Direct Fabrication Of Hydrogel Microfibers With Embedded Helical Channel And Research On Vessel-Like Functionality

Like a magic factory,nature creates various biological materials with ingenious hierarchical structures,contributing to multifunctionalities.Materials with microchannels have attracted increasing attention due to their promising perfusability and biomimetic geometry.However,the fabrication of microfibers with more geometrically complex channels in micro-or nanoscale remains a big challenge.In this study,a novel method for generating scalable alginate microfibers with consecutive embedded helical channel is presented using an easy-made coaxial microfluidic device.No previous work has described and studied this kind of helical phenomenon.The characteristics of the helical channel could be accurately controlled by simply adjusting the flow rate ratio of the fluids.The mechanism of the helix formation process is theorized with newly proposed heterogenerated rope-coil effect,which enhances the tunability of helical patterns and promotes the comprehension of this abnormal phenomenon.The main factor is the initial flow rate ratio,which determines characteristics of the microfibers,such as morphology,diameter ratio,helix-rotating frequency and pitch of the helix.Based on this effect,microfibers with embedded Janus channels and even double helical channels are generated in situ by changing the design of the device.The uniqueness and potential applications of these tubular microfibers are also demonstrated by biomimetic supercoiling structures as well as the perfusable and permeable spiral vessel.The perfusion in helical channels with dimensions covering most parts of vasculatures broadens the possibilities of manufacturing artificial blood vessels and 3D tissues based on hydrogel microfibers.Furthermore,the different diffusion behavior between helical and straight channel indicated the important effect of vessel structures on nutrient/waste transportation.This kind of helical geometry and fabricating innovation enriched a promising possibility of creating new structure of artificial materials with which more complex 3D microenvironments could be constructed in the future tissue-engineering applications.