## 4 Applications
### Soft Robotics
Upon thermal stimulation, the printed samples deform to encircle and securely grasp objects, demonstrating stability by withstanding forces up to 30 times their weight and achieving rapid deformation and wrapping within 3 s at 60 \({}^{\circ}\)C (Figure 29c). This showcases the potential of these 4D-printed, self-deforming bionic structures for application in soft robotic grippers. [PERSON] and colleagues developed a reconfigurable, remotely actuated soft robot based on SMPCs, utilizing simultaneous magnetic actuation and photothermal heating to achieve magnetic and photo-controlled manipulation [308]. In another study, [PERSON] et al. developed bionic soft robots using a biocompatible PCL/TPU/Fe\({}_{3}\)O\({}_{4}\)@PDA nanocomposite film, employing light and magnetic fields for versatile actuation [11]. By modifying the shape of the films, various robots were created, including a flower-like robot with reconfigurable petals and a palmate robot functioning as a smart gripper. The flower-like robot achieved reversible shape transformations between lifted and flat positions, controlled by light and magnetic fields. Similarly, the palmate robot, mimicking an artificial hand, could soften under light, grasp a foam cube with magnetic fields, and release it upon reheating, demonstrating effective \"grab\" and \"release\" actions. [PERSON] and coworkers engineered an electroactive gripper based on highly conductive nanocomposite by incorporating hybrid Ag-coated CNFs (Ag@CNFs) as conductive fillers [309]. The 3D printable PLA/CNT/Ag ink with high electricity (>2.1 \(\times\) 10\({}^{5}\) S/m) enabled the gripper to produce rapid responses at different voltages, evidenced by gripping a 5 g bolt within 20 s. [PERSON] et al. designed an untethered millirobot based on MNPs containing shape-memory hydrogel that can simultaneously perform gripping motion and locomotion through an integrated electric and magnetic field system [310]. [PERSON] et al. synthesized pH-responsive shape-memory hydrogel nanocomposites incorporating zwitterionic monomers and cellulose nanocrystals (CNC), demonstrating their utility for small-scale robotic applications [31]. They constructed a robot capable of remotely navigating and steering through confined spaces to transport light cargo, utilizing a magnetic field for movement as depicted in Figure 29d. This cargo robot was magnetically guided through a maze, where an elevated pH caused it to twist and secure the cargo. Upon navigation completion, a subsequent pH increase allowed the robot to release the cargo by reverting to its original shape, showcasing the potential for precise control in targeted delivery applications. [PERSON] and colleagues demonstrated a soft robot capable of complex motion states by incorporating CNTs into a poly(ethylene-co-octene) matrix, fabricating a leopard-type robot that operated under low voltage (\(\leq\)36 V) or IR light irradiation [311]. The resulting robot exhibited movements involving the opening and closing of its legs, enabling it to advance 1 cm in 109 s, mimicking the pedaling motion of a leopard (Figure 29e). In a separate study, [PERSON] et al. developed a walking robot based on a CNT/ethylene-co-vinyl acetate (EVA) composite, requiring just 15 V driving voltage [312]. As Figure 29f demonstrates, the robot mimics animal-like continuous walking by alternating the activation of its legs, covering a distance of 3.7 cm in 48 s. Utilizing double-layer CNT-SMP composites capable of bidirectional actuation, [PERSON] and coworkers designed an inchworm robot consisting of two metal plates as moving legs [313]. The track was fashioned as a metal sawtooth with a right-triangle structure, and the front leg end was curved back to securely latch onto the metal sawtooth. Figure 29: (**a**) Illustration of a DLP-printed gripper activated by light, serving as a soft robotic hand to grab objects. Reproduced with permission from ref. [89]. Copyright 2021 John Wiley and Sons.