Patent ID: 8765484

Claim:
A freestanding optically encoded particle, comprising: a first porous layer having a predetermined first porosity and thickness; and a plurality of n additional porous layers having predetermined thicknesses and porosities, at least one of which has a predetermined porosity differing from said first porosity; wherein said predetermined porosities and thicknesses of said first porous layer and said n additional porous layers are configured to produce an interference pattern in the reflectivity spectrum having a distinct series of peaks such that the interference pattern forms an optical signature having a particular predetermined code determined by the porosities and thicknesses of said first porous layer and said n additional porous layers a receptor or targeting moiety for binding a predetermined analyte, wherein said receptor or targeting moiety is within one or more of said first porous layer and said n additional porous layers; and wherein the particle has a diameter of a few hundred microns or less and is freestanding separated from any substrate.