You've heard of robotic bees, but have you heard of robotic butterflies? Chinese researchers have published a study that focuses on their efforts to develop solar-powered wings that imitate the flapping motion of a butterfly. They were able to develop wings that can do this at a rapid rate using light-driven actuators, and a new video shows all of the different ways they can utilize what they've created.
The study was published in the journal ACS Applied Materials & Interfaces on January 16th, and a video put out on Wednesday explains how the project came together. The researchers coated a thin polymer sheet with a nanocrystalline metallic layer. When the wing was exposed to the heat of a strong light source, much like the Sun, the polymer layer on the bottom expanded significantly more than the metallic layer on the top, which caused the wing curl. The curl created shade for part of the wing, which caused the temperature to drop, which caused it to uncurl. All of this produced a rapid flapping motion.
This is one way you create a light-driven actuator, which is a material that responds to external stimuli and produces a mechanical action.
As the video shows, the team of researchers experimented with several ways their light-driven actuator could be used. They were able to attach wings to a whirligig to make it rotate in the light, they made a toy boat that could sail on water, they converted the flapping motion into electricity and more. The researchers were also able to make the actuator fold, roll, wiggle and more.
The beauty of a light-driven actuator like this one is that you can make a robot, like perhaps a robotic butterfly, that can operate without a power source other than sunlight or another strong light source. This helps make sure the robot won't be weighed down by a battery and doesn't have to be tethered to a power source. These types of robots could be used for pollination, surveillance and many other purposes.
As we reported last month, researchers are experimenting with many different ways to utilize light-driven actuators, and a team of researchers from the Netherlands recently created a robot that can walk using them. These were tiny, almost beetle-like robots, and there are many different ways these kinds of robots could be used in the future, such as delivering medicine in the body or repairing machines.
Though light-driven actuators are often used to create insect-like robots, they may soon also become the enemy of actual insects. A study that was published back in 2017 explained how one could be used to capture flies much as a Venus flytrap does. It was designed to close when a fly crossed a beam of light.
Light-driven actuators are an exciting field in robotics and beyond, but there's still a lot of work to be done with them before these concepts will be realized. In the meantime, we'll just be happy knowing we're not secretly surrounded by robot bugs.
Abstract: Light-driven actuators that directly convert light into mechanical work have attracted significant attention due to their wireless advantage and ability to be easily controlled. However, a fundamental impediment to their application is that the continuous motion of light-driven flexible actuators usually requires a periodically switching light source or the coordination of other additional hardware. Here, for the first time, continuous flapping-wing motion under sunlight is realized through the utilization of a simple nanocrystalline metal polymer bilayer structure without the coordination of additional hardware. The light-driven performance can be controlled by adjusting the grain size of the upper nanocrystalline metallic layer or selecting metals with different thermodynamic parameters. The achieved highest frequency of flapping-wing motion is 4.49 Hz, which exceeds the frequency of real butterfly wings, thus informing the further development of sunlight-driven bionic flying animal robotics without external energy consumption. The flapping-wing motion has been used to realize a light-driven whirligig, a light-driven sailboat, and photoelectric energy harvesting. Furthermore, the flexible bilayer actuator features the ability to be driven by light and electricity, low-power actuation, a large deflection, fast actuation speed, long-time stability, strong design ability, and large-area facile fabrication. The bilayer film considered herein represents a simple, general, and effective strategy for preparing photoelectric-driven flexible actuators with target performances and informs the standardization and industrial application of flexible actuators in the future.