In some embodiments, compositions and methods comprising reflective flowable materials, e.g., reflective liquids including reflective inks and/or liquid metals, are described. In some embodiments, a surface is contacted with a reflective flowable material, thereby forming a reflective layer on the surface. In some embodiments, the surface is a surface of a waveguide, for example a waveguide for a display device, and the flowable material coats surfaces of protrusions on the surface to form reflective diffractive optical elements. Some embodiments include a display device comprising a reflective layer of reflective flowable material.