Fig. 2: Design of the master mold.

a, b Schematics of major design variables for CFIC, where \({{{{{{\boldsymbol{d}}}}}}}_{{{{{{\boldsymbol{t}}}}}}}\) is the micropillar tip diameter, \({{{{{\boldsymbol{h}}}}}}\) is the height of the subpillar, \({{{{{{\boldsymbol{r}}}}}}}_{{{{{{\boldsymbol{c}}}}}}}\) is the center-to-center radius, and \({{{{{\boldsymbol{\delta }}}}}}\) is the deflection of a pillar. c, d Schematics of a hierarchical pillar being bent to capillary interaction force when partially immersed in a liquid. e Three-dimensional plot of the critical conditions for each collapse type. f Plot depicting critical conditions for CFIC and clustering angle of the pillar tips. The design point should lie in the desirable design region to induce the clustering of upper pillars while avoiding lateral collapse. g Top wireframe view of the designed hierarchical pillar array template. h Isotropic view of the designed pillar array template.