Pigment-less Ink Technology

<p>Here is an interesting article on a encapsulated nano structures that can produce colors that never fade. The technology uses micro encapsulated nano structures that produce color through optical interference. This could eventually applied to creating pigment-less inks for inkjet jet printers<br /><br />http://www.opli.net/opli_magazine/eo/2013/brighter-inks-without-pigment-harvard-march/</p>

<p>Pigments have been around for a very long time. Caves in southern France are painted with pigments (iron oxide, charcoal, etc) which have lasted for over 30,000 years.</p>

<p>Colors produced by nanoparticles through interference are common in nature too. The gemstone opal is an example, as are the metallic colors found in beetles and butterflies. These tend to be rather fleeting on the geological scale. Opals dry up unless sealed, taking a chalky appearance. Fossils which retain interference colors exist, but are relatively rare.</p>

<p>In a sense, nanoparticles would be considered "pigments", since they are solid particles on the same scale as normal pigments. The difference is the mechanism whereby color is produced - at the molecular level (electrons) or physical structure (interference).</p>