Many of the recent breakthroughs, in medical science, have been the result of the implementation of nanotechnology principles. These include the use of nanodiamonds for targeted drug delivery and therapeutics; gold nanoparticles for the detection of breast cancer as well as specially-designed nano drones that help prevent heart attacks by repairing arterial inflammation. Using an innovative 3D printing technique, scientists at the University of California, San Diego, have developed tiny fish-shaped robots, known as “microfish”, that can perform a variety of tasks, such as directed drug delivery and detoxification.

Led by Shaochen Chen and Joseph Wang of UCSD’s Department of Nanoengineering, the research was recently published in the Advanced Materials journal. Unlike similar technologies used in microrockets, microjet engines and micro-drillers, the tiny robotic fish boasts a highly-complex design, which in turn allows it to perform an array of incredibly sophisticated tasks. Its ability to swim inside the human body is actually controlled chemically by hydrogen peroxide and also, magnetically by means of iron oxide nanoparticles. Speaking about the project, Wei Zhu, a Phd student at the Jacobs School of Engineering and the study’s co-author, said:

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.

To build the microfish, the team relies on advanced, high-resolution 3D printing, developed by the researchers at Chen’s lab. Dubbed as microscale continuous optical printing (or μCOP), the technology is known for its speed, accuracy and flexibility. Central to such a technique is a highly-specialized optical chip, called digital micromirror device (DMD), containing over 2 million micromirrors. Each of these minute mirrors is programmed to project UV light (in different shapes and patterns) onto a photosensitive material, which in turn solidifies when exposed to UV rays. Zhu added:

With our 3D printing technology, we are not limited to just fish shapes. We can rapidly build microrobots inspired by other biological organisms such as birds

This approach allows the scientists to fabricate several hundred microfish, measuring around 120 microns in length and nearly 30 microns in thickness, within a matter of seconds. Furthermore, the robot’s layered design enables the researchers to incorporate multiple sets of functional nanoparticles, into specific sections of the design. Jinxing Li, a Phd student in Wang’s team, explained:

This method has made it easier for us to test different designs for these microrobots and to test different nanoparticles to insert new functional elements into these tiny structures. It’s my personal hope to further this research to eventually develop surgical microrobots that operate safer and with more precision.

In order to make them swim around in liquids, the team installs platinum nanoparticles onto the tails of the 3D-printed microfish. When submerged into a solution containing hydrogen peroxide, the particles undergo chemical reaction, thereby propelling the fish forward. Iron oxide particles, placed in the bot’s head, help steer the fish magnetically. To demonstrate the efficacy of the technology in removing harmful substances from the human body, the scientists plant toxin-neutralizing polydiacetylene (PDA) nanoparticles into the body of the microfish.

In the presence of toxins, such as the kind found in bee venom, the PDA nanoparticles turn fluorescent and emanate bright red light. By monitoring the intensity of the red glow, the researchers are able to estimate the toxicity level of the bot’s surrounding. According to the scientists, the microfish could one day be used to deliver drugs to the remotest cells of the human body as well as perform delicate microsurgeries, team added:

The neat thing about this experiment is that it 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.

Researchers Wei Zhu and Jinxing Li at UCSD’s Jacobs School of Engineering

Source: UCSD News / Advanced Materials