4D printed self-helix structure based on internal stress reversibility

Organisms with self-helix structures are widely found in nature. Four-dimensional (4D) printing have been realized by designing structures and programming deformation of smart materials. This paper presents an innovative method of controlled self-helix structures by designing and fabricating of a bilayer structure with smart material polylactic acid. The process of applying internal stress in 4D printing was analyzed. The repeatability of helical deformation of bilayer structure was investigated. The effect of printing angle on helical deformation behavior was simulated by finite element method. And the simulation results are in good agreement with the experimental results, which also verifies the reliability of the established finite element model. Then, the stress distribution in the process of screw deformation was simulated by using the finite element model. An intelligent soft gripper was used as a case study to illustrate this methodology. This method is a guide for the design and manufacture of intelligent structures and can be applied to the design of complex biological structures.