Not all autonomous robots need artificial intelligence to power them. At the molecular level, nanobots can do pretty impressive things without lines of code dictating their moves. They do our bidding because the physical laws of their environment force them to do so.
By exploiting such quirks of nature, scientists have now built nanobots that can repair broken circuits that are too small for a human eye to see. Such tiny repairs could help modern electronics have a longer shelf life, but these proof-of-concept, autonomous nanobots have bigger potential. They could one day soon be used for self-healing materials and delivering drugs inside the human body.
To build them, Joseph Wang of the University of California at San Diego and Anna Balazs of the University of Pittsburgh took inspiration from nature. When you cut yourself, the platelets in your blood sense the wound and start aggregating to start the healing process. They wanted to create tiny robots that could do something similar.
So they started with Janus particles made of gold and platinum. These spherical nanobots (or “nanomotors” as the researchers call them) are thousands of times smaller than a pinhead and have two surfaces with distinct properties. This choice was critical to power the nanobots to act as Wang and Balazs wanted them to.
When these Janus particles are poured in a solution containing hydrogen peroxide, the platinum half of the particles reacts with the chemical, causing oxygen to be released. The reaction is so rapid that the released oxygen propels nanobots like a jet would be propelled by rocket fuel.
To test whether Janus particles in the chemical mixture would do their bidding, Wang and Balazs created a simple circuit that connected a battery to an LED light. Then they broke the circuit by making a scratch that was less than one-tenth the width of a human hair. When Janus particles and hydrogen peroxide solution was poured onto the circuit, the nanobots got into action.
After about 30 minutes, they removed the solution and turned the battery on to find that the LED light was working again. In another broken circuit, simply adding the Janus particles without hydrogen peroxide solution did not lead to repair. The results of the study have been published in the journal Nano Letters.
A computer model of the experiment showed that particles moving randomly could not have repaired the circuit. Instead, Wang and Balazs think that the scratch created differences in the surface energies that the gold-side of the nanobots could “sense.” These energy differences (created by changes in the molecular forces) drove the nanobots to the broken circuit and the geometry of the gap trapped them there.
Next, they are hoping to find new applications for these chemical-powered nanobots. To do that, instead of programming lines of code, they need to find environments where physical laws would dictate the movement of the nanobots.