Soft robots controlled by light and magnetic field

Researchers are using light and magnetic fields to remotely control the movement of soft robots, an advance with potential applications in the biomedical or aerospace sectors.

magnetic field
Rotation of a ‘flower’ with six petals. Turning on the LED in sync with the rotation of every second petal beneath the magnet causes lifting of alternating petals, which remain lifted (Photo: Jessica A.-C. Liu)

The technique from North Carolina State University and Elon University, North Carolina, allows the team to lock soft robots into position for any given time and later reconfigure them into new shapes.

“We’re particularly excited about the reconfigurability,” said Joe Tracy, a professor of materials science and engineering at NC State and corresponding author of a paper on the work. “By engineering the properties of the material, we can control the soft robot’s movement remotely; we can get it to hold a given shape; we can then return the robot to its original shape or further modify its movement; and we can do this repeatedly. All of those things are valuable, in terms of this technology’s utility.”

According to NC State, the team used soft robots made of a polymer embedded with magnetic iron microparticles. Under normal conditions, the material holds its shape but light from an LED makes the polymer pliable. Once pliable, researchers demonstrated that they could control the shape of the robot remotely by applying a magnetic field. After forming the desired shape, researchers could remove the LED light, allowing the robot to resume its original stiffness, essentially locking the shape in place.

By applying the light a second time and removing the magnetic field, the researchers could get the soft robots to return to their original shapes. Or they could apply the light again and manipulate the magnetic field to move the robots or get them to assume new shapes.

In experiments, the researchers are said to have demonstrated that the devices could be used to form grabbers for lifting and transporting objects. The soft robots could also be used as cantilevers.

“We are not limited to binary configurations, such as a grabber being either open or closed,” said Jessica Liu, first author of the paper and a PhD student at NC State. “We can control the light to ensure that a robot will hold its shape at any point.”

The researchers also developed a computational model that can be used to streamline the soft robot design process. The model allows them to fine-tune a robot’s shape, polymer thickness, the abundance of iron microparticles in the polymer, and the size and direction of the required magnetic field before constructing a prototype to accomplish a specific task.

“Next steps include optimising the polymer for different applications,” Tracy said in a statement. “For example, engineering polymers that respond at different temperatures in order to meet the needs of specific applications.”

The paper, “Photothermally and Magnetically Controlled Reconfiguration of Polymer Composites for Soft Robotics,” appears in Science Advances.