Promising Medical Microrobots Could One Day Treat Bladder Disease

A team of engineers has designed a new class of tiny, self-propelled robots that can zip through liquid at incredible speeds and may one day even deliver prescription drugs to hard-to-reach places inside the human body.

The group’s microrobots used for the study are really small. Each one measures only 20 micrometers wide, several times smaller than the width of a human hair. They’re also really fast, capable of traveling at speeds of about 3 millimeters per second, or roughly 9,000 times their own length per minute. That’s many times faster than a cheetah in relative terms.

“Imagine if microrobots could perform certain tasks in the body, such as non-invasive surgeries,” said Jin Lee, lead author of the study. “Instead of cutting into the patient, we can simply introduce the robots to the body through a pill or an injection, and they would perform the procedure themselves.”

In the new study, the group deployed fleets of these machines to transport doses of dexamethasone, to the bladders of lab mice. The results suggest that microrobots may be a useful tool for treating bladder diseases and other illnesses in people.

The team makes its microrobots out of materials called biocompatible polymers using a technology similar to 3D printing. The machines look a bit like small rockets and come complete with three tiny fins. They also include a little something extra: Each of the robots carries a small bubble of trapped air, similar to what happens when you dunk a glass upside-down in water. If you expose the machines to an acoustic field, like the kind used in ultrasound, the bubbles will begin to vibrate wildly, pushing water away and shooting the robots forward.

To take their microrobots for a test drive, the researchers set their sights on a common problem for humans: bladder disease.

In laboratory experiments, the researchers fabricated schools of microrobots encapsulating high concentrations of dexamethasone. They then introduced thousands of those bots into the bladders of lab mice. The result was: The microrobots dispersed through the organs before sticking onto the bladder walls, which would likely make them difficult to pee out.

Once there, the machines slowly released their dexamethasone over the course of about two days. Such a steady flow of medicine could allow patients to receive more drugs over a longer span of time, Lee said, improving outcomes for patients.

He added that the team has a lot of work to do before microrobots can travel through real human bodies. “If we can make these particles work in the bladder,” Lee said, “then we can achieve a more sustained drug release, and maybe patients wouldn’t have to come into the clinic as often.”


Jin Gyun Lee, Ritu R. Raj, Cooper P. Thome, Nicole B. Day, Payton Martinez, Nick Bottenus, Ankur Gupta, C. Wyatt Shields. Bubble‐Based Microrobots with Rapid Circular Motions for Epithelial Pinning and Drug Delivery. Small, 2023; DOI: 10.1002/smll.202300409

University of Colorado at Boulder. “Medical ‘microrobots’ could one day treat bladder disease, other human illnesses.” ScienceDaily. ScienceDaily, 24 May 2023. <>.

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Photo by Lucas Vasques