4D printing of magnetic smart structures based on light-cured magnetic hydrogel

In recent years, with the development of materials science, various new materials that can sense external stimuli and respond have emerged. This ability to respond to external stimuli enables these materials to empower other materials or structures, greatly promoting the development of soft robots. In recent years, many 4D printed magnetic silicon gels have appeared, while 4D printing of magnetic hydrogels is still a blank slate. Here, we have developed a light-curable magnetic hydrogel that can be 4D printed. Unlike traditional methods of thickening hydrogels for 3D printing, we added bentonite to thicken the printing ink and controlled its rheological properties to make it suitable for printing. During the printing process, we used capacitive momentary discharge to generate a strong magnetic field to program the printing ink, eliminating the need for pre-treatment of the printing ink. We also studied the influence of the content of ferromagnetic particles and the size of the external magnetic field on its responsiveness. Finally, we printed and programmed the hydrogel on a silicone sheet to empower the silicone sheet. Based on this, we have created a variety of different types of soft actuators to achieve different movements and functions.