Tiny, cell-sized robots may help monitor diseases

MIT scientists have created the smallest robots yet that can sense their environment, store data, and even carry out computational tasks, paving the way for ingestible health monitoring tools.

The devices, which are about the size of a human egg cell, consist of tiny electronic circuits made of two-dimensional materials, piggybacking on minuscule particles called colloids.

Colloids, which insoluble particles or molecules anywhere from a billionth to a millionth of a meter across, are so small they can stay suspended indefinitely in a liquid or even in air.

By coupling these tiny objects to complex circuitry, researchers hope to lay the groundwork for devices that could be dispersed to carry out diagnostic journeys through anything from the human digestive system to oil and gas pipelines, or perhaps to waft through air to measure compounds inside a chemical processor or refinery.

"We wanted to figure out methods to graft complete, intact electronic circuits onto colloidal particles," said Michael Strano, a professor at Massachusetts Institute of Technology (MIT) in the US.

"Colloids can access environments and travel in ways that other materials can't," Strano said.

Dust particles, for example, can float indefinitely in the air because they are small enough that the random motions imparted by colliding air molecules are stronger than the pull of gravity.

Similarly, colloids suspended in liquid will never settle out.

Strano said that while other groups have worked on the creation of similarly tiny robotic devices, their emphasis has been on developing ways to control movement.

However, making such devices more functional is more important than making them mobile, researchers said.

The tiny robots, published in the Nature Nanotechnology, are self-powered, requiring no external power source or even internal batteries. A simple photodiode provides the trickle of electricity that the tiny robots' circuits require to power their computation and memory circuits.

That is enough to let them sense information about their environment, store those data in their memory, and then later have the data read out after accomplishing their mission.

Such devices could ultimately be a boon for the oil and gas industry, Strano said. Currently, the main way of checking for leaks or other issues in pipelines is to have a crew physically drive along the pipe and inspect it with expensive instruments.

The new devices could be inserted into one end of the pipeline, carried along with the flow, and then removed at the other end, providing a record of the conditions they encountered along the way, including the presence of contaminants that could indicate the location of problem areas.

Such particles could also potentially be used for diagnostic purposes in the body, for example to pass through the digestive tract searching for signs of inflammation or other disease indicators, researchers said.