3D printing of magneto-active smart materials for advanced actuators and soft robotics applications

In the contemporary era, novel manufacturing technologies like additive manufacturing (AM) have revolutionized the different engineering sectors including biomedical, aerospace, electronics, etc. Four-dimensional (4D) printing aka AM of smart materials is gaining popularity among the scientific community, which has the excellent ability to make soft structures such as soft robots, actuators, and grippers. These soft structures are developed by applying various stimuli such as pH, temperature, magnetic field, and many combinations onto soft materials. Stimuli in 3D printing permit various shape-morphing behaviors such as bending, twisting, folding, swelling, rolling, shrinking, origami, or locomotion. A wide variety of soft magnetic structures can be fabricated through the incorporation of soft or hard magnetic particles into soft materials resulting in magneto-active soft materials (MASMs). With this integration, magneto-thermal coupling actuation allows diverse magneto-deformations, facilitating the development of personalized devices that are capable of enhanced deformation. In this review, guidelines are provided on the 3D printing for MASMs such as magneto-active polymers (MAPs), magneto-active composites, and magneto-active hydrogels (MAHs) on the booming development of various smart and flexible devices such as soft robots, wearable electronics, and biomimetic devices. Moreover, 3D-printed soft robotics have an outstanding capacity to adapt to complicated situations for many advanced actuating applications. Finally, some current challenges and emerging areas in this exciting technology have been proposed. Lastly, it is anticipated that technological advancements in developing smart and intelligent magneto-active structures will have a significant impact on the design of real-world applications.