Robotic dragonfly skims across water to detect oil spills and acidity
From slow-moving machines inspired by sloths to others that burst from the water and soar through the air like flying fish, robots that mimic the behavior of real-world creatures have exciting potential when it comes to environmental monitoring. A new creation out of Duke University is yet another interesting example, taking after a dragonfly to skim across water and check for oil spills, high acidity and other abnormalities, and doing so without any electronics onboard.
Measuring just 2.25 inches (5.7 cm) long, the soft robot features a network of interior microchannels connected to flexible silicon tubing, which pumps air into its wings that escapes through holes in the rear to propel the robot across the water. Inflatable actuators can be used to lower these rear wings, in which case the airflow is blocked and DraBot remains stationary. In this way, the team can control which wings are up and down, and therefore the direction the robot travels in.
“Getting DraBot to respond to air pressure controls over long distances using only self-actuators without any electronics was difficult,” says team member Ung Hyun Ko. “That was definitely the most challenging part.”
To fit out their new robot for environmental monitoring, the team turned to a self-healing hydrogel they had created in an earlier research project. The material responds to changes in acidity by forming new bonds within itself, which are then reversed when pH levels return to normal. The team coated two of the DraBot's wings with hydrogel, which makes one front wing and one back wing fuse together when it enters highly acidic water.
This means that when DraBot encounters higher pH levels, it spins in circles rather than moves in a straight line. When these pH levels normalize, the fused wings separate and DraBot can be controlled once properly once again.
The team also incorporated sponges into the DraBot and doped its wings with temperature-responsive materials. When it moves through the water and encounters oil on the surface, the sponges soak up the oil and change color. When the water temperature is abnormally high, the wings turn from red to yellow. This could allow DraBot to skim across the water and both detect and cleanup oil spills, and also reveal signs of bleaching coral reefs or algal blooms through changes in water temperature. High pH levels, meanwhile, can also reveal acidifying waters that pose a threat to marine life, including coral reefs.
From here, the team hopes to make a number of improvements to DraBot. Fitting it out with an onboard propellant would eliminate the need for the silicon tubing, while it imagines adding cameras and sensors to further broaden its environmental monitoring capabilities.
“Instead of using air pressure to control the wings, I could envision using some sort of synthetic biology that generates energy,” says team member Shyni Varghese,. “That’s a totally different field than I work in, so we’ll have to have a conversation with some potential collaborators to see what’s possible. But that’s part of the fun of working on an interdisciplinary project like this.”
The video below shows the DraBot in action, while the research was published in the journal Advanced Intelligent Systems.
Source: Duke University