Scientists have long dreamed of creating small robots that could go through situations that are inhospitable to or dangerous for people, but it has been impossible to develop ways to keep them fueled.
An 88-milligram (0.3 ounce) “RoBeetle” that runs on methanol and employs an artificial muscle system to crawl, climb, and carry things on its back for up to two hours has recently been created by a team at the University of Southern California.
It is “one of the lightest and smallest autonomous robots ever created,” according to its creator Xiufeng Yang, measuring about 15 millimeters (.6 inches) in length. According to Yang, the lead author of an article outlining the work published in Science robotics on Wednesday, “We wanted to create a robot that has a weight and size comparable to real insects.”
The issue is that the majority of robots require motors, which are often large and energy-intensive, necessitating batteries. The team utilized a tiger beetle, which weighs 50 milligrams, as a benchmark and the smallest batteries are 10–20 times heavier.
To get around this, Yang and his coworkers created a system of artificial muscles powered by liquid fuel, in this case methanol, which has a 10x greater energy density per mass than a battery.
The “muscles” are made of nickel-titanium alloy wires, also known as Nitinol, which, in contrast to most metals, contract in length when heated. A platinum powder that serves as a catalyst for the combustion of methanol vapor was applied to the wire.
The wire shrinks when the fuel vapor from RoBeetle burns on the platinum powder, and a number of microvalves close to prevent further combustion. When the wire cools and expands, the valves are once more opened, and the cycle continues until all of the fuel has been used.
The RoBeetles’ front legs are connected to the expanding and contracting artificial muscles by a transmission mechanism, which enables it to crawl.
The group experimented with their robot on a range of flat and slanted surfaces composed of both smooth (like glass) and rough (like mattress pads) materials. Yang claimed that RoBeetle could run for two hours on a full tank and carry a load that was up to 2.6 times its own weight on its back.
On the other hand, “the smallest battery-powered crawling robot weighs one gram and operates for about 12 minutes.” Future uses for microbots could include infrastructure inspection or search-and-rescue operations following natural disasters. They could also help with environmental monitoring or artificial pollination.
RoBeetle was “an exciting microrobotics milestone,” but there were also areas for development, according to robotists Ryan Truby and Shuguang Li of MIT and Harvard, respectively.
For instance, the robot can only move continuously ahead, and by eliminating electronics, its ability to perform complex tasks is diminished.