Silk fibroin-reinforced stretchable, hyperelastic light-cured 3D printed elastomers for flexible sensors

Traditional hydrogel sensors are limited by the loss of moisture, which hinders their widespread promotion, and their relatively low mechanical properties also restrict their applications. Therefore, polymer matrices enhanced by the inherent physicochemical properties of biomass materials have received extensive attention due to their excellent mechanical performance. Light-curing technology has broken through the limitations of water, allowing for prolonged operation without moisture loss. Silk, being one of the oldest natural biomaterials, is considered one of the best natural fibers in terms of mechanical properties. The combination of the two has great potential. This study successfully fabricated the composite elastomer HEA/PSFS using light-curing 3D printing technology (LCD), after extracting natural silk into purified silk fibroin solution (PSFS) and thoroughly mixing it with the photocurable monomer (HEA). The experimental results showed that, compared with HEA, the tensile strength and toughness of HEA/PSFS were increased by 488% and 460%, respectively, while the elongation at break remained almost unchanged. In the cyclic loading and unloading tests, the hysteresis ratio for the second to the tenth cycle was no more than 6%. The Ogden model has a coefficient of determination R² > 0.95, which indicates the characteristics of a hyperelastic material. After introducing carbon nanotubes (CNTs) as a conductive medium to prepare HEA/PSFS@CNTs, the signal remained stable after continuous loading and unloading for 1600 times, with a response time of less than 150 ms. At the same time, HEA/PSFS@CNTs are capable of detecting human movement abilities. HEA/PSFS, prepared by introducing silk fibroin into the photopolymerization system, possesses strong mechanical properties, excellent electrical performance, and demonstrates significant load-bearing potential. It shows great application potential in areas such as human signal detection, Morse code, and impact resistance. This "extract-reinforce-manufacture" approach provides a novel idea for the photocuring 3D printing of elastomers and strain sensors.