Fabrication of Air-Stable and Conductive Silk Fibroin Gels

Owing to their promising applications in flexible electronics, researchers have extensively explored flexible and conductive gels. However, these gels have unsatisfactory strength and flexibility as well as easily dry in air. Herein, a rationally designed robust regenerated silk fibroin (RSF)-based gel with significant flexibility and strength, favorable conductivity, and excellent air stability is fabricated by inducing the conformation transition of RSF from random coil to beta-sheet in ionic liquid (IL)/water mixtures. We found that such RSF-based gels have a unique homogeneous network structure of RSF nanofibers, which is likely formed because of evenly distributed cross-links dominated by small-sized beta-sheet domains created during the conformation transition of RSF. Although the unique homogeneous nanostructure/network contributes toward improving the mechanical properties of these gels, it also provides pathways for ionic transport to help the gels preserve high conductivity of ILs. The prepared RSF-based gels display a remarkable air stability and reversible loss/absorption water capability in a wide humidity range environment primarily because of the distinguished combination of the IL and water. Therefore, the novel RSF-based gels hold a great potential in various applications as multifunctional, flexible, conductive materials, which are dispensed with encapsulation.