Development of self-healing butterfly pea flowers extract-containing thermochromic alginate hydrogel for...

Thermochromic inks have demonstrated efficacy as a security encoding method to reduce the vulnerability of commercially accessible items to counterfeiting. However, thermochromic inks have suffered from inadequate durability. Consequently, self-healing hydrogels can serve as self-repairing inks with enhanced durability. In this context, a self-healable hydrogel with thermochromic characteristics was synthesized to serve as a self-repairing ink for anticounterfeiting and duplicable data encryption applications by combining a hybrid of cellulose nanowhiskers (CNW) and sodium alginate (ALG) with an anthocyanin (ACY)-based extract from Clitoria ternatea L. (butterfly pea flower). The use of a mordant allows the formation of the anthocyanin/mordant (ACY/Mt) nanoparticles (NPs). Cellulose nanowhiskers were employed as a dispersant to avoid the aggregation of ACY/Mt. NPs and as a reinforcing material to enhance the mechanical behavior of the prepared hydrogel. Transmission electron microscopy (TEM) was applied to determine the morphological features of ACY/Mt. NPs and CNW. CNW showed a high surface area with a crystal width of 13-28 nm and a length of 75-125 nm, whereas ACY/Mt. displayed diameters of 35-185 nm. Self-healing inks provide both endurance and thermal stability. Butterfly pea flowers were utilized to extract an anthocyanin-based eco-friendly probe. A homogeneous purple film was stamped on a paper surface. After heating the printed paper from 30 °C to 75 °C, the purplish hue (599 nm) transitioned to red (425 nm) with an isosbestic wavelength of 494 nm as demonstrated by the colorimetric coordinates. The morphological and structural features of the applied prints were tested by different analytical methodologies. The hydrogels and printed sheets were evaluated for their rheological and mechanical properties, respectively.