Mechanochromic hydrogel fibers with multiple fluorescent colors

Mechanochromic polymers can change their color in response to external force and have shown promising applications in stress sensing and failure warning. They are usually obtained as thin films or bulky specimens. The mechanochromic fibers, which can be used to make smart fabrics, have been seldom reported due to the lack of efficient fabrication techniques. In this work, a general method using photo-polymerization of microgel solution in a template tube to produce mechanochromic hydrogel fibers is reported. The obtained hydrogel fibers can generate visible and fluorescent color changes upon deformation. The diameter of the mechanochromic fibers can be easily adjusted by using different template tubes. The mechanochromic fibers can be fabricated as long as 1 m. By reducing the fiber diameter or increasing the microgel concentration, the mechanical properties of the mechanochromic fibers can be improved, leading to more obvious mechanochromic behavior. The polymethacrylate (PMA) is further used to coat the hydrogel fibers, prevent the loss of water in the fibers, and increase the storage time. The mechanochromic fibers with multiple fluorescent colors are further fabricated by utilizing different microgel solutions. This work provides an easy and effective method to fabricate mechanochromic fibers with different color change abilities.