Reconfigurable lattice structures with programmable deformation modes under electrothermal actuation

Reconfigurable structures with programmable deformation behaviors present significant promise in fields of multifunctional antennas, flexible electronic device and soft robotics, for the capability of achieving multiple mechanical responses in a single structure. However, most previous researches have focused primarily on designing some basic deformation modes for the reconfigurable structures (i.e., shrinkage, expansion and simple shear deformation modes), which limits the exploration of a broader range of complex deformation modes in the reconfigurable structures. This study reports the design strategies for a class of reconfigurable three-phase lattice composite structures with programmable deformation modes under electrothermal actuation. The effective strain matrix is defined to characterize the finite deformation of the lattice composite structures. In addition to five basic deformation modes of the lattice composite structures, several coupled deformation modes are achieved in the lattice structures via specific actuation approaches, including bidirectional programmable shrinkage and expansion deformation, the coupled deformation modes of shearing and expansion or shrinkage. The two elements, and even three elements, of the effective strain matrices of the lattice structures are designed simultaneously, significantly enriching the deformation modes of the structures. A large deformation model is developed to describe the multiple deformation behaviors of the lattice composite structures, the accuracy of which is validated by the FEA and experimental results. Moreover, the experiments demonstrate that multiple deformation behaviors could be obtained in a single lattice composite structure by different actuation approaches. Therefore, this study offers insights for further studies into reconfigurable lattice structures with programmable deformation modes, and enhance the potential applications in fields of multifunctional antennas, flexible electronic device and reconfigurable soft robotic.