Smart structures realize sequential motion and self-assembly through external stimuli. With the advancement of four-dimensional (4D) printing, the programming of sequential motions of smart structures is endowed with more design and manufacturing possibilities. In this research, we present a method for physically programming the timescale of shape change in 4D-printed bilayer actuators to enable the sequential motion and self-assembly of smart structures. The effects of the geometric and printing parameters on the time-dependent behavior of 4D-printed bilayer actuators are investigated. The results show that the thickness of the active layer directly affects the timescale of motion, and increasing the thickness leads to faster motion until the thickness ratio is close to 4:6. Similarly, a higher printing speed results in faster motion. Conversely, a higher printing temperature and a greater layer height result in a slower shape change. The effects of the length-width ratio, line width, and filling ratio on the timescale of motion are not as straightforward. Finally, we demonstrate several smart structures that exhibit sequential motion, including a labyrinth-like self-folding structure that is choreographed to achieve multi-step self-shaping and a flower-shaped structure where each part completes its movement sequentially to avoid collisions. The presented method extends the programmability and functional capabilities of 4D printing.

智能结构通过外部刺激实现顺序运动和自组装。随着四维（4D）打印的进步，智能结构的顺序运动编程被赋予了更多的设计和制造可能性。在这项研究中，我们提出了一种对 4D 打印双层执行器形状变化的时间尺度进行物理编程的方法，以实现智能结构的顺序运动和自组装。研究了几何和打印参数对 4D 打印双层执行器随时间变化的行为的影响。结果表明，活性层​​的厚度直接影响运动的时间尺度，增加厚度会导致运动速度加快，直到厚度比接近4:6。同样，更高的打印速度会导致更快的运动。相反，较高的打印温度和较大的层高会导致较慢的形状变化。长宽比、线宽和填充比对运动时间尺度的影响并不那么简单。最后，我们展示了几种表现出顺序运动的智能结构，包括经过精心设计以实现多步自成形的迷宫式自折叠结构，以及每个部分顺序完成其运动以避免碰撞的花形结构。所提出的方法扩展了 4D 打印的可编程性和功能能力。