Photoreversible Soft Azo Dye Materials: Toward Optical Control of Bio‐Interfaces

Photoreversible optically switchable azo dye molecules in polymer‐based materials can be harnessed to control a wide range of physical, chemical, and mechanical material properties in response to light, that can be exploited for optical control over the bio‐interface. As a stimulus for reversibly influencing adjacent biological cells or tissue, light is an ideal triggering mechanism, since it can be highly localized (in time and space) for precise and dynamic control over a biosystem, and low‐power visible light is also an inherently gentle, benign, and nondamaging stimulus in a biological environment. Azobenzene‐based dyes in particular are emerging as especially attractive candidates among photoreversible molecules, and soft azobenzene‐containing materials are promising due to their ease of incorporation, and efficient and robust photochemistry and photophysics. This review provides a current survey of the use of photoreversible azo soft materials in cell biology and tissue engineering bio‐interface applications, to afford light control over molecular motion (orientation, flow), by inscribing surface morphological patterns or macroscopically photoactuating surfaces and structures, via three key photophysical and bioactive effects enabled by the azo groups' light‐induced photo‐orientation, topological optical patterning, and photomechanical actuation.