We propose a new method for the microfluidic spinning of ultrathin biopolymer fibers with high ordered structures by mimicking the spinning mechanism of silkworm.Researchers have reported that β-sheet crystals that are formed by means of hydrogen bonds have a key role in defining the mechanical properties of silk,and organic solvents such as methanol have been shown to affect the crystallization by inducing random coil to β-sheet transitio.Dehydration changes the conformation of silk protein domains to crystalline sheets with hydrogen bonds providing strength and stability.Therefore,as the silk fibroin immersed in a dehydrating solvent such as methanol,crystallization is induced as the silk fibroin chains undergo a transformation from random-coil to β-sheets conformation.Inspired by such crystalline structure by means of hydrogen bonding due to dehydration and physical shear of forming the basis for the mechanical strength of silk proteins in the silkworm spinning mechanism,we introduce a novel spinning method to create ultrathin,crystal-like ordered polymeric fibers within a microfluidic system.The self-aggregation was driven by dipole-dipole attraction between polar polymers upon contact with a low-polarity solvent to generate fibers with nano-strands that were highly ordered and aligned.Diverse fiber shapes and sizes from 70 nm to 20 μm could be prepared by controlling the flow rate and concentration of the extruded fluids.The induction of Kelvin–Helmholtz instabilities at the dehydrating interfaces between two miscible fluids could be used to generate multi-scale fibers in a single microchannel.Also,we successfully immobilized nanoparticles including polystyrene and graphite without any additional process and devices.