Controlled Pixelation of Inverse Opaline Structures Towards Refl ection- Mode Displays
Controlled Pixelation of Inverse Opaline Structures Towards Refl ection- Mode Displays
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DOI：
10.1002/adma.201304654
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发表时间：
2014-04-01
影响因子：
29.4
通讯作者：
Yang, Seung-Man
中科院分区：
文献类型：
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作者：
Lee, Su Yeon;Kim, Shin-Hyun;Yang, Seung-Man
材料中的光子带隙由材料的折射率在光的波长的一半的长度尺度上的周期性调制产生。具有带隙范围内的能量的光子不能穿过光子晶体并被反射。[1-3]具有可见光范围内的带隙的光子晶体表现出可用于比色传感器、编码微载体和微显示器的火花干涉色。[4-8]通过结晶单分散胶体颗粒来制备光子晶体已经取得了显著的进展。排列在晶体结构中的胶体的规则阵列在空间上调制折射率，因此显示乳光结构色。[9-12]以可控方式制备高度有序的光子胶体晶体的最流行的方法之一涉及在平面基底上的对流组装。[13]在这种方法中，将基底浸入胶体悬浮液中并缓慢拉出。在回缩步骤期间，胶体集中在基板表面上的弯月面附近并形成平面蛋白石结构。胶体晶体的形状和性质可以使用各种技术进一步控制，包括微模塑、喷墨印刷和光刻。[14-24]这些技术使得能够创建微光子组件或图案化光子结构。例如，在微毛细管或微通道中模塑胶体产生具有模具形状的胶体晶体。[14-16]喷墨印刷技术还使得能够沉积由胶体悬浮液组成的液滴阵列以产生光子圆顶阵列。[17-19]已经通过光刻法制备了光子晶体的先进微图案。分散在光固化树脂中的胶体在外场下排列或结晶，然后通过光刻法将所得结构永久固定在聚合树脂中，形成彩色图案。[20然而，先前的方法具有严重限制其实际应用的若干固有缺陷。大多数蛋白石模板的微模具或液滴是脆弱的，由于其低的物理完整性。此外，光刻特征的微图案的最小特征尺寸太大或者结构的反射率对于实际使用而言不足。用于胶体晶体图案化的光刻技术中使用的光固化树脂是用于自由基聚合的单体或预聚物，而不是光致抗蚀剂，从而提供有限的微图案特征分辨率。此外，很少有方法可以产生具有复杂形状的多色微图案。因此，存在对制备具有高可控性、清晰度和反射率的光子晶体微图案的实用且可再现的方法的显著需求。在这里，我们报告了一个简单而直接的方法制备多色反蛋白石微图案相结合的对流组装的胶体颗粒与微球技术。采用蒸发诱导对流组装法在光刻胶表面垂直存款胶体晶体。晶体随后通过热退火期间的毛细管润湿完全嵌入到光致抗蚀剂基质中。嵌入在光致抗蚀剂中的晶体的光刻使得能够产生复合微图案化结构。基于光刻胶的光刻提供了图案形状的高清晰度和灵活性。选择性地去除留下规则空腔的胶体，形成在空气和聚合的光致抗蚀剂之间具有高折射率对比度的反蛋白石结构。那个...
A photonic bandgap in a material arises from periodic modulations in the refractive index of the material over a length scale that is half the wavelength of the light. Photons having an energy within the bandgap range cannot pass through the photonic crystals and are reflected.[1–3] Photonic crystals having a bandgap in the visible range exhibit sparking interference colors that are useful in colorimetric sensors, encoded microcarriers, and microdisplays.[4–8] Significant efforts have been applied toward preparing photonic crystals by crystallizing monodisperse colloidal particles. Regular arrays of colloids arranged in a crystalline structure spatially modulate the refractive index and, therefore, display opalescent structural colors.[9–12] One of most popular methods of preparing highly-ordered photonic colloidal crystals in a controllable manner involves convective assembly on a planar substrate.[13] In this approach, a substrate is dipped in a colloidal suspension and slowly pulled out. During the retraction step, the colloids concentrate near the meniscus on the substrate surface and form planar opal structures. The shape and properties of the colloidal crystals may be further controlled using a variety of techniques, including micromolding, inkjet printing, and photolithography.[14–24] These techniques enable the creation of microphotonic components or patterned photonic structures. For example, molding of colloids in microcapillaries or microchannels produces colloidal crystals with the shape of the mold.[14–16] Inkjet printing techniques have also enabled the deposition of droplet arrays composed of colloidal suspensions to produce photonic dome arrays.[17–19] Advanced micropatterns of photonic crystals have been prepared by photolithography. Colloids dispersed in photocurable resin are aligned or crystallized under an external field, and the resulting structures then are permanently fixed in polymerized resin by photolithography, making color patterns.[20, 21] However, previous approaches have suffered from several intrinsic drawbacks that have severely limited their practical applications. Most opals templated by micromolds or droplets are fragile due to their low physical integrity. In addition, the minimum feature size of lithographically-featured micropatterns is too large or the reflectivity of the structures is insufficient for practical use. Photocurable resins used in the photolithographic techniques for patterning of colloidal crystals are monomers or prepolymers for radical polymerization rather than photoresist, thereby providing a limited feature resolution of micropattern. Furthermore, few methods can produce multicolored micropatterns with complex shapes. Therefore, there is a significant demand for practical and reproducible methods of preparing photonic crystal micropatterns with high controllability, definition, and reflectivity. Here, we report a facile and straightforward method for preparing multi-colored inverse opal micropatterns by combining the convective assembly of colloidal particles with photolithographic techniques. Evaporation-induced convective assembly was used to vertically deposit colloidal crystals on the surface of a photoresist. The crystals were subsequently fully embedded in a photoresist matrix by capillary wetting during thermal annealing. Photolithography of the crystal embedded in the photoresist enabled the creation of composite micropatterned structures. Photoresist-based photolithography provided a high definition and flexibility on pattern shape. Selective removal of the colloids left behind regular cavities, forming an inverse opal structures with high index contrast between the air and the polymerized photoresist. The …