Scientists build methanol-powered beetle robot

The RoBeetle. Credit: Yang et al., Sci. Robot. 5, eaba0015 (2020)

Scientists have long envisioned building tiny robots that can navigate environments inaccessible or too dangerous for humans, but finding ways to keep them energized and moving has been impossible to achieve.

A team from the University of Southern California has now made a breakthrough by building an 88 milligram (three hundredths of an ounce) “RoBeetle” that runs on methanol and uses an artificial muscle system to crawl, climb and carry loads on. the back. up to two hours.

It is only 15 millimeters (0.6 inches) in length, making it “one of the lightest and smallest autonomous robots ever,” inventor Xiufeng Yang told AFP.

“We wanted to create a robot that was comparable in weight and size to real insects,” added Yang, lead author of an article describing the work of Science Robotics on Wednesday.

The problem is, most robots need motors which are themselves bulky and require electricity, which makes batteries necessary.

The smallest batteries available weigh 10 to 20 times more than a tiger beetle, a 50-milligram insect the team used as a benchmark.

To overcome this, Yang and his colleagues designed an artificial muscle system based on liquid fuel – in this case, methanol, which stores around 10 times more energy than a battery of the same mass.

“Muscles” are made from nickel-titanium alloy wires – also called Nitinol – which contract lengthwise when heated, unlike most metals which expand.

The wire has been coated with a platinum powder which acts as a catalyst for the combustion of methanol vapor.

As the steam from RoBeetle’s fuel tank burns onto the platinum powder, the wire contracts and a series of microvalves close to stop further combustion.

The wire cools and expands, which opens the valves again, and the process repeats until all the fuel is used up.

The expanding and contracting artificial muscles are connected to the RoBeetles’ front legs by a transmission mechanism, which allows it to crawl.

The team tested their robot on a variety of flat and sloped surfaces made from materials that were both smooth, like glass, and rough, like mattresses.

RoBeetle could carry a load of up to 2.6 times its own weight on its back and run for two hours with a full tank, Yang said.

In contrast, “the smallest battery-powered crawling robot weighs one gram and runs for about 12 minutes.”

In the future, microbots could be used for various applications such as inspection of infrastructure or search and rescue missions after natural disasters.

They can also help with tasks like artificial pollination or environmental monitoring.

Roboticists Ryan Truby and Shuguang Li, of MIT and Harvard respectively, wrote in an accompanying commentary that RoBeetle was “a milestone in microrobotics,” but added that there were opportunities for improvement as well.

For example, the robot is limited to continuous forward motion, and removing electronics from the equation reduces its ability to perform sophisticated tasks.

© 2020 AFP