Researchers at the University of Wollongong (UOW) in Australia have created artificial muscles inspired by the supercoiling of DNA strands.
DNA is one of the most impressive examples of compressive force in nature. It is she who allows you to twist threads about 2 meters long and place them in one human cell. To do this, DNA uses a supercoiling process. Let us recall that supercoiling is the phenomenon of twisting of topologically closed DNA chains, as a result of which the axis of the double helix of DNA itself twists into a spiral of a higher order. By “topologically closed” we mean molecules, the free rotation of the ends of which is difficult (circular DNA molecules or linear molecules, the ends of which are fixed by protein structures). Aside from DNA, a similar effect can be seen in everything from matted garden hose to headphone wires.
In a new study, UOW scientists have replicated this phenomenon when creating artificial muscles. Biologists made them from polyester composite fibers coated with a hydrogel that swells when wet. They were twisted into a DNA helix and then submerged in water to swell.
This usually leads to unraveling of the fibers. However, scientists have found that if you clamp their ends, then they undergo supercoiling. As a result, the threads generate a relatively large amount of mechanical force.
In the experiment, supercoiled fibers shrank to 10% of their original length, generating the equivalent of 1 Joule of energy per gram. The mechanical work that a muscle from such filaments can perform is 36 times higher than that of a comparable human skeletal muscle.
However, while the samples are moving rather slowly due to the mechanism of action of the hydrogel. However, scientists claim that the process can be accelerated by changing the materials or production methods of artificial muscles, leaving the fibers supercoiled.