Azobenzene derivatives are the molecules of choice for both fundamental and applied research on photoswitchable (supra)molecular self-assemblies and materials with reversible photocontrol over their macroscopic properties. Their potential stems from the reversible trans–cis photoisomerization and relative ease of synthetic modification, allowing for (i) tuning the lifetime of the metastable cis-state from sub-milliseconds up to several years, and (ii) designing the molecular structure to respond to virtually any color of visible (and near-UV) light. Today, these molecular “engines” are being explored for applications spanning from medicine to energy technologies and (tunable) photonics.

Azobenzene, or azobenzene-based materials, have many faces. Herein, I would like to reveal some of them, with particular focus on our recent work on azobenzene-containing thin-film-based optical humidity sensing and photoinduced surface patterning. The former is enabled by molecular design that sensitizes the lifetime of the cis-state to environmental humidity. The latter, in turn, utilizes fast-switching azobenzenes and their photoinduced mass migration in response to irradiation with laser interference patterns. The potential use of the resulting surface patterns as cell-instructive surfaces as well as diffractive optical elements for AR/VR technologies will be discussed.

Why these particular examples? Because in addition to revealing some of the faces of azobenzene, they showcase our efforts in translating fundamental science into practical applications.