Superior Flexibility in Oxide Ceramic Crystal Nanofibers

Oxide crystal ceramics are commonly hard and brittle, when they are bent they typically fracture. Such mechanical response limits the use of these materials in emerging fields like wearable electronics. Here, a polymer-induced assembly strategy is reported to construct orderly assembled TiO₂ crystals into continuous nanofibers that are stretchable, bendable, and even knottable. Ball-milling the spinning sol and curved-drafting the electrospun nanofibers significantly improve the molecular structural order and reduce pore defects in the precursor nanofibers. Using this method, continuous TiO₂ nanofibers, in which orderly assembled TiO₂ nanocrystals (brick) are connected by twin grain boundaries or an amorphous region (mortar), are formed after sintering. Mechanical measurements and finite element analysis simulation indicate that the dislocation slip of "bricks" and the elastic deformation of "mortar" render the nanofibers with a small bending rigidity of ≈22 mN and a small elastic modulus of ≈20.8 Gpa, thus displaying properties associated with both soft and hard matter. More importantly, the reported approach can be easily extended to synthesize a wide range of soft, yet tough ceramic membranes, such as ZrO₂ and SiO₂ .