3D-printed microscopic fish could be forerunners to smart "microbots"

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As PDA nanoparticles in the microfish bodies bind with toxins, the microfish turn fluorescent red(Credit: W. Zhu and J. Li, UC San Diego Jacobs School of Engineering)

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Tiny 3D-printed robotic fish smaller than the width of a human hair may one day deliver drugs to specific places in our bodies and sense and remove toxins, thanks to research at the University of California, San Diego. The so-called microfish are self-propelled, magnetically steered, and powered by hydrogen peroxide nanoparticles. And they might be just the first chip off the block for a future filled with "smart" microbots inspired by other biological organisms such as birds, each with its own specialized functionality.

These microfish are not the first micro-sized robots, though. Others include the robotic micro-scallop, which got its name from its scallop-like propulsion system; laser-powered air-bubble microbots; and magnetically-levitating microbots, which as the name suggests hover in the air under control of a magnetic field.

The microfish are different in that they are both simpler to create and more sophisticated in what they can do. They are fabricated using a high-resolution 3D printing technology called microscale continuous optical printing. This process allows researchers to print hundreds of 120-microns-long, 30-microns-thick microfish at once. And they can quickly change the design to experiment with shark, manta ray, and even bird shapes by tweaking a few things in a custom-designed computer-aided design (CAD) program.

Each microfish contains platinum nanoparticles in its tail and iron oxide nanoparticles in its head. When placed in a solution containing hydrogen peroxide, the tail nanoparticles undergo a chemical reaction that propels the microfish forward. The nanoparticles in the head allow for the microfish to be steered with magnets.

The researchers ran a proof-of-concept experiment to see how the microfish perform with detoxification – one of many possible applications envisioned for them. They scattered toxin-neutralizing polydiacetylene nanoparticles throughout the microfish bodies and put them into a solution filled with toxins. The microfish turned fluorescent and glowed an increasingly-intense shade of red as their toxin-neutralizing nanoparticles chemically bound with the toxin molecules.

The researchers took this to mean that the microfish can serve the dual function of a detoxification system and toxin sensor. They also believe the microfish could be used for directed drug delivery, personal therapeutics, environmental conservation, and many other applications. And co-first author of the study Jinxing Li hopes to one day come up with a design that could be used to develop surgical microbots that make operations safer and more precise.

A paper describing the study was published in the journal Advanced Materials.

Source: UC San Diego

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