some of their materials into the commercial market. He’s also experimenting with 3D printing approaches that can create more complex structures with the materials.

Another emerging idea would pair direct air capture systems with natural gas combined-cycle power plants. These plants use gas to turn a turbine and generate electricity. The waste heat from that process is then used to create steam that turns another turbine and generates more power.

Realff, Jones, and Lively have partnered with ChBE’s Fani Boukouvala and Joe Scott on a project to instead use that steam to do conventional post-combustion carbon capture and to power a direct air capture system.

“With the combination of those two systems, we can get natural gas combined-cycle plants that can operate and be net negative in their carbon dioxide,” Realff said.

In fact, he said, the reduction in carbon from such a system would be enough to wipe out the carbon emissions of another power plant operating at full capacity.

No Time to Waste

Those kinds of advances will be critical to making direct air capture economical enough to have impact, the researchers said.

Jones called it a generational challenge akin to NASA’s failure-isnot-an-option mantra during the 1960s moon missions.

“The level of funding and interest is pretty enormous, but the challenge, unfortunately, might be even more enormous than the interest. The longer we wait, the bigger the challenge.” - Ryan Lively