A Review of Bioinspired Superhydrophobic Materials and Their Applications in Heritage Conservation

New material research is one of the important focus for heritage conservation. A qualified material can not only protect the physical and chemical integrity of cultural objects, but also preserve their artistic and aesthetic features. They shall well conserve the authenticity of cultural heritage. Learning from the well-established methods and materials employed for research in materials science is a common approach for developing new materials for art conservation. Bioinspired superhydrophobic materials are a general term for a class of materials which were fabricated by studying the special wetting phenomena observed on many biological surfaces in nature. As one of the priorities in materials science research recently, they have gradually attracted the attention of conservation scientists. As a matter of fact, liquid water is directly or indirectly related to the deterioration of many different types of cultural objects. Superhydrophobic materials, yet, are particularly suitable for hydrophobization on artworks. Owing to their excellent hydrophobicity, superhydrophobic materials can effectively prevent the adhesion, penetration of liquid water and the condensation of water vapor, thus greatly relieving water-induced decay phenomena. More importantly, the superhydrophobic surfaces equipped with self-cleaning property, on which water contact angle is more than 150° while the contact angle hysteresis is less than 10°, can spontaneously clean the dirt, dust attached to the surface, restoring the artistic features simultaneously. These characteristics of super-antiwetting materials are very significant for artwork conservation, especially for those exposed in open air. Based on the analysis of the basic principle of bionic superhydrophobic materials, this paper summarizes several preparation methods of bionic superhydrophobic materials in the field of cultural relics protection, briefly expounds the concrete examples, application prospects and unique advantages of this kind of materials in the hydrophobic treatment of stone cultural relics, metal cultural relics, wood cultural relics and textiles, and self-cleaning protection. In addition, it points out the main problems that bionic superhydrophobic materials can not be widely used in cultural relics protection, that is, the shortage of material types and the lack of long-term monitoring of material properties. Finally, this review prospects the future research and development direction of this kind of materials.