Azo Polymer Microspherical Cap Array: Soft-Lithographic Fabrication and Photoinduced Shape Deformation Behavior

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• 作者：Bin Liu ; Yaning He ; Pengwei Fan ; Xiaogong Wang
• 刊名：Langmuir
• 出版年：2007
• 出版时间：October 23, 2007
• 年：2007
• 卷：23
• 期：22
• 页码：11266 - 11272
• 全文大小：967K
• 年卷期：v.23,no.22(October 23, 2007)
• ISSN：1520-5827

文摘

In this work, azo polymer microspherical cap arrays possessing unique photoprocessible properties have beenfabricated through a soft-lithographic contact printing approach. In the process, hexagonal polystyrene (PS) colloidalarrays, obtained by the vertical deposition method, were used as masters. Poly(dimethylsiloxane) (PDMS) stamps withaligned hemisphere air voids on the surfaces were obtained by casting the precursor against the colloidal arrays. Byusing the stamps and a solution of an epoxy-based azo polymer (BP-AZ-CA) as "ink", the microspherical cap arrayswere fabricated by pressing the "inked" surfaces against substrates. Uniform 2D arrays of the submicrometer sphericalcaps could be obtained on the substrates after peeling off the stamps and drying. The characteristic sizes of the arraysdepended on some adjustable features, such as the diameters of PS spheres and concentrations of the "inks" used inthe process. After exposure to a linearly polarized Ar⁺ laser single beam, the spherical caps could be stretched alongthe polarization direction, and the arrays were consequently transformed into ellipsoidal cap arrays. Upon irradiationof interfering p-polarized Ar⁺ laser beams, only the spherical caps in the bright fringes were deformed by the lightirradiation, which resulted in more complicated surface relief patterns. The observation gives another well-definedexample of the photoinduced mass migration in the submicrometer scale. The approach can potentially be appliedto fabrication of microlens arrays with different converging rate in two directions.