Soft robotic dragonfly detects environmental conditions in water

Engineers at Duke University developed an entirely soft robot shaped like a dragonfly designed to skim across the water's surface and react to environmental conditions. The robot, called DraBot, is entirely electronics-free and reacts to environmental conditions like pH, temperature, or the presence of oil. Researchers believe that the proof of principle demonstration unit could be the precursor to a more advanced autonomous and long-range environmental robot able to monitor for a range of issues.

Researchers on the project began by designing a soft robot based on a fly. After several iterations, researchers settled on the shape of a dragonfly engineered with a network of interior micro-channels allowing it to be controlled via air pressure. The body of the robot is about 2.25 inches long with a 1.4-inch wingspan.

The body of the robot was created by pouring silicon into an aluminum mold and then baking it. Interior channels were created using soft lithography, and it was connected with flexible silicon tubing. Researchers were challenged by getting DraBot to respond to air pressure controls over long distances using self-actuators without any electronics.

DraBot works by controlling the air pressure that enters its wings. The microchannel squeezes air into the front wings, where it escapes through series of holes pointed into the back wings. When the back wings are down, the airflow is blocked, and DraBot remains stationary. When both wings are up, DraBot moves forward.

The team also designed balloon actuators under each rear wing close to the robot's body. When those are inflated, the balloons cause the wings to move upward, allowing controllers to tell the robot where to go. The wings are painted with a self-healing hydrogel that makes them responsive to changes in the water pH.

When the water is acidic, one front wing fuses with the back wing causing the robot to spin in a circle rather than travel in a straight line. When the pH returns to normal, the fused wings separate, and the bot is responsive to commands. The researchers also placed sponges on the robot that will soak up oil and change color, indicating its presence. DraBot's wings also change from red to yellow color if the water is too warm.