Modeling of photo-responsive liquid crystal elastomer actuators

Abstract

Liquid crystal elastomers (LCEs) offer promising prospect in applications such as soft robot actuators due to the fact that they can be chemically doped to have photo-responsive deformation characteristics. With the purpose of accurate control of LCE actuators in soft robot applications, the establishment of a model which quantitatively describes the deformation characteristics of LCE becomes essential. However, current models for LCE are very preliminary, which restricts the implementation of LCE actuators. This paper develops a model to describe the deformation of LCE actuators. First, the deformation process is discussed, which is in nature the macroscopic shape change corresponding to the phase change of LCE. Then, the relationship between the deformation and the temperature of LCE is established according to thermodynamic analysis on the free energy, and the phase transition process. Unknown parameters are determined through parameter identification with experimental data based on the non-linear least-squares method. This model has the advantage that it quantitatively describes the deformation characteristics of LCE without the aid of numerical simulation, and it reflects the physical nature of the deformation of LCE. This model lays a basis for the accurate control of the LCE actuators, which leads to future photo-responsive soft robot applications.