Microscopic 3D-Printed Robots Remove Blood Toxins
Researchers have designed 3D-printed robots as “microfish” that swim through the patients’ bloodstream, delivering drugs, pinpointing and removing toxins. The 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.
Nano-engineers at the University of California, San Diego used an innovative 3D printing technology they developed, to manufacture multipurpose fish-shaped 3D-printed robots — 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” micro-robots 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 micro-robots with various locomotion mechanisms, such as micro-jet engines, micro-drillers and micro-rockets.
Most of these 3D-printed robots 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 micro-robots.
COMBINED 3D PRINTING WITH NANOTECH
By combining Chen’s 3D printing technology with Wang’s expertise in micro-robots, the team was able to custom-build microfish that can do more than simply swim around when placed in a solution containing hydrogen peroxide. Nano-engineers 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.
Schematic illustration of the process of functionalising 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.
“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 nano-engineering Ph.D. student in Chen’s research group at the Jacobs School of Engineering at UC San Diego.
TOXIN SCAVENGER NANO ROBOTS
As a proof-of-concept demonstration, the researchers incorporated toxin-neutralising nanoparticles throughout the bodies of the 3D-printed robots. 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 coloured light. The team was able to monitor the detoxification ability of the microfish by the intensity of their red glow.
“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.
“Another exciting possibility we could explore is to encapsulate medicines inside the microfish and use them for directed drug delivery,” said Jinxing Li, the other co-first author of the study and a nano-engineering Ph.D. student in Wang’s research group.
THIS IS HOW IT WORKS
The new microfish fabrication method is based on a rapid, high-resolution 3D printing technology called micro-scale 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 3D-printed robots, 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 digitised, the researchers could easily experiment with different designs for their microfish, including shark and manta ray shapes.
“With our 3D printing technology, we are not limited to just fish shapes. We can rapidly build micro-robots inspired by other biological organisms such as birds,” said Zhu.
The key component of the μCOP technology is a digital micro-mirror array device (DMD) chip, which contains approximately two million micro-mirrors.
Each micro-mirror 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 3D-printed robots 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.