August 26, 2015

These Microscopic Fish are 3D-Printed to do More Than Swim

3D-printed microfish contain functional nanoparticles that enable them to be
self-propelled, chemically powered and magnetically steered.
The microfish are also capable of removing and sensing toxins.
Image credit: J. Warner, UC San Diego Jacobs School of Engineering.

Researchers demonstrate a novel method to build microscopic robots with complex shapes and functionalities

(August 26, 2015)  Nanoengineers at the University of California, San Diego used an innovative 3D printing technology they developed to manufacture multipurpose fish-shaped microrobots — called microfish — that swim around efficiently in liquids, are chemically powered by hydrogen peroxide and magnetically controlled. These proof-of-concept synthetic microfish will inspire a new generation of “smart” microrobots that have diverse capabilities such as detoxification, sensing and directed drug delivery, researchers said.

The technique used to fabricate the microfish provides numerous improvements over other methods traditionally employed to create microrobots with various locomotion mechanisms, such as microjet engines, microdrillers and microrockets. Most of these microrobots are incapable of performing more sophisticated tasks because they feature simple designs — such as spherical or cylindrical structures — and are made of homogeneous inorganic materials. In this new study, researchers demonstrated a simple way to create more complex microrobots.

Schematic illustration of the process of functionalizing the microfish.
Platinum nanoparticles are first loaded into the tail of the fish for
propulsion via reaction with hydrogen peroxide. Next, iron oxide nanoparticles
are loaded into the head of the fish for magnetic control.
Image credit: W. Zhu and J. Li, UC San Diego Jacobs School of Engineering.

The research, led by Professors Shaochen Chen and Joseph Wang of the NanoEngineering Department at the UC San Diego, was published in the Aug. 12 issue of the journal Advanced Materials.

By combining Chen’s 3D printing technology with Wang’s expertise in microrobots, the team was able to custom-build microfish that can do more than simply swim around when placed in a solution containing hydrogen peroxide. Nanoengineers were able to easily add functional nanoparticles into certain parts of the microfish bodies. They installed platinum nanoparticles in the tails, which react with hydrogen peroxide to propel the microfish forward, and magnetic iron oxide nanoparticles in the heads, which allowed them to be steered with magnets.

Fluorescent image demonstrating the detoxification capability of the
microfish containing PDA nanoparticles.
Image credit: W. Zhu and J. Li, UC San Diego Jacobs School of Engineering.

“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. With this method, we can easily integrate different functions inside these tiny robotic swimmers for a broad spectrum of applications,” said the co-first author Wei Zhu, a nanoengineering Ph.D. student in Chen’s research group at the Jacobs School of Engineering at UC San Diego.

As a proof-of-concept demonstration, the researchers incorporated toxin-neutralizing nanoparticles throughout the bodies of the microfish. Specifically, the researchers mixed in polydiacetylene (PDA) nanoparticles, which capture harmful pore-forming toxins such as the ones found in bee venom. The researchers noted that the powerful swimming of the microfish in solution greatly enhanced their ability to clean up toxins. When the PDA nanoparticles bind with toxin molecules, they become fluorescent and emit red-colored light. The team was able to monitor the detoxification ability of the microfish by the intensity of their red glow.

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