Polymers and Electronics

Electroactive polymers

Electro-mechanical coupling in soft capacitors can lead to surprisingly large deformations. Promising new applications are taking advantage of this aspect. They are known as dielectric elastomer actuators (DEA) or “artificial muscles” and have excellent properties. They can be used in a wide range of applications due to their low weight, suppleness and a deflection that can be controlled by voltage. These applications include arm wrestling robots, miniaturized pumps, optical adjustment units or electro-mechanical switches. Their simple principle gives hope to the idea that DEA-based devices will find even more diverse applications. One main reason for the wider utilization of DEAs is their high switching voltage which can reach up to a few kilovolts.

The switching voltage can, in principle, be lowered through a higher permittivity and a lower modulus of elasticity in the elastomers used, and by using the thinnest possible elastomer films. The thickness of the films is limited by the handling and the dielectric strength. This department has developed a new process to increase the permittivity of silicon-based elastomers by chemically modifying the matrix at the molecular level. To do this, suitable organic dipoles are covalently bonded to the silicon matrix. This process prevents subsequent agglomeration of the dipoles and leads to homogenous films. The chemical, thermal, mechanical and electrical properties of such films were characterized and compared to those of the corresponding base materials. The coupling of the dipoles leads to a considerable increase in permittivity as well as to a lowering of the new materials’ modulus of elasticity. This synergistic effect allows actuator elongation to be improved by a factor of six compared to conventional materials.

This process can be transferred to other material classes.