# Recent Developments in Materials Science for the Conservation and Restoration of Historic Artifacts
## 6 Smart Materials--A Potential Breakthrough in Heritage Science
### Case Studies  
[PERSON] et al. [123] described the reinforcement of the San Paolo Eremita church in Brindisi (Italy) with a prototype device developed by the authors based on the superelastic properties of shape-memory alloys (Ni-Ti SMAs), in order to enhance the properties of metal tie-rods found in the structure of the building. Based on the results of laboratory testing performed before pilot application, the authors suggest an improvement in the thermal and seismic behavior of the restored heritage building. The potential application of SMAs was also proposed in other studies. For example, [PERSON] et al. [124] proposed the use of SMAs as a highly effective solution in enhancing earthquake resilience in historic masonry structures, with a focus on addressing vulnerabilities observed after the 2003 Bam earthquake (Iran). Their hypothesis centers on the unique properties of SMAs, including superelasticity, shape retention, and energy dissipation, which help mitigate seismic stress without harming a structure's historical aesthetics or materials. The primary findings of the study highlight that SMAs can significantly reduce damage in both small-scale tests and structural models, demonstrating that they reduce displacement and stress concentrations during simulated seismic events. The research emphasizes SMAs' compatibility with fragile masonry materials, allowing them to absorb seismic energy more efficiently than traditional materials. These properties make SMAs particularly suitable for heritage structures, which often face limitations in traditional retrofitting methods to maintain aesthetic and cultural value. [PERSON] et al. [125] evaluated the potential application of hydrogels based on semi-interpenetrating poly(2-hydroxyethyl methacrylate)/poly(vinylpyrrolidone) networks containing water-based cleaning systems via a comparison with an agar-agar hydrogel. For the proposed formulation, several parameters were analytically investigated (including water retention and release properties, mesoporous, and microstructure). When applied on the canvas painting, the proposed hydrogel led to superior results, compared with agar-agar: no color leaching was observed for brazilwood ink, while, in terms of cleaning efficiency, for the indigo colorant (the most sensitive layer of the artifacts), the color difference (\(\Delta\)E\({}^{*}\)) was reduced from 12.6 (before cleaning) to 2.1 (after two twenty minutes of treatment with the proposed hydrogel). Also, the results of the FTIR-ATR evaluation demonstrated that no gel residues were left on the canvas, thus allowing the authors to support the application of the hydrogels as advanced systems for the cleaning of water-sensitive artifacts. The efficiency of differently formulated hydrogels for the cleaning of real metal artifacts was recently presented by [PERSON] [126], including the successful application in cleaning artifacts of copper, gilded copper and copper alloys, lead, painted aluminum, and vermeil gold, supporting the further used of agar hydrogels. [PERSON] et al. [127] presented the application of a new surfactant-synthesized nanoconsolidant on a Romanesque church (Church of Santa Maria del Campo, A Coruna, Spain), by comparison with two commercial consolidants (acrylic resin and ethyl silicate). The nanoconsolidant was obtained starting from a sol consisting of a silica oligomer and a surfactant, without the addition of any solvent. After extensive laboratory tests, the authors applied the consolidant on deteriorated stonework from the selected site by brushing. The results of the peeling test revealed that the procedure led to a considerable reduction in the materials stripped off by adhesive tape, demonstrating the effectiveness of the consolidant (between 60% and 98% reduction) in providing resistance to the salt crystallization process. Considering the recorded color changes, the results represented a minimum risk of incompatibility (with color changes recorded between 2.03 and 3.05).