Photoswitchable adhesives using azobenzene-containing materials.

Photoinduced reversible solid-to-liquid transitions of azobenzene-containing materials can control adhesion. Photoswitchable adhesives based on azobenzene-containing small molecules and polymers are under intense investigation. The melting points or glass transition temperatures of such azobenzene-containing materials in trans and cis forms are above and below room temperature, respectively. Photoswitching of these materials results in reversible trans-cis isomerization and solid-to-liquid transitions. The solid trans azobenzene-containing materials have strong adhesion and the liquid cis azobenzene-containing materials have weaker adhesion. In this Minireview, we introduce adhesives based on azobenzene-containing small molecules and polymers. The remaining challenges and perspectives in the field of photoswitchable adhesives using azobenzene-containing materials are also discussed.