Abstract
We present a method based on a microfluidic chip that produces continuous jetting of alginate microfiber in the atmosphere to facilitate its collection and assembly. Through the analysis of the factors influencing the microfiber jetting, the principle and some microfluidic chip design criteria are discussed. A special nozzle is designed near the chip outlet, and deionized water is introduced into the microchannel through the nozzle to increase the flux and thus to prevent drop formation around the outlet which impedes the continuous jetting of microfiber. The experiments have reported the effectiveness of the proposed structure and shown that the introduction of sheath flow promotes the stability of the flow field in the microchannel and does not affect the morphology of microfiber. Simulations of velocity and pressure distribution in the microchannel are also conducted. Further, the jetting microfibers are collected and assembled into various 3D complex fiber-based macroscopic structures through patterning or reeling. Since the proposed structure is rather simple and can be easily integrated into other complex structures without adding more soft-lithographical steps, microfibers with various morphology and function can be synthesized and collected in a single chip, which can be applied to various fields, such as tissue engineering, biotechnology, and drug discovery.
Highlights
Microscale hydrogel fibers have shown great potential in many fields, such as tissue engineering, biotechnology, and drug discovery [1,2,3]
Faced with challenges with regard to collection and assembly of alginate microfiber formed through chemical reaction, we constructed a simple microfluidic chip to facilitate the continuous jetting of the microfiber
DI water was introduced into the microchannel as the sheath flow through the jetting nozzle, successfully preventing the dripping state around the outlet of microchannel
Summary
Microscale hydrogel fibers have shown great potential in many fields, such as tissue engineering, biotechnology, and drug discovery [1,2,3]. The periodic accumulate-fall down process can cause a non-negligible perturbation and even clog the microchannel, which has unfavorable effects on fiber formation To address this problem, the outlet of the microfluidic chip is usually immersed vertically into the CaCl2 solution to prevent drop formation and enable the generation of a stable jet of fiber. Considerable research has been conducted on a microfluidic liquid jet system based on hydrodynamic focusing using high pressure gas sheath or liquid flow [30,31,32] and these studies provide inspiration for us to solve the microfiber jetting problem Still, these techniques cannot be directly used in the jetting of microfiber, for not considering the microfiber’s formation process through chemical reaction. It can be applied to various situations where fiber-based macroscopic structures require precise assembly processes, such as weaving, knitting, reeling, and patterning
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