Microfibers From Microfluidics And Their Biomedical Applications

Microfibers are regarded as elements of various fiber-shaped materials,from plants vessels,spider silk fibers,to springs,optic fibers,bundled wires,and widely used in the fabrication of higher-ordered nano-/micro scale materials.In biomedical engineering,microfibers are building blocks of functional three-dimensional objects and hierarchical structures because of their long,thin and flexible features.Inspired by the features of these structural-functional adaptations,considerable attention and effort have been devoted into the creation of these fibrous materials.The developed methods and approaches include electrospinning,drawing,melt spinning,dry spinning,and template based,etc.Each of them is suitable to different situations.However,microfibers made via these traditional fabrication methods often have homogenous chemical composition or structures and experience narrow material choosing,strict processing procedure.These shortcomings restrict the applications of these products in most cases.Thus,alternative microfluidic approaches have been introduced to address these limitations.Microfluidics deals with,precisely controls,and systematically manipulates the behavior of fluids constrained in small cross-sectional channels.In addition,the high integration of microfluidic systems improves the coexistence and diversifies interactions of multiple fluids.Such features enable the fabrication of micro-and nanoscale structures with diverse shapes,configurations and functionalities,especially of microfibers.Thus,in this thesis,we fabricate several kinds of microfibers with complex microstructures and functions using microfluidic spinning approach and explore their applications in biomedical engineering.The detailed works are as follows:(1)Based on laminar flows,core-shell structures microfibers laden with metal-organic frameworks were generated.By designing microfluidic device with hierarchical injection channels and choosing appropriate inner precursor solutions,core-shell microfibers with hydrogel shells and metal-organic frameworks synthesized in situ in the core could be generated continuously.The shell of microfiber could control the release of the laden metal ions in the metal-organic frameworks,and the microfibers could show potential in wound healing.(2)Adjusting flow rates in the microfluidic channel,helical microfibers could be generated in a coaxial capillary microfluidic device.By transforming the microfluidic device with hierarchical or multi-barrel injection channels,helical microfibers with multilayered or multicompartmental structures were fabricated.These helical microfibers could show good responsiveness when functional nanoparticles or polymers were introduced.They could also act as templates for producing helical microswimmers by integrating lithography with microfluidics.(3)Based on the core-shell structured helical microfibers,by employing ionic liquid as core flow,helical microfibers with conductivity were fabricated.The coflow microfluidic device were used to produce helical microfibers with core-shell structures and encapsulate ionic liquid in their cores,which could impart the microspring with reliable conductivity.These conductive microsprings could work as conductors in flexible electronics.