A soft robot shaped like a M枚bius strip can move when activated by light, and could be used to transport medicine and collect samples inside the body.
at Zhejiang University in China and his colleagues created their strips from thin sheets of hydrogels, materials made from long chain-like polymer molecules linked together by water molecules. They made the strips into unusual shapes, such as a M枚bius strip 鈥� a one-sided surface that results from a band with a twist in it 鈥� or a similar curved surface called a Seifert ribbon.
Advertisement
The researchers stacked the hydrogel sheets on top of each other and secured gold nanoparticles on them. When they shone light on the strips, the gold particles heated up and made the hydrogel sheets expand and twist, which, because they were aligned, meant they all moved at once.
Wu and his colleagues designed the geometry of the strips in such a way that the dark side of the ribbon slowly twists towards the light, so the ribbon can travel constantly in one direction.
Applying light in this way meant they could get the soft hydrogel robot to carry out simple tasks, such as separating and collecting plastic beads from a pile, climbing a vertical rod while carrying a bead attached by a string and reeling beads in and out while suspended from a wire (see video, above).
These sorts of tasks can be difficult for very small conventional robots, partly because the power and control mechanisms they need to run are hard to miniaturise, says Wu. The hydrogel robot, however, just needs light to operate.
While there are some soft robots that can perform similar motions, they are often complex and require more engineering, says at University College London. 鈥淚t鈥檚 a very simple idea which makes certain tasks easy.鈥�
The robot could be used inside the body for drug delivery or collecting samples, but it isn鈥檛 clear whether the driving mechanism would still work because visible light can鈥檛 easily pass through the body, he says.
Advanced Materials,
