Ferrofluids exhibit significant thixotropic behaviors under a magnetic field, which are induced by the presence and evolution of different microstructures.

Traditional printed products have to some extent affected the development of smart structures and their application in multiple fields, especially in harsh environments, due to their complex mechanisms and control principles. The 4D printing technology based on magnetically controlled smart materials exploits the advantages of magnetically controlled smart materials with good operability and security, and its printed smart structures can be obtained under magnetic field drive for unfettered remote manipulation and wireless motion control, which expands the application of printed products in complex environments, such as sealed and narrow, and has broad development prospects. At present, magnetically controlled smart material 4D printing technology is still in its infancy, and its theory and application need further in–depth study. To this end, this paper introduces the current status of research on magnetically controlled smart material 4D printing, discusses the printing process, and provides an outlook on its application prospects.

The yielding of ferrofluids conforms to a very shear thinning type.

As a novel functional nanomaterial, Fe₃O₄ magnetic nanoparticles (MNPs) modified by different surfactants have attracted and are attracting worldwide interest. In this research, we introduced two different silane coupling agents to modify Fe₃O₄ MNPs instead of a single surfactant to achieve complete coating and functionalization. The modification mechanism was also explained. Techniques such as TEM, XRD, FT-IR, TG-DSC, and VSM were applied to characterize the obtained modified Fe₃O₄ sample. From these techniques, the following information is obtained: The characteristic bands of TEOS and KH-792 were present in the FT-IR spectra and in the XPS plots of modified Fe₃O₄ MNPs, demonstrating that the silane coupling agents were present in the sample obtained after the modification. The TG analysis of the modified sample showed complete decomposition at 228 °C. The mass ratio of the sample obtained before and after the modification was close to 29:65. The XRD patterns show that the modified Fe₃O₄ MNPs possessed an identical reverse spinel crystal structure as an unmodified Fe₃O₄ sample. The modification decreased the saturation magnetization of Fe₃O₄ MNPs from 70.04 emu/g to 57.41 emu/g and the coating did not change the superparamagnetism of Fe₃O₄ MNPs.

This article provides a comprehensive exploration of the current research landscape in the field of soft actuation technology applied to bio-inspired soft robots. In sharp contrast to their conventional rigid counterparts, bio-inspired soft robots are primarily constructed from flexible materials, conferring upon them remarkable adaptability and flexibility to execute a multitude of tasks in complex environments. However, the classification of their driving technology poses a significant challenge owing to the diverse array of employed driving mechanisms and materials. Here, we classify several common soft actuation methods from the perspectives of the sources of motion in bio-inspired soft robots and their bio-inspired objects, effectively filling the classification system of soft robots, especially bio-inspired soft robots. Then, we summarize the driving principles and structures of various common driving methods from the perspective of bionics, and discuss the latest developments in the field of soft robot actuation from the perspective of driving modalities and methodologies. We then discuss the application directions of bio-inspired soft robots and the latest developments in each direction. Finally, after an in-depth review of various soft bio-inspired robot driving technologies in recent years, we summarize the issues and challenges encountered in the advancement of soft robot actuation technology.