title: Engineering functionality gradients by dip coating process in acceleration mode.
abstract: In this work, unique functional devices exhibiting controlled gradients of properties are fabricated by dip-coating process in acceleration mode. Through this new approach, thin films with "on-demand" thickness graded profiles at the submillimeter scale are prepared in an easy and versatile way, compatible for large-scale production. The technique is adapted to several relevant materials, including sol-gel dense and mesoporous metal oxides, block copolymers, metal-organic framework colloids, and commercial photoresists. In the first part of the Article, an investigation on the effect of the dip coating speed variation on the thickness profiles is reported together with the critical roles played by the evaporation rate and by the viscosity on the fluid draining-induced film formation. In the second part, dip-coating in acceleration mode is used to induce controlled variation of functionalities by playing on structural, chemical, or dimensional variations in nano- and microsystems. In order to demonstrate the full potentiality and versatility of the technique, original graded functional devices are made including optical interferometry mirrors with bidirectional gradients, one-dimensional photonic crystals with a stop-band gradient, graded microfluidic channels, and wetting gradient to induce droplet motion.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, UMR 7574, Chimie de la Matière Condensée de Paris, F-75005 Paris, France.
authors.forename: Marco
authors.initials: M
authors.lastname: Faustini
authors.forename: Davide R
authors.initials: DR
authors.lastname: Ceratti
authors.forename: Benjamin
authors.initials: B
authors.lastname: Louis
authors.forename: Mickael
authors.initials: M
authors.lastname: Boudot
authors.forename: Pierre-Antoine
authors.initials: PA
authors.lastname: Albouy
authors.forename: Cédric
authors.initials: C
authors.lastname: Boissière
authors.forename: David
authors.initials: D
authors.lastname: Grosso
keywords: dip-coating; gradient; photonics; thin films; wetting