Smart cleaning of cultural heritage: a new challenge for soft nanoscience.

The search for innovative, smart and performing cleaning agents is one of the main issues of modern conservation science. Nanosciences do not only provide solutions to this scientific field in terms of new materials but also change radically the approach to problems and challenges. In this feature article we review the most innovative nanostructured systems developed in the last decade for the cleaning of artworks together with some noteworthy case studies. Micelles, microemulsions, thickened complex fluids, and responsive gels that constitute the new "cleaning palette" for modern conservators are here presented and critically analyzed. The development of these smart nanostructured systems requires the comprehension of their behavior and interactions with other materials down to the nanoscale. In the last section of this manuscript we report on the most recent results from a study about the mechanism of polymer removal from porous artifacts using nanofluids, such as micelles or microemulsions. The rules of classical detergency do not fully address the polymer removal mechanism and a schematic model of the process is proposed.