Double-stretching as an effective and generalizable strategy towards thinner nanofibers in solution blow spinning

Solution blow spinning (SBS) applies high-speed airflow to prepare fibers by generating a strong stretching force. It has the advantages of scalable production, tailorable morphologies, and wide applicability. Yet, the SBS strategy can hardly prepare fibers down to the sub-100 nanometers, which limits its performance in demanding applications. Herein, we overcome the limitation of SBS by introducing a second airflow. This novel strategy is termed double-stretching SBS (DS-SBS) because an extra stretching force is exerted on the fiber when it converges with the second airflow. Polyamide6 nanofibers with an average diameter of 80 nm are successfully prepared with the DS-SBS strategy, while the SBS strategy could only prepare submicron fibers with an average diameter of 120 nm. Further, the generality of the DS-SBS strategy to reduce fiber diameter is verified on numerous solute-solvent pairs.