Robust natural biomaterial based flexible artificial skin sensor with high transparency and multiple signals capture

The human skin tissues were full of elastic collagen networks to keep water, mechanical strength and capture tactile signals. Learn from this, it is highly desired to use natural biomaterials especially protein host materials to prepare artificial skin with excellent mechanical property, highly transparent and multi-sensing. In this work, we first demonstrate a natural silk fibroin (SF) membrane based artificial skin enhanced by cellulose nanocrystals (CNCs). CNCs here acted as cross-linked sites to contribute to dynamic network formation in SF membrane through intermolecular hydrogen bonding interaction. The inner structure, transparency, thermal stability, mechanical properties and possible sensing mechanism of SF/CNCs membranes were carefully investigated as a function of varied CNCs contents. The results indicated that the optimized Young's modulus of SF/CNCs membrane with 15 wt% CNCs greatly increased to 960 MPa (withstanding 10,000 times its own weight), while the transparency still reached up to 90%. More importantly, the SF/CNCs membranes showed excellent multiple sensing of small tactile signals and low concentration (0.2 mg/mL) of ethanol gas, resulting from the dynamic reversible network between CNCs and SF molecular chains. Such versatile and robust SF/CNCs membranes will be very potential in artificial skin used in special place such as chemical plants.