We've been hearing a lot lately about the possibility of treating medical conditions using nanobots - tiny robots that would be injected into a patient's bloodstream, where they would proceed to travel to their targets, not unlike the microscopic submarine in the movie Fantastic Voyage ... except nanobots wouldn't be crewed by tiny shrunken-down humans. One challenge that still needs to be met, however, is figuring out a way of propelling the devices. Well, we may now be closer to a solution. Yesterday, development of a new type of nanoscale artificial muscle was announced, which works like the muscles in an elephant's trunk. These could conceivably be used in nanobots, to whip them along using a rotating flagellum - a tiny sperm-like tail, in other words.
At the heart of the artificial muscle is a strand of tough, flexible yarn made from carbon nanotubes that have been twisted together. It is immersed in liquid electrolytes. When voltage is applied, the yarn draws in electrolytes, causing it to increase in volume. This in turn causes it to untwist itself, rotating at up to 600 revolutions per minute as it does so. If the voltage is changed, the yarn then proceeds to discharge the electrolytes. In doing so, it is able to twist itself back up, rotating in the opposite direction.
In a nanobot equipped with batteries and an electrical circuit, the back-and-forth spinning of such a yarn motor attached to a flagellum could cause the tail to wiggle in circles, pushing the nanobot through its liquid environment. The yarns are reportedly simple and inexpensive to make, and can be created in a variety of lengths.
Elephant trunks and octopus tentacles work using a similar principle, in that they incorporate helically wound muscle fibers that rotate in either direction to move the appendage.
The video below illustrates how one of the artificial muscles could work in a nanobot.