'Microfish' robots for controlled drug delivery
Nanoengineers from the University of California are using 3D-printing to build fish shaped microrobots, chemically powered by hydrogen peroxide which are magnetically controlled to 'swim' through a patient's bloodstream to deliver drugs, pinpointing and removing toxins. The 3D-printing method is called, 'microscale continuous optical printing', which creates hundreds of fish-shaped microbots. The printer is capable of creating custom shapes and by adding nanoparticles, the microbots can perform multiple different functions.
Nanoengineers at the University of California, San Diego used 3-D printing to build fish-shaped microrobots. The so-called microfish can swim in liquids, are chemically powered by hydrogen peroxide and are magnetically controlled.

The scientists said the synthetic microfish will inspire a new generation of ‘smart’ microrobots capable of detoxification, sensing their environment, and directing drug delivery.

Making the fish​

The resarchers manufactured the fish with complex mechanisms for movement, including microjet enginers, microdrillers and microrockets, which they say are improvements over previous simpler microbot locomotion methods.

“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,​” they said.

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: Zhu and Li, UC San Diego Jacobs School of Engineering).

The San Diego microfish added functional nanoparticles to parts of the microfish bodies: platinum nanoparticles in the tails, which react with hydrogen peroxide to propel the microfish forward; and iron oxide nanoparticles in the heads, which lets them be steered with magnets.

“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 Wei Zhu, one of the researchers.

Proof-of-concept​

To demonstrate applications of the magnetised microfish, the scientists put toxin-neutralizing nanoparticles into the robots’ bodies (polydiacetylene, which captures the harmful pore-forming toxins in bee venom). In the experiment, the microfish’s “powerful swimming​” in solution “greatly enhanced their ability to clean up toxins​”.

Polydiacetylene nanoparticles become fluorescent and glow red when they bind with toxin molecules, allowing the researchers to easily measure detoxification.

“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.

Fellow researcher Jinxing Li added, “Another exciting possibility we could explore is to encapsulate medicines inside the microfish and use them for directed drug delivery.​”

3-D printing technology is not limited to fish shapes and other nature-inspired microrobots, like micro-birds, are a future possibility, the scientists said.

The team was led by the university’s nanoengineering professors Shaochen Chen – an expert in 3-D printing – and Joseph Wang – who focuses on microrobots.

Source:​ ‘3D-Printed Artificial Microfish’, Advanced Materials​, August 2015, Wei Zhu, Jinxing Li, Yew J. Leong, Isaac Rozen, Xin Qu, Renfeng Dong, Zhiguang Wu, Wei Gao, Peter H. Chung, Joseph Wang, and Shaochen Chen (Department of NanoEngineering at the UC San Diego Jacobs School of Engineering).

DOI:​ 10.1002/adma.201501372​.