Soft robots: Creating a true transformer

The movement of soft robots can be remotely controlled to lock them into position for as long as needed and later reconfigure them into new shapes. Developed by researchers at North Carolina State University and Elon University, the technique relies on light and magnetic fields. ‘We’re particularly excited about the reconfigurability,’ says Joe Tracy, a professor of materials science and engineering at NC State and corresponding author of a paper on this 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,’ he explained, adding: ‘All of those things are valuable, in terms of this technology’s utility in biomedical or, for example, in aerospace applications.’ For this work, the researchers used soft robots which were made of a polymer embedded with magnetic iron microparticles.

Under normal conditions, the material is relatively stiff and holds its shape. However, researchers can heat up the material using light from a light-emitting diode (LED), which 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 – effectively locking the shape in place.

We can control the light to ensure that a robot will hold its shape at any point
Jessica Liu

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 experimental testing, the researchers demonstrated that the soft robots could be used to form ‘grabbers’ for lifting and transporting objects. Soft robots could also be used as cantilevers, or folded into ‘flowers’ with petals that bend in different directions. ‘We are not limited to binary configurations, such as a grabber being either open or closed,’ says 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.’

Additionally, the researchers 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. ‘The next steps include optimising the polymer for different applications,’ Tracy says. ‘For example, engineering polymers that respond at different temperatures in order to meet the needs of specific applications.’

31.10.2019