Danila Maltsev

Silk fibroin (SF) derived from Bombyx mori cocoons was employed to fabricate gels using Ajisawa reagent (AJ) as the extraction medium. The resulting regenerated SF solution was subsequently directly dialyzed against an ethanol–water mixture, inducing a gradual and controllable solution–gel transition. Obtained SF gels exhibit a pronounced increase in compressive strength aligned with rising initial fibroin concentration, along with excellent water stability. FESEM, FTIR, and synchrotron X-ray diffraction analyses reveal a homogeneous network structure, likely governed by uniformly distributed physical silk II crosslinks. SF gels containing Ca²⁺ ions predominantly retain the silk I conformation, consistent with optical transparency and higher ionic conductivity. Mechanochromic SF-based gel was further developed through a one-step process involving pentacosadiynoic acid (PCDA) infiltration, followed by UV-induced polymerization into polydiacetylene (PDA), yielding a blue-colored gel. Upon compression, the PDA-infused gel exhibits a clear color transition from blue to red, demonstrating avid mechanochromic behavior. This system represents a promising platform for Structural Health Monitoring (SHM), owing to its intrinsic self-reporting capability and direct visual detectability, enabling the effective sensing of stress-induced damage and crack formation.

In this study, functional composites were developed by dispersing ZnO tetrapods (ZnO-T) in a solution of silk fibroin (SF) and formic acid (FA). Micro- and nanoparticles with different shapes were observed in the SF matrix after evaporation of the solvent, depending on ZnO-T filler content. The secondary structure of SF, as well as the shape (e.g., spherical, linear, or branched) and aspect ratio of the fillers, were investigated by FTIR spectroscopy, optical and scanning electron microscopy. While FTIR spectroscopy indicates that the secondary structure of SF is not affected by the size and shape of ZnO-T, the observed variation in effective elastic modulus measured for composites is correlated with different filler particle aspect ratios, predicting the formation of a stiff interface. We observed that branched tetrapodal fillers exhibit significant potential for optimization of composites’ mechanical properties in comparison to their spherical and linear counterparts. By combining ZnO microparticles with SF, we fabricated a stretchable strain sensor that demonstrated an appreciable improvement in the fractional change of electrical resistivity and gauge factor with respect to neat SF films.