Fig. 4: 2D and 3D microhydrogels fabricated via the sacrificial-scaffold-mediated TPL.

a 2D colloidal crystal microstructures with different geometries and colors. (i–iv) Optical images and (v–viii) SEM images. (ix) Optical image of a microhydrogel with neuron cell geometry. (x) SEM image of the freeze-dried hydrogel. Scare bars: 20 μm. b Reproducibility test, by printing a hydrogel microcube 54 times and measure their hue value (40 shown in the graph). Scare bar: 100 μm. c (i) design, (ii) SEM image and (iii) optical images of 3D hollow spiral microtubes fabricated by our strategy. Scare bars: 40 μm. d (i) design, (ii) SEM image and (iii, iv) optical images of a multi-color three-dimensional microhydrogel with lotus-like geometry, constructed by varying laser scanning speed (laser power = 20 mW) during TPL fabrication. Scale bars: 40 μm. e A colloidal crystal hydrogel cube frame with an inner suspended sphere. (i) design of the structure, (ii) SEM image of the freeze-dried microhydrogel and (iii) photos of the hydrogel under different conditions, revealing the suspending state of the inner hydrogel sphere. Scale bars: 20 μm. f Colloidal crystal hydrogel “bridge” constructed on a micropillar array. (i) Design of the structure, H1 = 40 μm, H2 = 10 μm, D = 10 μm, L = 60 μm. (ii) SEM image of the freeze-dried hydrogel. (iii, iv) Optical images of the microstructure. Scale bars: 20 μm for SEM images and 50 μm for optical images.