Functional and intelligent soft materials are useful for controlled release of medicines and other molecules. Poly(N-isopropylacrylamide) (PNIPAm) gels are well known as thermo-responsive gels with large discontinuous volume change which is commonly called as the volume phase transition. PNIPAm gels are expected to be applied to controlled-releasable material for drug delivery systems. Furthermore, we can fabricate arbitrary shapes made of gels freely by using 3D hydrogel printing techniques. Here we report that the effect of capsule shapes on behaviors of the PNIPAm objects under water flow with Reynolds number 10². In addition, we compared the behaviors of 3D-printed PNIPAm gel objects with 3D-printed polylactic acid (PLA) objects. The velocity at the first period of 2 or 3 s from the beginning of movement is slower than that of second period in the case of PNIPAm objects with ellipsoidal and bullet shapes. In other words, the capsules are accelerated after the period of 2 or 3 s. For the bullet shape objects, the velocity of the PNIPAm gel is approximately three times faster than that of PLA. It is considered that the cause of the difference between the velocities of PLA and PNIPAm gel is the difference of their frictions. The hydrogels possess commonly low friction properties. Finally, it is demonstrated that the 3D-printed PNIPAm capsules can release the solution inside the capsules by shrinking the PNIPAm gels, caused by volume phase transition.

功能性和智能性柔软的材料可用于控制药物和其他分子的释放。聚（N-异丙基丙烯酰胺）（PNIPAm）凝胶是众所周知的具有大的不连续体积变化的热响应性凝胶，通常将其称为体积相变。PNIPAm凝胶有望应用于药物释放系统的可控释材料。此外，我们可以使用3D水凝胶印刷技术自由制作由凝胶制成的任意形状。在这里，我们报道了囊形对雷诺数为10 ^2的水流下PNIPAm对象行为的影响。此外，我们比较了3D打印的PNIPAm凝胶对象与3D打印的聚乳酸（PLA）对象的行为。对于PNIPAm呈椭圆形和子弹形的物体，从运动开始的第一个2或3 s的第一阶段的速度要比第二个阶段的速度慢。换句话说，胶囊在2或3 s的时间后加速。对于子弹形物体，PNIPAm凝胶的速度大约是PLA的三倍。人们认为，PLA和PNIPAm凝胶速度差异的原因是它们之间摩擦力的差异。水凝胶通常具有低摩擦性能。最后，证明了3D打印的PNIPAm胶囊可以通过收缩由体积相转变引起的PNIPAm凝胶来释放胶囊内部的溶液。