Controllable Construction of Microhelical Flows for Precise Regulation of Structural Characteristics of Microhelices

Microhelices are widely used in important fields such as biomedical engineering due to their unique structure and motion. Diverse microhelices can be fabricated by constructing microhelical flows in microfluidics based on the liquid rope coiling effect, attracting increasing attention. Here, we propose a controllable construction method for microhelical flows based on the differences in fluid viscosity and velocity, using high-viscosity polymer solution as the inner phase and low-viscosity glycerol solution as the outer phase. The pattern diagram and velocity spectra of the microfluids are established, and the boundary change relationships are analyzed. By adjusting the operating conditions, the structural characteristics of microhelical flows including pitches, diameters, amplitudes, and frequencies are precisely regulated. The physical mechanisms and regulation relationships are systematically analyzed, and the prediction formulas are established. This strategy provides significant insights for the design and fabrication of microhelices with diversified structures and functions for various applications.