Stimuli-responsive polymers that undergo reversible, complex shape-change can be synthesized by programming the molecular alignment of liquid crystal elastomers (LCEs). Alignment within LCEs has been accomplished through mechanical straining and surface treatments, but these techniques do not enable fabrication of 3D structures with locally controlled molecular alignment. Here we use additive manufacturing to spatially program molecular order in 3D creating LCE structures capable of reversible shape-change. Specifically, we use direct-write printing followed by photopolymerization of liquid crystal oligomers to create these active structures. We use this new processing method to print actuating structures with zero, positive, and negative Gaussian curvature each encoded with topological alignment patterns. By printing LCE structures with regions of both negative and positive Gaussian curvature, we leverage the continuous actuation of the heat responsive material to design structures that undergo reversible snap-through actuation in ~5 ms once a critical temperature is reached [Fig. 1]. The snapping actuation of these complex 3D structures is similar to nature’s Venus Flytrap and man-made toy ‘poppers’. This new manufacturing technique allows for simultaneous control of geometry and molecular order in active soft matter. We expect these smart structures can translate to applications in soft actuators, biomedical devices and tissue engineering.

3D printing reversible shape-changing polymeric structures

254th National Meeting (2017)

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