Filling your bloodstream with billions of nanomachines to keep yourself healthy and strong may sound like the stuff of science fiction, but with the recent creation of a robot about the size of a human egg cell, MIT researchers have brought us a step closer to that being a reality. This particular machine consists of a circuit bonded to an insoluble colloid particle. It's only about .1 mm across, making it nearly invisible to the naked eye and giving it the ability to float in the air or be suspended in liquids without causing any ill effects, even in somewhat large numbers. They're also so tiny that they can remain floating or suspended indefinitely because the pull of gravity on them is less forceful than random collisions with other particles in the air or liquid, meaning that they will never sink to the ground or settle the bottom of a body of liquid.
The tiny robots built here aren't capable of much, but they provide a groundwork of sorts for future projects that could be more impressive in scale. They're self-powered by a single photodiode and are capable of reading local data through a variety of miniaturized sensors. That data can be stored in onboard flash memory so long as the unit remains powered, and once data collection is complete, the data can be read out with special equipment. The tiny, two-dimensional electronics used in this project are made of next-generation materials such as graphene but are too small to function on their own. The need for a substrate is currently a big factor holding back feature addition, but research into fitting more components onto each circuit is ongoing.
MIT's approach in this area contrasts similar projects in that they are looking to make tiny machines more mobile and more easily able to move about and collect data from different areas, while MIT wants the bots to be propelled by environmental sources of kinetic energy, and instead devote the space and energy needed for motor function to a wider range of sensing and data collection and transmission functions. This approach, in the long run, could lead to extremely small electronic devices on organic substrates that can collect and transmit all sorts of data discretely, and perhaps even bind together using those organic substrates in order to actually perform work. While the logical end of this would seemingly be fictional nanomachines as seen in the likes of Metal Gear Rising: Revengeance and Terminator, that sort of high level of function and fluidity is not possible with current technologies, and is thus a very long way off, if it ends up being feasible at all.