This Robot Will Blow You Away!

With electric vehicles filling up the headlines these days, battery technologies are getting a lot of attention from researchers. This attention has given rise to major advances in recent years, with a focus on improving energy density, charging speed, and overall durability. As a result, consumers can now enjoy longer ranges, faster charging times, and more reliable performance from their electric vehicles. Additionally, these advancements are not limited to just the automotive industry; they have the potential to revolutionize various sectors, including robotics, renewable energy storage, and portable electronics.

But despite the hype, the fact of the matter is that batteries still cannot compete with chemical fuels when it comes to energy density. Fuels like methanol and butane are twenty to fifty times more energy dense than the best present battery technologies.

Moreover, batteries can be quite heavy and bulky. And the same can be said for the electric motors that they drive. This may be acceptable for some applications, like vehicles, but it is a deal breaker at smaller scales. Consider an insect-scale robot, for example. The battery would be likely to weigh more than the rest of the robot’s components combined, and scaling electric motors down to such small sizes would be a big challenge as well.

Researchers at Cornell University have gone against the grain of present trends in developing a new type of actuation system for an insect-scale quadrupedal robot. They have developed a tiny internal combustion engine with an integrated actuator that packs a big punch. With one of these actuators powering each of the two pairs of legs, the team’s robot can jump high up into the air — well, high considering its diminutive size, anyway.

Each actuator weighs only 325 milligrams and can produce 9.5 newtons of force per combustion cycle, with up to 100 cycles being possible every second. Similar to larger-scale engines, the actuator takes in a mixture of explosive vapors (methane and oxygen), then a spark in the chamber ignites it. But rather than moving a traditional piston, the pressure from the explosion inflates a soft elastomer membrane. The cycle is completed by venting the spent gasses.

The tiny weight of the engine is somewhat misleading, however. The fuel and sparking mechanism are kept external to the robot, being delivered via tubing and wires. This certainly limits the applications that a robot leveraging this technology could be used for. Moreover, there are some considerations around the durability of the engine. It was reported that the actuator can operate continuously for 750,000 cycles without degrading in performance, which sounds impressive. However, that only translates to about 8.5 hours of operation at a rate of 50 cycles per second. Exactly how the engine behaves after that amount of wear is not clear.

But the performance of the tiny, 1.6 gram, 29 millimeter robot is quite impressive in any case. It is capable of walking while carrying a burden 22 times its own weight, and it can jump 59 centimeters straight up into the air. These metrics are near to insect-level performance, which is notable because nature is very hard to beat.

The researchers pointed out that the robot need not be quadrupedal. Slug- or bee-like designs, for example, could be powered by the actuators in theory. But one issue that the team is working through is how to slow the actuator down. At present it must cycle very rapidly, which is not appropriate for all use cases. In addition to working through this problem, the team is also exploring options to untether their robot from external devices.