Harvard scientists have packed the sensors and circuitry of their cockroach-sized HAMR robot into an even teeny-tinier structure the size of a penny. Dubbed HAMR-JR, the microrobot is about half the size of its previous version, but it can still carry out most of its feats, including running, jumping and carrying heavy payloads.
Small but mighty, therefore, HAMR-JR's body length is a mere 2.25 centimeters, and it weighs 0.3 grams, which is only a fraction of an actual penny. The robot can run 14 body lengths per second, making it both the smallest and the fastest microrobot out there.
Given the size of the structure, said the research team, HAMR-JR demonstrates an impressive array of actions, since most robots at this scale can only perform basic mobility tasks.
"The HAMR platform evolved from our exploration of millimeter-scale fabrication and actuation strategies," said Wood, co-author of the paper on HAMR-JR, from the Harvard Wyss Institute for Biologically Inspired Engineering. "Our techniques allow us to create robots that don't sacrifice complexity as the size is reduced and enabled us to create robots that rival some of the capabilities of their biological counterparts."
To marry the dexterous with the miniature, the scientists employed the same fabrication process that they used for HAMR-JR's previous cockroach-inspired version. The technique relies on engraving the robots' components onto 2D layers of laser-cut materials, before popping them up into a 3D structure.
PC-MEMS, as it is called (for printed circuit microelectromechanical systems), is an easier way to build complex centimeter-large 3D structures – a lot easier than the painstaking assembly of each tiny component, which in the case of microrobotics, often ends up being as inefficient as it is slow.
The researchers found that they could simply shrink the 2D design of HAMR-JR's larger version to recreate a smaller robot with the same functionalities.
"The wonderful part about this exercise is that we did not have to change anything about the previous design," said Kaushik Jayaram, the first author of the paper on HAMR-JR, from the Harvard Wyss Institute. "We proved that this process can be applied to basically any device at a variety of sizes."
The microrobot's predecessor had made a name for itself for learning how to walk on water, dive and climb, in addition to running around and jumping. Using multifunctional foot pads, the cockroach-sized HAMR could swim on water surfaces, and then use electricity to reduce tension at the surface and sink itself, in a similar fashion to a diving beetle.
Scaling the robot down, however, has changed parameters such as stride length or joint stiffness. The researchers had to develop new models for metrics including running speeds or foot forces, and it isn't clear yet whether HAMR-JR is able to swim.
Using the same pop-up mechanism, Harvard scientists have also been building microrobots inspired by the biology of bees called RoboBees, which, at about half the size of a paperclip and less than one-tenth of a gram, fly around using artificial muscles made of materials that contract when a voltage is applied.
RoboBees, in addition to flying, were designed to behave like bees: fitted with smart sensors, they can sense and respond to their environment, and coordinate their behavior to that of other robots to fly as a colony.
The research teams behind HAMR and RoboBees are confident that the microrobots will be used in various key sectors such as crop pollination, search and rescue missions, surveillance, as well as weather, climate and environmental monitoring.