How cell-sized robots can be used for sensing and interfacing with electronics

By Warren Miller, contributing writer

We’ve all gotten used to technology getting smaller and smaller over the years, even to the point where we all carry computers the size of a stack of index cards around with us in our pockets all day long. But are we ready for robots no larger than a single human cell? It sounds like the stuff of science fiction, but a group of physicists at Cornell University have developed a tiny “muscle” that they say can perform some basic physical functions — like a larger industrial robot might — on a cellular level.

The microscopically small machine can move or change shape in reaction to changes in its environment, such as elevations or dips in temperature. The mechanism itself employs a motor called a bimorph, a conjunction of two different materials that expand at different rates when exposed to heat, an electrical voltage or some kind of chemical reaction. The bimorph, in this case, is composed of graphene and glass — by laying flat panels of materials that are too rigid to bend over the bimorph itself, the researchers found that they could create solid structures in the form of simple shapes like triangles or cubes. “We are trying to build what you might call an ‘exoskeleton’ for electronics,” said Paul McEuen, the John A. Newman Professor of Physical Science and director of the Kavli Institute at Cornell for Nanoscale Science. “Right now, you can make little computer chips that do a lot of information-processing, but they don’t know how to move or cause something to bend.”

A tiny “muscle” can perform basic physical functions on a cellular level. Image source: Cornell.

The bimorph itself is built by applying thin layers (no thicker than an atom) of silicon dioxide onto an aluminum surface and then stacking an equally thin layer of graphene on top, resulting in the thinnest bimorph ever constructed. The team has created several different machines with this bimorph, ranging in size from “three times larger than a red blood cell” to “three times smaller than a large neutron.”

It’s important to note that, although microscopic structures like the ones the Cornell team can create with the bimorph have been built before via different methods, these new machines have the benefit of being compatible with semiconductor manufacturing. “If you want to build this electronics exoskeleton, you need it to be able to produce enough force to carry the electronics,” said postdoctoral researcher Marc Miskin. New applications for this technology are also being explored. “Right now, there are no ‘muscles’ for small-scale machines,” asserts McEuen, “so we’re building the small-scale muscles.”

Mixing electronics and nano-scale motors should find many more applications than having your cellphone run over to you when you call. Think of the variety of very small-scale electronics devices that could do everything from checking the integrity of oil pipelines from inside the pipeline or even smaller robots that could hunt out cancer cells and destroy them from inside the human body. If these devices can be powered via heat differentials, blood pressure, or the turbulence in a fluid flow, they could last for years doing their jobs almost invisibly.