An Optically Programmable Surface Realized With Azobenzene-Functionalized Lotus Leaf and OLEDs

Spatially programmable surface properties are important building blocks for future microfluidic and biosensor devices. We demonstrate switching of a photochromic surface with a blue organic light-emitting diode (OLED) suitable as an integrated on-chip light source. The surface of a positive polydimethylsiloxane replica of a fresh lotus leaf is covalently functionalized with a photoswitchable azobenzene self-assembled monolayer employing “click chemistry.” 80% of the azobenzene molecules are switched from cis to trans state within 4 min of OLED irradiation. A spatially resolved study of the azobenzene switching properties on the naturally inhomogeneous lotus surface is conducted evaluating the transmission of a 355-nm laser beam. In the area of the leaf veins the highest change in the relative transmission of 100% is obtained upon switching from trans form to cis form under UV illumination. In comparison, an azobenzene-functionalized flat glass surface exhibits only a 0.5% change in the relative transmission.