Most attempts at giving robots muscles tend to be heavy, slow or both. Scientists might finally have a solution that's both light and nimble, though. They've developed fibers that can serve as artificial muscles for robots while remaining light, responsive and powerful. They bonded two polymers with very different thermal expansion rates (a cyclic copolymer elastomer and a thermoplastic polyethylene) that reacts with a strong pulling force when subjected to even slight changes in heat. They're so strong that just one fiber can lift up to 650 times its weight, and response times can be measured in milliseconds.
As a cucumber plant grows, it sprouts tightly coiled tendrils that seek out supports in order to pull the plant upward. This ensures the plant receives as much sunlight exposure as possible. Now, researchers at MIT have found a way to imitate this coiling-and-pulling mechanism to produce contracting fibers that could be used as artificial muscles for robots, prosthetic limbs, or other mechanical and biomedical applications. While many different approaches have been used for creating artificial muscles, including hydraulic systems, servo motors, shape-memory metals, and polymers that respond to stimuli, they all have limitations, including high weight or slow response times. The new fiber-based system, by contrast, is extremely lightweight and can respond very quickly, the researchers say.
Many robotic designs take nature as their muse: sticking to walls like geckos, swimming through water like tuna, sprinting across terrain like cheetahs. Such designs borrow properties from nature, using engineered materials and hardware to mimic animals' behavior. Now, scientists at MIT and the University of Pennsylvania are taking more than inspiration from nature -- they're taking ingredients. The group has genetically engineered muscle cells to flex in response to light, and is using the light-sensitive tissue to build highly articulated robots. This "bio-integrated" approach, as they call it, may one day enable robotic animals that move with the strength and flexibility of their living counterparts.
The stretchable optical lace material was developed by Ph.D. student Patricia Xu through the Organics Robotics Lab at Cornell University. "We want to have a way to measure stresses and strains for highly deformable objects, and we want to do it using the hardware itself, not vision," said lab director Rob Shepherd, associate professor of mechanical and aerospace engineering and the paper's senior author. "A good way to think about it is from a biological perspective. A blind person can still feel because they have sensors in their fingers that deform when their finger deforms. Robots don't have that right now." Shepherd's lab previously created sensory foams that used optical fibers to detect such deformations.
Soft robotics is a rapidly growing field with applications ranging from prosthetics to space exploration. Now a research team out of Yale University has taken the technology one step further with the invention of smart, robotic fabric that can change its shape and stiffness on the fly. The key to the material's capabilities lies within the fibers themselves. The team, led by Dr. Rebecca Kramer-Bottiglio, spun epoxy into fibers that can vary their stiffness thanks to the particles of Field's metal embedded within them. Field's metal is novel in that it liquefies at very low temperatures.