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Poster Pitch

Optimizing droplet size for self-assembly on inclined surfaces

Monday (16.03.2020)
17:25 - 17:28
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Colloidal self‐assembly has been extensively explored for the fabrication of ordered and disordered structures for a variety of applications such as structural colors, next-generation reflective thermal barrier coatings (rTBC), porous membranes, catalysts and solid oxide fuel cells. The inspiration for the development of colloidal-based structures is often nature, ranging from structural coloration in bird feathers to broadband omnidirectional reflectors in beetles. Yet, there has been a deficit in the literature about the formation of such bioinspired materials on other than horizontally aligned and perfectly flat surfaces. In this work, we combine a 3D printing technique, direct writing, with colloidal self-assembly (AMCA) to enable the controlled and localized drop-cast of polystyrene and silica colloidal suspensions onto inclined surfaces, which subsequently assemble into photonic crystals or glasses. To simplify an overall complex process, we started by studying the printing procedure and self-assembly of single droplets onto sapphire surfaces with different tilting angles. Here, the droplet size plays a key role: next to providing a higher printing resolution, the reduction of the droplet size aids pinning of the droplet on tilted substrates, as gravitational force counteracts the adhesion and can also help hinder the coffee-ring formation [1,2]. Our results show that upon a certain volume, the shape of a pinned droplet on an inclined surface is far away from radial symmetric due to gravity driven deformation. Moreover, an intrinsic synergic effect between drop stability, coffee-ring size and structure homogeneity is found in regard to different particle compositions and size, as well as the tilting angle. These preliminary results pave the way to a better understanding of colloidal self-assembly onto inclined surfaces.


Benedikt Winhard
Hamburg University of Technology
Additional Authors:
  • Dr. Kaline Furlan
    Hamburg University of Technology
  • Prof. Dr. Gerold Schneider
    Hamburg University of Technology