3D printing of smart materials, called “four‐dimensional” (4D) printing, adds active, responsive functions to 3D‐printed structures. Shape memory polymers (SMPs) can be employed as an active material in 4D printing, and this could be useful for a wide range of potential applications. New design for 4D printing is presented here by introducing SMPs into rotational multistable structures. Two different digital SMPs are employed to enable large‐angle, thermal actuation in a controlled manner. It is started with bistable structures and then extending them to quadristable ones. In this design, by adjusting the thickness of SMP beams, a balance is controlled between the energy barrier and shape memory force, and this can enable controlled thermal actuation. Especially, one can control the activation time for thermal actuation. Multistable structures can simplify actuation and motion control without complicated control systems. Therefore, by adopting multistable structures in 4D printing, one can potentially enable precisely controlled, large‐magnitude, rapid actuation beyond the material capability of SMPs. These multistable structures do not require heating in the programming stage and this significantly simplifies the actuation procedure. This work provides new physical insights into 3D‐printable, active structures, and could be useful for various smart actuators responding to the environmental stimuli.

Three-dimensional (3D) printing is ideal for the fabrication of various customized 3D components with fine details and material-design complexities. However, most components fabricated so far have been static structures with fixed shapes and functions. Here we introduce bistability to 3D printing to realize highly-controlled, reconfigurable structures. Particularly, we demonstrate 3D printing of twisting and rotational bistable structures. To this end, we have introduced special joints to construct twisting and rotational structures without post-assembly. Bistability produces a well-defined energy diagram, which is important for precise motion control and reconfigurable structures. Therefore, these bistable structures can be useful for simplified motion control in actuators or for mechanical switches. Moreover, we demonstrate tunable bistable components exploiting shape memory polymers. We can readjust the bistability-energy diagram (barrier height, slope, displacement, symmetry) after printing and achieve tunable bistability. This tunability can significantly increase the use of bistable structures in various 3D-printed components.