The Latest Buzz in Microrobotics

Insect-scale robots, inspired by the agility and adaptability of insects, have the potential to be employed in a variety of industries where they can take on a diverse set of applications. One prominent application is in the field of environmental monitoring. Insect-scale robots equipped with sensors can navigate hard-to-reach areas, such as dense vegetation or confined spaces, to collect valuable data on environmental conditions. This could include monitoring air and water quality, tracking wildlife, or assessing the impact of climate change in intricate ecosystems.

Additionally, insect-scale robots hold promise in the medical field. These tiny robots could one day be used for targeted drug delivery within the human body, navigating through blood vessels and precisely delivering medication to specific locations. Such microrobots could revolutionize medical treatments by minimizing invasiveness and enhancing the accuracy of drug administration.

However, manufacturing tiny robots comes with a large set of challenges, primarily due to the size constraints. Finding actuators small enough to fit the miniature bodies while still providing sufficient power is a major hurdle. Actuators are crucial components that enable movement in robots, and at the insect scale, traditional actuators are too large and energy-hungry. Researchers are exploring innovative materials and mechanisms to develop compact, efficient actuators capable of generating the required forces for movement in these tiny robots.

A collaboration between engineers at Washington State University and Flyby Robotics has resulted in a significant advancement in microscale actuator technology that could help to push the field forward. They have developed a tiny, sub-one milligram actuator that is capable of lifting 155 times its own weight — that even soundly beats ants, which are well-known for their ability to carry an impressive 20 times their own weight. To demonstrate the capabilities of this actuator the team built a pair of insect-inspired robots, including an eight milligram crawler and a 56 milligram robot that can walk on the surface of water.

Piezoelectric and electromagnetic actuators are the types most frequently implemented in microrobots. However, these systems can lack sufficient power at this scale, and they have also proven to be challenging to use outside of controlled laboratory settings. For this reason, the team instead constructed a shape-memory alloy-based actuator. These materials are deformed in a predictable way when heated by an electrical current, then “remember” their original shape and snap back to it when the heat source is removed. Critically, they are lightweight and can produce a substantial amount of force.

These shape-memory alloys do have a drawback, however, in that they are too slow for many applications. The team overcame this issue by utilizing a pair of tiny shape memory-alloy wires, measuring just 1/1,000th of an inch in diameter, in each actuator. The thinness of the wires allows them to heat up and cool down very quickly, and they have been shown to be able to cycle between states 40 times per second. This property also minimizes the weight of the actuators, which weigh in at just 0.96 milligrams.

Both the crawling robot, called MiniBug, and the water-surface-tension crawler, named WaterStrider, can move at a pace of about six millimeters per second. While this is fast for microrobots, it would not impress a real insect — ants can walk at almost one meter per second. That discrepancy is likely due to the more sophisticated movements of real insects as compared to these robots than it is due to the capabilities of the actuators. But in any case, this is an important step forward. The researchers claim that their actuator is the smallest and fastest ever developed for microrobotics.

As a next step, the team is planning to build another robot based on a different insect. They are also exploring a number of options to carry the robots' power supplies onboard so that they do not need to be tethered to an external power supply.