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. 2026 Jan 8;17:1519. doi: 10.1038/s41467-025-68237-8

Fig. 2. Quantitative characterization of multi-directional liquid spreading behaviors on bulk-cusp microstructures.

Fig. 2

Time-lapse images of droplet spreading on cross-cusp surfaces in C-pinning (a), C-mode I (b), C-mode II (c), C-mode III (d), and C-mode IV (e). (Yellow circles indicate the droplet deposition point.) f 3D bar chart of normalized spreading length L/R along the 4 orthogonal directions (x-, x+, y- and y+) for different modes, showing pronounced anisotropy spreading on cross-cusp surfaces. Bars represent mean values, and error bars indicate mean ± SD (n = 3 independent experiments). g Heatmap of maximum instantaneous spreading velocity in 4 orthogonal directions for different modes, highlighting faster transport along guided axes on cross-cusp surfaces. h Radar plots comparing normalized spreading length in 8 directions for cross-cusp and square-cusp surfaces in different modes. i Statistical comparison of anisotropy factor K between cross-cusp and square-cusp surfaces. Bars represent mean values, and error bars indicate mean ± SD (n = 3 independent experiments). j Equivalent spreading radius R′ in different modes, further quantifying the spreading areas. Bars represent mean values, and error bars indicate mean ± SD (n = 3 independent experiments). k Droplet morphologies in C-mode I–IV observed from top view for continuous injection, showing directional elongation along designed axes. l Spreading behaviors of droplets with different concentration c ethanol–water mixtures (0–100% ethanol), illustrating the dependence of spreading behaviors on surface tension. Source data are provided as a Source Data file.