From butterflies' wings to bank notes - how nature's colors could cut bank fraud.

Until recently, mimicking the complex surfaces of beetles and butterflies has been technologically unfeasible. The structures responsible for producing intense color are precise to the nanoscale, with repeating patterns of cuticle and air space. The manmade material was constructed with cutting-edge nanofabrication procedures, including self-assembly and atomic layer deposition. Using these techniques they were able to create the characteristic nanoscale "egg-crate" pattern that the butterfly possesses. These artificial structures could be used to encrypt information in optical signatures on banknotes, passports, or other valuable items to protect them against forgery.

Biomimicry Story

The wings of many butterflies are not pigmented. They obtain their color by physically manipulating light. The photonic structures present on their surface selectively reflect certain frequencies of light, with extreme specificity and efficiency. In this case, the source of inspiration was the Indonesian peacock or swallowtail butterfly (Papilio blumei). To the naked eye their wings appear green, but with the correct filter they appear brilliant blue. In their native rainforest, this allows the butterflies to evade predators while attracting mates.

Challenges Solved

Specific color reflection, polychromatic color, secure color imprints.