Engineering news
US Researchers have developed a new electroactive polymer material that can change shape and size when exposed to a relatively small electric field.
The electroactive polymer developed North Carolina State University (NCSU) material could potentially be used in applications such as microrobotics, designer haptic, optic, microfluidic and wearable technologies.
Richard J. Spontak, professor of chemical and biomolecular engineering and materials science and engineering at NCSU, said: “Dielectric elastomers are the most responsive electroactive polymers in terms of achievable strains, but two big hurdles have effectively prevented the smart materials community from using them in commercial devices. First, previous dielectric elastomers required large electric fields in order to trigger actuation, or movement.
“The second challenge is that materials had to be pre-strained. This would either mean using a frame to physically strain the material, or adding a second component to the polymer to retain the strain after it was applied. But our material consists of a single component that is specifically designed at the molecular level to inherently possess pre-strain. We don’t need a frame or a second component, our material is ready to be used as soon as it is cross-linked into a specific shape.”
The new material that has permitted this advancement is a “bottlebrush” silicone elastomer, which has been engineered to possess these specific properties, and is not difficult to manufacture.
Sergei S. Sheiko, professor of chemistry, said: “The polymers are prepared by grafting long polymeric side chains to a polymer backbone. The resulting molecules may be viewed as filaments that are thick, yet remain quite flexible, which allows for significant reduction of the materials’ rigidity and makes them more stretchable. The mechanical properties can be controlled by varying the bottlebrush architecture – for example, by preparing molecules with different degrees of polymerisation of grafted chains and different grafting densities.
“This architectural control of mechanical properties has reduced the limit of stiffness in dry polymer materials by 1,000 times, demonstrated extensibility of up to eight times, and opened up new applications not available to stiffer materials or materials with liquid fractions.”
NCSU worked in collaboration with researchers from the University of North Carolina at Chapel Hill, Carnegie Mellon University and the University of Akron.