Thermochromic Silks for Temperature Management and Dynamic Textile Displays
Yang Wang, Jing Ren, Chao Ye, Ying Pei, Shengjie Ling
Abstract
Compared with synthetic polymer fibers, the unique Bombyx mori ( B. mori ) silk exhibits various benefits as a textile fiber [ 1 , 2 , 3 , 4 ]. Silk is lightweight yet strong and tough. It also has a natural sheen with high light absorbance, low static current generation, good resilience, excellent drape, and low heat conduction that makes it warm in the winter and cool in summer [ 5 ]. Direct functionalization of silk is expected to be a rational and effective strategy to develop high-performance smart textiles. To this end, different approaches have been studied, and feeding silkworm with functional components has been reported as the most direct way [ 6 , 7 ]. Carbon nanotubes [ 8 , 9 ], graphene [ 8 , 10 ], silver nanoparticles [ 11 ], metal oxide nanoparticles [ 12 , 13 , 14 ], aggregation-induced emission nanoparticles [ 15 ], and organic dyestuffs [ 16 , 17 , 18 ] have been fed to the fifth instar silkworm toward producing silk cocoons with functional nanocomponents. However, the metabolic pathway of the silkworm larva is through the digestive system [ 19 ], which is a more or less straight tube leading from the mouth to the anus. The ingested substances, such as nanomaterials, are mainly excreted, and only a limited part can enter the blood circulation system and the silk gland due to the penetration restriction of the cytomembrane. In contrast to nanomaterials, the content of small molecule additives that can enter silk gland tissue is relatively high [ 16 , 17 , 18 ], but these small molecules are mainly distributed in the sericin layer, as silk fibroin (SF) is wrapped by three layers of sericin. Hence, most of these small molecules will be removed during the degumming process, and only some dyes, such as rhodamine, can be involved in the inner SF filaments.