Programming crack patterns with light in colloidal plasmonic films

Abstract Crack formation observed across diverse fields like geology, nanotechnology, arts, structural engineering or surface science, is a chaotic and undesirable phenomenon, resulting in random patterns of cracks generally leading to material failure. Limiting the formation of cracks or “programming” the path of cracks is a great technological challenge since it holds promise to enhance material durability or even to develop low cost patterning methods. Drawing inspiration from negative phototropism in plants, we demonstrate the capability to organize, guide, replicate, or arrest crack propagation in colloidal films through remote light manipulation. The key consists in using plasmonic photothermal absorbers to generate “virtual” defects enabling controlled deviation of cracks. We engineer a dip-coating process coupled with selective light irradiation enabling simultaneous deposition and light-directed crack patterning. This approach represents a rare example of a robust self-assembly process with long-range order that can be programmed in both space and time

Periodic nanoporous inorganic patterns directly made by self-ordering of cracks

International audienceSolution-processed inorganic nanoporous films are key components for the vast spectrum of applications ranging from dew harvesting to solar cells. Shaping them into complex architectures required for advanced functionality, often need time-consuming or expensive fabrication. In this work, we show how crack formation is harnessed to pattern porous inorganic films in a single step and without using lithography. We developed aqueous ink formulations that, in the presence of polymeric latexes, enable evaporation-induced, defect-free periodic arrays of cracks with tunable dimensions over several centimeters. The ink formulation strategy was generalized to more than ten inorganic materials including simple and binary porous oxide and metallic films covering a whole spectrum of properties including insulator, photocatalytic, electrocatalytic, conductive or electrochromic materials. Notably, this approach enables three-dimensional self-assembly of cracks by stacking several layers of different compositions, yielding periodic assemblies of polygonal shapes and Janus-type patterns. The crack patterned periodic arrays of nanoporous TiO2 diffract light, and are used as temperature-responsive diffraction grating sensors. More broadly, this method represents a unique example of self-assembly process leading to long-range order (over several cm) in a robust and controlled way