A group of researchers from the University of Freiburg has created a new type of artificial muscles that are made entirely of naturally occurring proteins and organic compounds. In response to external stimuli these muscles contract in exactly the same way as their living prototypes, and this will make it possible to use this technology not only in robotics, but also to create prostheses and implants for the next generations.
Almost all artificial muscles that we have heard about before are too “artificial in nature”, in most cases they are made of different kinds of plastics, nylon, rubber and even carbon nanotubes. Such devices are ideal for robots and various automatic devices, but the use of man-made materials makes them incompatible with human body tissues.
Researchers from the University of Freiburg solved the problem of biocompatibility by using elastin, a naturally occurring protein that gives tissues of the skin, blood vessels their elasticity. However, the researchers made some changes in the protein structure that made it sensitive to two external factors – changes in temperature and acidity of the environment. At the same time, exposure to one of the factors leads to muscle contraction, and the second causes the opposite effect – their relaxation.
Eventually, a biological artificial muscle was born, driven by sodium sulfide, which is a product of an “oscillatory” chemical reaction. The whole process is triggered by raising the temperature to a point above 20 degrees Celsius, which causes periodic changes in the pH level, forcing the muscle to contract and relax.
Changes in ambient temperature and the concentration of components for chemical reactions make it possible to realize very precise control over the process of contraction of artificial muscles. Scientists have also developed a number of control algorithms, which will allow a device consisting of several artificial muscles installed in different directions to perform certain actions.
Along with applications in the field of so-called “soft robotics,” this kind of biocompatible artificial muscles can be used to create implantable devices that will not be rejected by the human body. “In the future, we are going to refine the artificial muscle material so that it becomes sensitive to some additional factors, such as the concentration of certain salts in the environment,” the researchers write, “We also plan to change the ‘energy source’ for biological artificial muscles; we plan to switch them to being powered by some amino acids that can easily be obtained from biomass.”
