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Evaporation-driven processes towards photonic colloidal assemblies
Developing patterning methods to obtain periodic and ordered colloidal films could open perspectives for their utilization in fields ranging from electronics, photonics, microfluidics or dew-harvesting (1). For instance, integrating porous nanoparticles (oxides or Metal-Organic Frameworks) in periodic structures (films or spheres) enables the fabrication of photonic devices for applications in chemical sensing (2)(3) or local thermal probing (4).
In this seminar, I will describe our initiative to develop solution processing-routes to control the assembly of nanoparticles at multiple scales. First, several methods will be discussed that involve well established techniques : (i) nanoimprint lithography of sol-gel films for light trapping in solar-cells (5) ; (ii) spray-drying assisted self-assembly of colloidal photonic balls (4).
In the second part, a new patterning method based on the self-assembly of cracks will be presented. Indeed colloidal films are obtained by evaporative processes that generate cracks, a major drawback. However, in controlled conditions, drying of colloidal droplets results in the formation of parallel periodic cracks oriented by the evaporation front-line (6).
Inspired by the formation of cracks in mud, we demonstrate that cracks can be self-assembled into periodic patterns by controlling the evaporation conditions. Arrays of periodic cracks with several geometries can be obtain without defects over several square cm. In this configuration, cracks diffract lights and can be used as photonic platform for sensing (7). This “bottom-up” method was generalized to a large variety of solution-processed materials (such as oxides) and without any limitation in terms of substrate’s shape or dimension. This simple approach enables direct integration of nanomaterials into patterned devices without the limitations of the conventional lithographic techniques.
(1) M. Faustini ; et al ACS Nano, 2018, 12, 3243
(2) O. Dalstein, et al Adv. Funct. Mater. 2016, 26, 81
(3) M. Faustini, Nat. Mater. 2021
(4) C. Avci, et al , Adv. Mater, 2021
(5) H-L Chen et al, Nat. Energy, 4, 761, 2019
(6) C. Allain, L. Limat, Physical Review Letters 1995, 74, 2981
(7) O. Dalstein ; et al , Angew. Chem. Int. Ed. 2017, 56, 14011
