Researchers at the University of California, Los Angeles (UCLA) have developed a new material to build artificial muscles that are 10 times stronger and more flexible than natural muscles, according to a university press release.
Scientists are keen to replicate the body’s muscles, which can then be used to create soft robots and new haptic technologies with a sense of touch. Materials scientists have known many soft materials that can do the dual task of delivering mechanical output while remaining viable under high strain conditions.
A class of materials called dielectric elastomers (DE) can provide both flexibility & toughness, and they are not only lightweight, but also have a high elastic energy density. DE can be made from natural or synthetic compounds and are polymers that can change size or shape when an electric field is applied. This makes it an ideal material to-make actuators, i.e. machines that can convert electrical energy into mechanical work.
What needed improvement then?
Currently, DEs are made from acrylic or silicone and while they are very useful they also have some disadvantages. DEs made from acrylic can withstand high levels of strain, but they require pre-stretching & lack flexibility. On the other hand, silicon DEs can-be made easily but fail to withstand high strain.
In collaboration with the non-profit organization SRI International (formerly known as the Stanford Research Institute), the UCLA team used commercially available chemicals and an ultraviolet (UV) light based curing process to improve acrylic based DE.
The researchers were able to modify the crosslinking in the polymer’s chain of the material to make DE softer, more flexible and more scalable without sacrificing endurance or strength. Changes in the manufacturing process have allowed researchers to make thin films of DE, which they call processable high-performance dielectric elastomers (PHDEs).
How can PHDE be used?
The PHDE film is as thin as a human hair & light-in-weight. Layering these films could help researchers create miniature actuators that can work like muscle tissue and generate enough mechanical energy to power a small robot.
Soft material has been layered before. However, the method used to do this involves the use of a liquid resin that must first be deposited and then cured. Such a “wet” process can result in an actuator with un-even layers, resulting in poor performance. Because of this, the artificial muscles you may have seen in the past are only one layer thick.
The UCLA researchers also worked on this aspect and implemented a drying process in which PHDE films are laid-down in layers using a blade and then UV-cured. The streamlined process has even allowed researchers to manufacture actuators similar to spider legs that bend & then jump, or even wind-up and then spin.
According to the press release, these new actuators can generate significantly more force than biological muscles and are 3 to 10 times more flexible than their natural counter-parts. In a demonstration, researchers showed that the actuator can toss a ball 20 times its own weight.
“This flexible, versatile & efficient actuator could open the door to artificial muscles in new generations of robotics, or in sensors and Wearable technology can more accurately mimic or even improve human like movements & abilities said Qibing Pei, a professor of materials science and engineering at UCLA.
The research has been published in the journal Science.