Multi-parameter-encoded 4D printing of liquid crystal elastomers for programmable shape morphing behaviors

Shear-induced mesogen alignments are commonly used to program the morphing behaviors of liquid crystal elastomers (LCEs) in the material extrusion process of 4D printing. The 4D printing parameters are intimately relevant to the alignment degrees and actuation strains of printed LCEs filaments. Nevertheless, there is still a lack of systematic research on the interaction of 4D printing parameters on shape morphing behavior of LCEs so far. Here, the multi-parameter-encoded 4D printing is proposed for systematically uncovering the process-structure-property relationships and programming the shape morphing behaviors of LCEs. The impact of multiple parameters (print speed, extrusion pressure, printing height, and UV light intensity) on the filament shape and actuation strains are analyzed using experiments and simulations, respectively. The role of UV light intensity on the TNI has been revealed and adopted for programming the threshold temperature, immediate state and actuation strain of printed LCEs. To demonstrate the feasibility of the multi-parameter-encoded 4D printing method, various parameters codes are integrated into the samples with the same geometric features and successfully enable distinct localized shape morphing behaviors. The multi-parameter-encoded 4D printing method allows on-demand modulation of local deformation features of LCEs structures solely through parametric design, thus providing additional design freedom and versatile tools for building soft robotics, artificial muscles, flexible electronics, etc.