Giving Better Shape To Artificial Muscles

In recent times artificial muscles gained quite popularity in wake of new discoveries made with respect to flexiblility of polymer fibers that were twisted in a new geometry. These fibers give a flexing motion upon shrinking imitating the climbing motion of delicate cucumber tendrils. The best part, motion of these muscles can be controlled with heat. The research team working on this project improved the tensile characteristics of these fibers by emphasizing over their thermal properties along with their molecular framework that derives the best of its chiral structure.

The team recently discussed the details of this development in a journal letting everyone know about improved tensile strength of these fibers that kicks off as the mercury rises above 100 degree Celsius.

Guoqiang Li, the leader of this team, explains “ We analyzed the principle behind why the polymer fiber, through twisting and coiling, can behave so remarkably.” He further adds that during development they discovered two main factors: one the unwinding character of these fibers and two, negative coefficient of thermal expansion. The polymer fiber they developed addresses both these issues in a perfect manner. They have named it as the two way shape memory polymer I.e. 2W-SMP.

Where untwisting is concerned, the researchers focused on the chiral-upon-chiral characteristic on a molecular level. The stability of these molecules when they twist comes from a balanced chemical cross link framework of its molecules. The framework results in oriented molecules chains that provide significant memory characteristics to the fiber upon melting and recrystallization. The reversible crystallization also offers improved thermal expansion properties to the fiber. These get actuated with internal contraction of polymer components in heat’s presence. The thermal expansion offered by these fibers is a step ahead of their predecessors. Li says, “The actuation temperature is very high in the polymer fibers used previously, for example they can go to 160 degrees C. For some applications, like medical devices, [the] actuation temperature is too high. So you need to find a way to lower it.”