Researchers developed a multipurpose fish-shaped microrobots — called microfish — that swim around efficiently in liquids, are chemically powered by hydrogen peroxide and magnetically controlled.
They used an innovative 3D printing technology to develop this microrobots.
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.
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.
The researchers published their research in the Aug. 12 issue of the journal Advanced Materials. In this new study, researchers demonstrated a simple way to create more complex microrobots.
They have combined 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.
“Nature-inspired microscopic swimmers are smaller than the width of a human hair. We can easily integrate different functions inside these tiny robotic swimmers for a broad spectrum of applications.”
Microfish are almost 120 microns long and 30 microns thick.
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.
“This experiment shows how the microfish can doubly serve as detoxification systems and as toxin sensors.”
“Another exciting possibility we could explore is to encapsulate medicines inside the microfish and use them for directed drug delivery.”
The new microfish fabrication method is based on a rapid, high-resolution 3D printing technology called microscale continuous optical printing (μCOP), which was developed in Chen’s lab. Some of the benefits of the μCOP technology are speed, scalability, precision and flexibility.
Within seconds, the researchers can print an array containing hundreds of microfish, each measuring 120 microns long and 30 microns thick. This process also does not require the use of harsh chemicals. Because the μCOP technology is digitized, the researchers could easily experiment with different designs for their microfish, including shark and manta ray shapes.
The key component of the μCOP technology is a digital micromirror array device (DMD) chip, which contains approximately two million micromirrors. Each micromirror is individually controlled to project UV light in the desired pattern (in this case, a fish shape) onto a photosensitive material, which solidifies upon exposure to UV light.
The microfish are built using a photosensitive material and are constructed one layer at a time, allowing each set of functional nanoparticles to be “printed” into specific parts of the fish bodies.
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