Fig. 1. Femtosecond laser two-photon processing. (a) Optical path diagram of femtosecond laser two-photon processing system; (b) diagram of anisotropic cross section by femtosecond laser two-photon processing; (c) relationship between degree of polymerization of hydrogel micro-block and hatching distance with optical micrograph of deformation of block processed at 24 mW energy shown in inset; (d) effect of R on bending curvature of hydrogel cantilever beam with optical micrographs of cantilever beams with different R at same energy shown in inset and scale bar of 10 μm

Fig. 2. Micro-actuators with bidirectional motion. (a) 1-arm microstructure; (b) 2-arm microstructure; (c) 6-arm microstructure; (d) ipsilateral 2-arm microstructure

Fig. 3. Micro-assemblies prepared by LPCS technology at room temperature. (a) Optical micrograph of printed anisotropic hydrogel microplates in solution with anisotropic cross-section design of microplate shown in inset; (b) wire contact microplate prepared by self-assembly; (c) optical micrograph of printed anisotropic hydrogel four-leaf clover in solution with anisotropic cross-section design of four-leaf clover shown in inset; (d) multi-contact four-leaf clover prepared by self-assembly

Fig. 4. Reversibility analysis of line contact microstructures prepared with different materials. (a) Diagram and optical micrograph of assembled hydrogel microstructures; (b) diagram and optical micrograph of microstructures in Fig.4(a) after immersion in solution; (c) diagram and optical micrograph of assembled liquid photoresist microstructures; (d) diagram and optical micrograph of microstructures in Fig.4(c) after immersion in solution

Fig. 5. Reversible preparation of microsensors. (a) Diagram of reversible drive of microsensor; (b) optical micrograph of microsensors in solution at room temperature; (c) optical micrograph of assembled microsensors with SEM shown in inset and scale bar of 20 μm; (d) optical micrograph of microsensors in solution at temperature higher than T_c