Programmable pattern transformation via size-encoded thermal expansion of digital light processing 3D-printed polymer

Stimuli-responsive pattern transformations are prevalent in nature and play a crucial role in numerous applications. Inspired by nature, the majority of man-made pattern-programmable structures are realized by triggering the strain mismatch of multiple stimuli-responsive materials. However, the integration of heterogeneous materials introduces technical challenges in the manufacturing and interfacial design. Herein, we realize heat-responsive pattern transformation of planar lattices by employing the size-encoded thermal expansion of the single-vat digital light processing (DLP) 3D-printed polymer. A mapping relation has been experimentally established among the projection pattern size, local average light intensity, and the coefficient of thermal expansion (CTE) of the DLP-printed polymer. Upon heating, strain mismatch is triggered among areas of different CTEs, resulting in Euler buckling of the lattice struts. To guide the design of the pattern-programmable lattices, we develop a theoretical model to predict the critical buckling temperature of the unit cell struts and perform finite element simulations to capture the buckling pattern of the lattice structures. Both theoretical predictions and numerical calculations agree well with experimental results. Specifically, we show an intelligent locking device and an information carrier to demonstrate the potential applications of pattern-programmable lattices.