Fish Could Soon Be Swimming Inside Us;

Researchers at the University of California, San Diego, have built tiny fishlike robots that could eventually perform a variety of important tasks, from delivering a highly targeted drug payload inside a human body to detecting or even removing toxins from a liquid environment.
The scientists created the self-powered artificial fish using an innovative 3-D printing technology. Conventional 3-D printing uses a nozzle to deposit succeeding layers of material, but the San Diego team relied instead on an array of 2 million tiny mirrors that project ultraviolet light in the desired pattern onto a photosensitive gel. This material, commonly used in medical applications, was solidified into a fish shape by exposure to the light.
The technique is fast, precise and makes it possible to endow the robot-fish with their special powers. To demonstrate that their technique permits multiple functions to be built into their creations, the scientist implanted platinum particles in the creatures' tails, toxin-neutralizing nanoparticles in their bodies and iron-oxide particles in the heads.
The resulting robots, roughly the thickness of a human hair, were then released into a container of hydrogen-peroxide solution.
The tail platinum reacted with the solution to produce bubbles, which in turn propelled the robotic fish forward. They could be steered using a magnet, which attracted the particles in their heads. And they soaked up toxins in the container, even glowing red as they did so--a feature enabled by the scientists' specific choice of nanoparticles for the fish bodies. In effect, these fish acted as both toxin sensors and detoxification devices.
The researchers note that the fish were much more effective at soaking up toxins while swimming than when they were still. They also observed that conventional fishlike shapes enabled the robots to swim much better than the manta shape the scientists had also tried.
Shaochen Chen, one of the scientists, said that he and his colleagues had yet to determine the optimal shape or whether it might help to give the robots tiny scales. For now, they are using fish that look roughly like tiny sharks.
These sharks might someday save lives. In previous research, Joseph Wang, one of the scientists involved in the latest work with Dr. Chen, was part of a team that created self-propelled micromotors that succeeded in delivering a cargo of gold nanoparticles into the stomach tissue of mice. Propelled by gastric acid, the tiny medical machines had enough power to penetrate the thick mucus of the stomach lining, embedding themselves until they dissolved.
Those micromotors were relatively simple tubes. The new micro-fish offer scientists the possibility of greater control and the ability to integrate more functions.
Dr. Chen says that, using the 3-D nanoprinting technology that he and his colleagues have developed, their robotic fish can be made 100 times smaller. That could be handy for navigating even tiny capillaries--if the scientists can surmount the problems of going even smaller.