Researchers at Eindhoven University of Technology have developed a tiny plastic robot, made of responsive polymers, which moves under the influence of light and magnetism.
"I was inspired by the motion of these coral polyps, especially their ability to interact with the environment through self-made currents," said researcher Marina Pilz Da Cunha. The stem of the living polyps makes a specific movement that creates a current which attracts food particles. Subsequently, the tentacles grab the food particles floating by.
The developed wireless artificial polyp is 1 by 1 cm, has a stem that reacts to magnetism, and light steered tentacles. "Combining two different stimuli is rare since it requires delicate material preparation and assembly, but it is interesting for creating untethered robots because it allows for complex shape changes and tasks to be performed," said Pilz Da Cunha. The tentacles move by shining light on them. Different wavelengths lead to different results. For example, the tentacles 'grab' under the influence of UV light, while they 'release' with blue light.
The device can grab and release objects underwater using a photomechanical polymer material that moves under the influence of light only rather than heat.
The material can hold its deformation after being activated by light. While the photothermal material immediately returns to its original shape after the stimuli has been removed, the molecules in the photomechanical material actually take on a new state. This allows different stable shapes, to be maintained for a longer period of time. "That helps to control the gripper arm; once something has been captured, the robot can keep holding it until it is addressed by light once again to release it," says Pilz Da Cunha.
By placing a rotating magnet underneath the robot, the stem circles around its axis. "It was therefore possible to actually move floating objects in the water towards the polyp, in our case oil droplets," said Pilz Da Cunha.
The position of the