Figure 2. Modulation of micro-honeycomb structures.

(a,b) The same base mould was used to tune the growing bubble patterns by controlling the vacuum pressure. (a) During the initial stage, the growing bubbles were spherical in shape. (b) Under high vacuum conditions, the growing hemispherical bubbles formed a jar-like structure. (c) A gridiron-like (blue dotted line and black circles) hole arrangement produced cuboidal full-sized bubbles (orange rectangles). (d) SEM image of the cuboidal structure formed. The minimum wall thickness between cuboids was <2 μm (scale bar in the inset: 20 μm). Some misalignment events (white arrowheads) were present, indicating that unstable forces were generated as the bubbles grew. (e,f) A triangular (blue dotted lines) hole-pattern (black circles) generated a well-organized uniform hexagonal structure with a HAR. (f) SEM image of a hexagonal bubble pattern. The inset shows that the wall thickness was <2 μm (scale bar in the inset: 20 μm). (g,h) A pattern formed from holes of two sizes: 300 and 100 μm. (g) The 300 and 100 μm holes were arranged in a rectangular pattern (blue and black dotted lines). A large octagon surrounded by four small rhombus shapes was created (orange line). The small rhombus-shaped bubbles exerted supportive forces on the large octagonal bubbles. (h) SEM image of the large octagonal and small rhombus-shaped structures. The walls were ∼5-μm-thick, as shown in the inset, thicker than the walls of the rectangular and hexagonal structures (scale bar in the inset: 50 μm). (i) The 300 and 100 μm holes were arranged in triangular and hexagonal patterns, respectively (indicated by the blue and black dotted lines). A large hexagonal bubble surrounded by six small triangular bubbles was created as the bubbles expanded. (j) SEM image of the large hexagonal structures surrounded by six small triangular structures (scale bar in the inset: 50 μm). Scale bars in a,b,d,f,h and j indicate 400 μm.