Fig. 1. Processing of pH-responsive hydrogels based on two-photon polymerization and pH responsiveness of the structures. (a) Schematic diagram of printing by two-photon polymerization; (b) optical images of printed hand-shaped structures; (c) SEM image of the printed hand-shaped structures; (d) pH responsiveness and properties of the hand-shaped structure processed with different scanning speeds at the laser power of 20 mW; (e) pH responsiveness and characteristics of the hand-shaped structure processed with different laser powers at the scanning speed of 22500 μm/s

Fig. 2. [in Chinese]

Fig. 3. State and properties of the curved joint during the swelling process. (a) Initial state of the curved joint; (b) intermediate state during the curved joint swelling; (c) final state after the curved joint swelling; (d) swelling curve of the curved joint; (e) comparison and difference between the maximum and minimum two-end distances of the curved joint

Fig. 4. State and performance of the straight-edge joint during the swelling process. (a) Initial state of the straight-edge joint; (b) intermediate state of the straight-edge joint during the swelling process; (c) final state of the straight-edge joint after swelling; (d) swelling curve of the straight-edge joint; (e) comparison and difference between the maximum and minimum two-end distances of the straight-edge joint; (f) SEM images of the straight-edge joint

Fig. 5. Performance comparison between straight-sided and curved joints with the greatest degree of variation. (a) Swelling curve; (b) maximum two-end distance compared with minimum two-end distance and their difference

Fig. 6. Performance comparison of the curved joints with and without double-layer membrane. (a) SEM images of the curved joints with and without double-layer membrane; (b) two-end distance change curves of the curved joints with and without double-layer membrane

Fig. 7. Structural dissolution and contraction demonstration of the structures designed with curved joints. (a) SEM and optical images of “Pac-Man” structure composed of 240° curved joints; (b) SEM and optical images of daisy structure composed of 60° and 240° curved joints; (c) SEM and optical images of daisy structure composed of 120° curved joints; (d) SEM and optical images of wreath structure composed of 180° curved joints