  Very recently, the construction of twist actuators from magnetorheological
gels and elastomers has been suggested. These materials consist of magnetizable
colloidal particles embedded in a soft elastic polymeric environment. The twist
actuation is enabled by a net chirality of the internal particle arrangement.
Upon magnetization by a homogeneous external magnetic field, the systems
feature an overall torsional deformation around the magnetization direction.
Starting from a discrete minimal mesoscopic model set-up we work towards a
macroscopic characterization. The two scales are linked by identifying
expressions for the macroscopic system parameters as functions of the
mesoscopic model parameters. In this way, the observed behavior of a
macroscopic system can in principle be mapped to and illustratively be
understood from an appropriate mesoscopic picture. Our results apply equally
well to corresponding soft electrorheological gels and elastomers.
