Department of Polymer Engineering, University of Akron , Akron, Ohio 44325, United States.
Chemistry Department, Faculty of Science, King Saud University , PO Box 2455, Riyadh 11451, Saudi Arabia.
ACS Appl Mater Interfaces. 2017 Jun 21;9(24):20928-20937. doi: 10.1021/acsami.7b00779. Epub 2017 Jun 9.
Synthetic topographically patterned films and coatings are typically contoured on one side, yet many of nature's surfaces have distinct textures on different surfaces of the same object. Common examples are the top and bottom sides of the butterfly wing or lotus leaf, onion shells, and the inside versus outside of the stem of a flower. Inspired by nature, we create dual (top and bottom) channel patterned polymer films. To this end, we first develop a novel fabrication method to create ceramic line channel relief structures by converting the oligomeric residue of stamped poly(dimethylsiloxane) (PDMS) nanopatterns on silicon substrates to glass (SiOx, silica) by ultraviolet-ozone (UVO) exposure. These silica patterned substrates are flow coated with polystyrene (PS) films and confined within an identically patterned top confining soft PDMS elastomer film. Annealing of the sandwich structures drives the PS to rapidly mold fill the top PDMS pattern in conjunction with a dewetting tendency of the PS on the silica pattern. Varying the film thickness h, from less than to greater than the pattern height, and varying the relative angle between the top-down and bottom-up patterned confinement surfaces create interesting uniform and nonuniform digitized defects in PS channel patterns, as also a defect-free channel regime. Our dual patterned polymer channels provide a novel fabrication route to topographically imprinted Moiré patterns (whose applications range from security encrypting holograms to sensitive strain gauges), and their basic laser light diffractions properties are illustrated and compared to graphical simulations and 2D-FFT of real-space AFM channel patterns. While traditional "geometrical" and "fringe" Moiré patterns function by superposition of two misaligned optical patterned transmittance gratings, our topographic pattern gratings are quite distinct and may allow for more unique holographic optical characteristics with further development.
合成的地形图案薄膜和涂层通常在一侧形成轮廓，而许多自然表面在同一物体的不同表面上具有明显的纹理。常见的例子是蝴蝶翅膀或荷叶的顶面和底面、洋葱壳以及花朵茎的内表面和外表面。受自然启发，我们创建了双（顶和底）通道图案聚合物薄膜。为此，我们首先开发了一种新颖的制造方法，通过将压印的聚二甲基硅氧烷（PDMS）纳米图案在硅衬底上的低聚物残留物转化为玻璃（SiOx，二氧化硅）来创建陶瓷线通道浮雕结构，通过紫外线-臭氧（UVO）暴露。这些硅石图案化的衬底用聚苯乙烯（PS）薄膜进行流涂，并限制在相同图案的顶约束软 PDMS 弹性体薄膜内。三明治结构的退火会促使 PS 迅速填充顶部 PDMS 图案，同时 PS 在硅石图案上发生去湿倾向。改变薄膜厚度 h，使其小于或大于图案高度，并改变自上而下和自下而上图案化约束表面之间的相对角度，会在 PS 通道图案中产生有趣的均匀和不均匀的数字化缺陷，以及无缺陷的通道区域。我们的双图案聚合物通道提供了一种新的制造路线来形成地形压印莫尔图案（其应用范围从安全加密全息图到敏感应变计），并展示了它们的基本激光光衍射特性，并与图形模拟和实空间 AFM 通道图案的 2D-FFT 进行了比较。虽然传统的“几何”和“条纹”莫尔图案通过两个错位的光学图案透射光栅的叠加来起作用，但我们的地形图案光栅是非常独特的，并且可能允许进一步开发具有更多独特全息光学特性的莫尔图案。
