Microfluidic-directed biomimetic Bulbine torta-like microfibers based on inhomogeneous viscosity rope-coil effect.

Helical structures are attracting increasing attention owing to their unique typical physical and chemical properties. However, it remains a challenge to construct atypical helical structures at the microscale. This paper proposes a continuous spinning method with the microfluidic-chip-based spinning device to engineer atypical helical microfibers. The strategy causes the polymer fluid to form the biomimetic bulbine-torta-like (BT) shape with the aid of the inhomogeneous viscosity rope-coil effect. In particular, the structure parameter of the BT microfibers could be optimized through the synchronous regulation of the microfluidic flow and reaction kinetics, and the obtained microfibers exhibit ultrahigh strain sensitivity, indicating great promise as exceptional candidates for constructing ideal strain sensors. In addition, single- and double-hollow BT microfibers are also prepared respectively with introducing the core flow channel into the microfluidic chip, and demonstrate high structural similarity to the irregular blood vessels (e.g. varicose veins), which is promising for the actual application of the blood vessel tissue engineering.