The attempt to simulate a cucumber is the first demonstration of tropism as a plant in an actuator, and is one step towards “soft” robots, which use machines made from liquid materials such as cloth, paper, fibers, and polymers, instead of solid ones. metal joints, to guide the moving parts. Softness can improve robots in situations where flexibility and minimal design are important, such as during surgery. And the autonomous soft robot can work in unpowered and unmanned environments.
“For our work, success is proving that synthetic materials can act like natural creatures—plants, for now,” Aziz said. “So we’ve provided the tools to create natural intelligence.”
Thread, of course, you can’t walk alone. It should be combined with other additional factors that make it responsive.
Aziz went through the spinning of his yarn through three different processes. One, alginate hydrogel, allows the device to absorb water. Another, hydrogel made of polyurethane, made it less expensive. The last layer was the heat transfer screen. Then he wrapped the thread around a metal rod to make it roll like a cucumber. The end looks like a long, dark magenta spring. Its smooth curves cover many layers of twisted yarn – but it’s all there.
His team tested the ability of the fiber “muscle” with several tests. First, they attach a code to the bottom of the coil. Then he gave the coil a few sprays of water. The hydrogel swelled, absorbing water. The coil came together, shrinking and pulling the paper up.
But why the swelling of the hydrogel formed a coil agreement instead of expanding? It’s because of the helical microstructure: The swelling of hydrogen pushed the helix to grow longer, and the muscle fibers become longer to compensate.
The researchers then applied heated air to a hot plate. This had the opposite effect: The coil loosened and dropped the paper. This is because the hot air helps to release the water molecules from the hydrogel, which causes the tissue to expand. (The cool air allows the molecules to return to normal, rebuilding the muscles.)
Then he asked: “Can this close the window?” (This may seem complicated, but he wanted a demonstration that the little muscle could do a useful job on its own—no power, no air tubes or wires.) move a large glass window, no matter how you turn it. So Aziz’s team created their own version of the larger plastic. The window had two panels that could be joined together to close like shutters. They weaved a little magenta fabric across both panels. With the water spray, the threads are tightened, bringing the shutters together until the window is closed.
For Aziz, the beauty of this microstructure is that its shape can change. Some muscle devices, such as shape memory, are often irreparably damaged, which prevents them from being used repeatedly. But in this case, the coil can connect or disconnect forever, responding to the atmosphere. “When it rains, it can close the window,” he says. “And when it rains, it opens the window again.”
