The MiniBug and WaterStrider robots measure 8.5 mm and 22 mm in length, respectively, and can move at speeds of approximately 6 mm per second.
The WaterStrider and MiniBug robots next to a coin. (Photo: Bob Hubner/WSU)
A research team at Washington State University has developed two insect-like robots named MiniBug and WaterStrider, as reported by TechXplore on January 18. These are the smallest, lightest, and fastest operational robots of their kind. In the future, these ultra-small robots could be used for various activities such as artificial pollination, search and rescue, environmental monitoring, micro-manufacturing, or surgery.
The MiniBug measures 8.5 mm and weighs 8 milligrams, while the WaterStrider measures 22 mm and weighs 55 milligrams. Both can move at a speed of about 6 mm per second. Although this is still slower than natural insects, it is considered fast compared to other ultra-small robots of similar size, according to Conor Trygstad, a doctoral researcher at the School of Materials Science and Engineering and the lead author of the study. An ant weighing 5 milligrams can move at nearly one meter per second.
The key feature of these robots is their miniature actuators that enable movement. Trygstad employed a new fabrication technique to shrink the actuators down to under one milligram, the smallest ever created. “These are the smallest and fastest actuators ever developed for ultra-small robots,” said Néstor O. Pérez-Arancibia, an expert at the School of Materials Science and Engineering at Washington State University.
The actuators use shape memory alloys, which can change shape when heated. The material is called “shape memory” because it ‘remembers’ its original shape and can return to it. Unlike conventional motors used to help robots move, these alloys do not have any moving or rotating parts.
Shape memory alloys are typically not used for larger robotic movements due to their slowness. However, for the MiniBug and WaterStrider, the actuators are made from two strands of shape memory alloy with a diameter of only 0.025 mm. With a small electric current, the wires can be easily heated and cooled, allowing the robots to flap their fins or move their legs at speeds of up to 40 times per second. In preliminary tests, the actuators were also able to lift objects over 150 times their own weight.
