Surface Wrinkling Induced by Photofluidization of Low Molecular Azo Glasses

Gruner, Philipp; Arlt, Michael; Fuhrmann‐Lieker, Thomas

doi:10.1002/cphc.201200772

Cited by 20 publications

(15 citation statements)

References 30 publications

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“…Finally, upon release of the mechanical force an out of plane deformation is produced thus leading to buckling. Surface wrinkling exhibit several major advantages compared to other patterning approaches including its spontaneous nature, its versatility or its ability to generate large area patterns without requiring expensive lithographic techniques …”

Section: Introductionmentioning

confidence: 99%

Fabrication of hierarchical wrinkled morphologies through sequential UVO treatments

Rodríguez‐Hernández

Campo

2015

J of Applied Polymer Sci

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The fabrication, in a controlled manner, of well‐defined micrometer size topographical features on polymer surfaces is a great challenge due to the large variety of potential applications of these materials ranging from adhesion, optics to responsive interfaces. A challenging issue concerns the fabrication of interfaces having surface moieties with sizes at different length scales. Herein we describe the fabrication of hierarchical wrinkled surfaces involving two sequential ultraviolet‐ozone (UVO) treatments. This methodology allowed us to tailor the shape of PDMS surfaces and create a large variety of different patterns expected to have a broad range of applications requiring surface features with variable sizes. More interestingly, the employment of UVO treatments to produce surfaces with up to three distinct levels of order since they enable the rigidification of the interface by formation of a SiOx layer or the degradation of the PDMS surface when longer treatments. The surfaces prepared by using this approach presented patterns three different scales: the structure provided by the mask employed, the wrinkled surface inside of the directly exposed areas (related to the hole size of the mask) and the wrinkled surface protected during the first treatment by the mask (which is related to the mesh dimensions of the mask employed). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41863.

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Section: Introductionmentioning

confidence: 99%

Fabrication of hierarchical wrinkled morphologies through sequential UVO treatments

Rodríguez‐Hernández

Campo

2015

J of Applied Polymer Sci

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“…for organic glasses or polymers by heating the central layer above glass transition temperature whereas the cladding layer remains solid and prevents spinodal dewetting and thus, makes thermal wrinkling possible. Also, photoinduced approaches have been reported [36][37][38] . The morphology, the spatial wavelength Λ and the dynamics are controlled by the mechanical properties of the materials, the film thicknesses, intrinsic stresses due to the preparation as well as by the treatment for relaxation.…”

Section: Two-dimensional Wrinklementioning

confidence: 99%

Two-dimensional Wrinkle Resonators for Random Lasing in Organic Glasses

Hoinka

Ostwald

Fuhrmann‐Lieker

2020

Sci Rep

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Random lasers consisting of slab waveguides with two-dimensional disordered wrinkling patterns that act as scattering resonators are reported. As active material 2,2′,7,7′-tetraphenyl-9,9′-spirobifluorene is used which is sandwiched between an oxidized silicon wafer and a cladding with higher glass transition temperature. Wrinkles with tailorable periodicity have been induced by thermal annealing. Photopumping experiments show the transition from amplified spontaneous emission to a multiple peak laser spectrum with linewidths as low as 0.1 nm, demonstrating the applicability of this approach for random laser design.The phenomenon of random lasing has resurrected great interest recently, after its theoretical postulation 1 and experimental realization in a variety of systems 2-6 , including dye containing liquids 7,8 , powders 2,9 , scattering enhancing liquid crystals 10,11 and especially polymer-based dye-doped waveguide materials 6,12-16 . Polymers provide flexible, low cost materials with a spectral range only limited by the gain material used as dopant.Random lasing is based on amplified emission and multiple scattering in disordered media and, in literature, it is classified depending on the present feedback mechanism in either incoherent or coherent random lasing. The latter results in sharp lines based on resonant feedback loops and exist both in strongly scattering, localized regimes and in weakly scattering, diffusive regimes. Incoherent random lasers, or non-resonant feedback lasers are terms that represent a variety of light amplifications in disordered media, but they have neglectable feedback and result in a smooth, broader amplification peaks (several nm). In organic photonics, thin waveguide structures are popular for lasing devices due to easy manufacturing techniques and their compatibility with integrated optics [17][18][19] . The confinement that is introduced by the waveguide structure is often sufficient for non-resonant stimulated emission in organic laser dyes called ASE or "travelling wave lasing" without the necessity of additional confinement by a resonator, when gain is introduced. A key aspect is that the gain length needs to be large enough to exceed the losses which defines the threshold of ASE in waveguiding structures 20,21 . Similar to non-resonant feedback lasing, it results in drastic spectral narrowing for fluences above threshold. Consider a waveguide structure in an intermediate regime between slight disturbances on the surface due to increased roughness and increasing backscattering in analogy to quasi-waveguides which show losses introduced by uneven substrates. Here, the modes can still travel through the sample only that scattering at the surface is introduced. Such lossy, asymmetric slab guide systems have already been reported 13,15,16 and light amplification might be introduced due to both multiple scattering and waveguiding in a still confined, but lossy slab guide structure. For the non-resonant case, we refer to this type of emission as amplified spontaneous emissio...

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“…and optical constants (birefringence, circular dichroism, etc.) [1][2][3][4][5][6][7][8][9][10]. Azo dyes constitute a well investigated material class that represent good candidates for optoelectronic devices based on organic molecules [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…Azo dyes constitute a well investigated material class that represent good candidates for optoelectronic devices based on organic molecules [1,2]. Surface corrugation [3][4][5], holographic data storage [6][7][8][9][10], grating couplers [11], and as output control layers in organic light-emitting diodes (OLED) [12] are only few examples. Even the application in biological systems for control of biochemical processes and manipulation of physical properties is under consideration [13,14].…”

Section: Introductionmentioning

confidence: 99%