How insects urinate may shape the future of technology

By Stephen Beech via SWNS

The unique way a noisy insect takes a leak could inspire better robots.

While most small insects and mammals urinate in droplets, cicadas pee in jets.

Researcher at Georgia Institute of Technology have been taking a close-up look at the way cicadas relieve themselves.

They say their findings, published in the journal Proceedings of the National Academy of Sciences, could be used to create better robots - and small nozzles.

Rather than sprinkling droplets, cicadas emit jets of urine from their small frames.

For years, Georgia Tech researchers have wanted to understand the cicada’s unique urination.

Dr. Saad Bhamla, an Assistant Professor in the School of Chemical and Biochemical Engineering, and his team hoped for a chance to study a cicada’s fluid excretion.

However, while cicadas are easily heard, they hide in trees, making them hard to observe.

Dr. Bhamla’s team had only watched the process on YouTube until, while doing field work in Peru, they saw several cicadas in a tree, peeing.

He explained that the moment of observation was enough to disprove two main insect pee paradigms.

First, cicadas eat xylem sap, and most xylem feeders only pee in droplets because it uses less energy to excrete the sap.

But cicadas are such "voracious" eaters that individually flicking away each drop of pee would be too taxing and would not extract enough nutrients from the sap.

Dr. Elio Challita, now a postdoctoral researcher at Harvard University, said: “The assumption was that if an insect transitions from droplet formation into a jet, it will require more energy because the insect would have to inject more speed."

He said smaller animals are expected to pee in droplets because their orifice is too tiny to emit anything thicker.

Because of cicadas’ larger size - with wingspans that can rival a small hummingbird’s - they use less energy to expel pee in jets.

Dr. Challita said: “Previously, it was understood that if a small animal wants to eject jets of water, then this becomes a bit challenging, because the animal expends more energy to force the fluid’s exit at a higher speed.

"This is due to surface tension and viscous forces. But a larger animal can rely on gravity and inertial forces to pee,”

He said the cicadas’ ability to jet water offered the researchers a new understanding of how fluid dynamics impacts the tiny insects - and even large mammals.

The research group has been studying fluid ejection across species of all shapes and sizes for years.

Their findings show diverse functions - including excretion, venom spraying, prey hunting and spore dispersal - highlighting potential applications in soft robotics, additive manufacturing and even drug delivery.

Dr. Bhamla says cicadas are the smallest animal to create high-speed jets, so they can potentially inform applications in making jets in tiny robots.

He believes the insects could also inform bio-monitoring applications.

Dr. Bhamla said: "Our research has mapped the excretory patterns of animals, spanning eight orders of scale from tiny cicadas to massive elephants.

“We've identified the fundamental constraints and forces that dictate these processes, offering a new lens through which to understand the principles of excretion, a critical function of all living systems."

He added: "This work not only deepens our comprehension of biological functions but also paves the way for unifying the underlying principles that govern life’s essential processes."