A "paint-on" protocol for the facile assembly of uniform microgel coatings for color tunable etalon fabrication.

Robust, uniform, monolithic microgel thin films can be created by actively spreading a concentrated solution of microgels onto a Au surface at 30 °C. The method is easy, fast, and seemingly universal: it can be used to coat a variety of Au coated surfaces with microgels containing different chemical functionalities. No control of the deposition conditions, other than temperature and microgel concentration, is required. We show that this technique consistently produces monolithic microgel films on Au-coated surfaces, and it has been extended to coat Si substrates. After deposition of a thin Au overlayer onto the deposited microgel layer, the materials are colored, as evidenced by multiple peaks in their reflectance spectra. The assemblies deposited using the described "paint-on" technique show increased spectral and visual purity over the entire surface area as compared to colored materials made by a previously used passive drying process.