Biofluids Fuel Microrockets

Future nanoparticles could rocket drugs to their targets

3 min read
Biofluids Fuel Microrockets
MICROROCKET: A particle made of titanium (green) and aluminum gallium (gray) propels itself by generating a stream of hydrogen bubbles in water.
Image: American Chemical Society

Chemistry teachers with a flair for the dramatic sometimes throw pure sodium into a body of water, causing a reaction that blows the sodium back out of the water and blows their students’ minds. Engineer Wei Gao, at the University of California, San Diego, thinks smaller. He envisions a controlled version of that reaction so small it would fit on one side of a 20-micrometer particle.

For particles that size, ordinary water is as viscous as tar is to us (see the classic lecture “Life at Low Reynolds Number,” [PDF] by Edward Purcell). One way to push through it is to use the fluid itself as fuel. In 2011, Gao and his colleagues dropped microscopic zinc particles into hydrochloric acid. The results weren’t explosive, but the researchers clocked their zinc particles scooting at 1050 μm per second, or around 100 body lengths per second. To simulate that, a 2-meter-tall human would need to swim through four tar-filled Olympic swimming pools in 1 second.

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How the U.S. Army Is Turning Robots Into Team Players

Engineers battle the limits of deep learning for battlefield bots

11 min read
Robot with threads near a fallen branch

RoMan, the Army Research Laboratory's robotic manipulator, considers the best way to grasp and move a tree branch at the Adelphi Laboratory Center, in Maryland.

Evan Ackerman
LightGreen

“I should probably not be standing this close," I think to myself, as the robot slowly approaches a large tree branch on the floor in front of me. It's not the size of the branch that makes me nervous—it's that the robot is operating autonomously, and that while I know what it's supposed to do, I'm not entirely sure what it will do. If everything works the way the roboticists at the U.S. Army Research Laboratory (ARL) in Adelphi, Md., expect, the robot will identify the branch, grasp it, and drag it out of the way. These folks know what they're doing, but I've spent enough time around robots that I take a small step backwards anyway.

This article is part of our special report on AI, “The Great AI Reckoning.”

The robot, named RoMan, for Robotic Manipulator, is about the size of a large lawn mower, with a tracked base that helps it handle most kinds of terrain. At the front, it has a squat torso equipped with cameras and depth sensors, as well as a pair of arms that were harvested from a prototype disaster-response robot originally developed at NASA's Jet Propulsion Laboratory for a DARPA robotics competition. RoMan's job today is roadway clearing, a multistep task that ARL wants the robot to complete as autonomously as possible. Instead of instructing the robot to grasp specific objects in specific ways and move them to specific places, the operators tell RoMan to "go clear a path." It's then up to the robot to make all the decisions necessary to achieve that objective.

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