Data_Sheet_1_4D Printing Dual Stimuli-Responsive Bilayer Structure Toward Multiple Shape-Shifting.docx

4D printing has been attracting widespread attention because its shape and performance can change under stimuli. The existing 4D printing technology is mostly limited to responsive to single stimulus, which means that the printing structure can only change under a pre-specified stimulus. Here we propose a 4D printing strategy with dual stimuli-responsive shape-shifting that responds to both temperature and water, by using a direct ink writing 3D printing method to deposit a polyurethane elastomer material with water-swelling characteristics on a heat-shrinkage shape memory polymer material to form a bilayer structure. Based on the systematic study of the adapted printing parameters of the polyurethane elastomer, the effect of programmable variables on the deformation shape was investigated. The diversified printing structure exhibits rich structural changes under one or both of the two stimuli of temperature and water. This research provides a universal multiple stimuli-responsive 4D printing method, which can effectively improve the intelligent responsiveness of 4D printing structures by combining multiple smart materials.

4D打印（4D printing）凭借可在外界刺激下实现形状与性能的动态变化，受到广泛关注。现有4D打印技术大多仅支持单一刺激响应，即打印制备的结构仅能在预设的单一刺激条件下发生形变。本研究提出一种可同时响应温度与水双重刺激的形状变形4D打印策略：采用直写式3D打印（Direct Ink Writing）工艺，将具备吸水溶胀特性的聚氨酯弹性体（polyurethane elastomer）沉积于热收缩型形状记忆聚合物基材表面，构建双层复合结构。在系统研究聚氨酯弹性体适配打印参数的基础上，本研究探究了可编程调控变量对打印结构形变形态的影响规律。多样化的打印结构可在温度、水单一刺激或二者协同刺激下呈现丰富的形变行为。本研究提出了一种通用型多刺激响应4D打印方法，通过复合多种智能材料，可有效提升4D打印结构的智能响应性能。