A team of nanoengineers has created a minuscule 3D-printed robotic fish – or microfish – that they hope will one day be used as a drug delivery system in the body. The tiny microbots can propel themselves, be steered using magnets, and even neutralize toxins in a fluid if loaded with the correct nanoparticles.

“We have developed an entirely new method to engineer nature-inspired microscopic swimmers that have complex geometric structures and are smaller than the width of a human hair,” explained Wei Zhu, who co-led the study published in Advanced Materials. “With this method, we can easily integrate different functions inside these tiny robotic swimmers for a broad spectrum of applications.”

The development of the microfish is reliant on using rapid high-resolution 3D printing, which allows the scientists to print out an array containing hundreds of tiny microbots, each of which are just 120 microns long and 30 microns thick – about half the width of a human hair. The use of the 3D printing technology also means that the researchers can easily alter their designs, creating shapes such as minuscule sharks or manta rays.

The researchers from UC San Diego were then able to add nanoparticles into certain regions of the bot, giving different areas separate properties. For example, by loading their tails with platinum nanoparticles that react with hydrogen peroxide, the fish can propel themselves through their environment. The nanoengineers could then add magnetic iron oxide to the heads of the fish, allowing them to steer the microbots with magnets as they move themselves through the fluid.

But the application of the nanoparticles in the microfish doesn’t stop there. By incorporating toxin-neutralizing nanoparticles through the entire body of the fish, the researchers could design them to detoxify a fluid. To demonstrate this, they added polydiacetylene nanoparticles, which bind to toxins found in bee venom. When added to a solution containing the toxins, the microfish became fluorescent and turned an increasingly intense red as they bound more and more of the toxin molecules.

“The neat thing about this experiment is that it shows how the microfish can doubly serve as detoxification systems and as toxin sensors,” said Zhu. But that’s not where the applications of the tiny robofish stop. The researchers envision that they could be used as directed drug delivery systems or in personal therapeutics. “It's my personal hope to further this research to eventually develop surgical microrobots that operate safer and with more precision,” said Jinxing Li, another of the study's authors.