(Color) Schematic draft of the experimental setup for wrinkling generation in a confined PS/PVP bilayer induced by water vapor with a PDMS mold. The sealed vessel is full of water vapor for the swelling of the PS/PVP bilayer.
Optical microscope images of various wrinkles in different regions on the surface of the PS bilayer induced by water vapor in a PDMS mold (the spacing is and the area is about ). It is flat in the center of the PS/PVP bilayer. The orientation of wrinkles is changed in different regions: (a), (c), (e), and (g) are in four corners; (b) and (f) are in the middle of two ports; and (d) and (h) are at the two sides. The corresponding regions are shown by arrows.
The effect of the mold shape on the wave orientation. The waves (a) were perpendicular and (b) leaned about 45° to the orientation of the channel by mold A (rectangle) and mold B (right-angled triangle), respectively. The thicknesses of PVP and PS are 71 and , respectively. The scale bar is .
Sketch of the diffusion force in different regions. is the resultant force of part forces (perpendicular to the channels) and (parallel to the channels). The arrow shows the direction of the different forces with the water diffusion. The red dashed lines show the orientation of wrinkles in the channel of the mold.
(Color) AFM images of the surface waves formed with different thicknesses of PVP: (a) 41, (b) 71, and (c) , respectively. The thickness of PS was fixed at . Correspondingly, the periods and amplitude were (a) and , (b) and , and (c) and , respectively. The size of the images in (a)–(c) is . The lower part of every image is the AFM cross-section analysis.
Optical microscope images of the surface waves formed with different thicknesses of PS: (a) 3, (b) 10, (c) 26, (d) 97, and (e) . The thickness of PVP is . The scale bar is .
The logarithm relationship between and the multiplication product of the film thicknesses of PVP and PS.
Film thickness of the PS/PVP bilayer and the corresponding wrinkle period .
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