Development And Application Of Droplet Microreactor Based On Microfluidics Technology

ObjectiveDroplets generated in microfluidic devices have some excellent properties such as small volumes of reagents consumed,a high throughput,and high surface-area-to-volume ratio that facilitates fast reaction.As an ideal microreactor for small-scale chemical reactions,they have played a role in organic chemical synthesis and inorganic chemical synthesis.Therefore,the study of small-volume droplet-based microreactor has essential significance and value,and has a novel strategy and direction of chemical synthesis reactions.However,the permeability of PDMS which caused the evaporation of droplets influenced the reaction.In this paper,PDMS was not specially treated.The evaporation was inhibited by increasing an aqueous sacrificial layer that covering directly above droplets and to control the size of droplets,so that achieving gold nanoparticles self-assembly and synthesis of particles in the in-situ droplets formed by the array microcavity structure.The purpose of this project was to establish a method based on the microfluidic device to prevent evaporation of droplets and to manipulate the size of droplets,so as to prepare for the chemical synthesis reaction in the droplet-based microreactor.MethodsFirstly,a microfluidic chip with an array microcavity was designed,and the evaporation of in-situ droplets were evaluated,including the microfluidic chips with different materials,the evaporation under different temperature,and different pressures of the encapsulated droplets.Secondly,a sacrificial layer prevented evaporation of droplets,and droplets size was controlled by regulating dimensions of channel inside sacrificial layer and the variation of droplet volume was observed.Finally,the fluorescence intensity was amplified by concentrating droplet volume;the gold nanoparticles were patterned,the gold nanoparticles self-assembled were characterized by SEM,and the magnetic iron oxide nanoparticles were characterized by TEM.ResultsThe results showed that sacrificial single-layers were covered with a chip,in which sacrificial layer channels was filled with deionized water to keep the droplet volume from completely evaporating within 180 min,while the filler was organic phase paraffin oil or nitrogen,and the droplets were Complete evaporation loss at 80 min and 60 min;at 95 °C,sacrificial layer channels filler in deionized water in the core structure chip can maintain the volume of the droplet almost without evaporation in 30 min.However,after sacrificial layer channels filled material is replaced with the organic phase paraffin oil,droplet volume is completely evaporated in the following 140 min;microcavity covering the sacrificial layer can generate ultra-small droplet diameter can be achieved 1.22 ~ 4.0 ?m.The range of Rhodamine 123 solution droplets after concentration of the fluorescence intensity can be amplified,in which 0.02 mg/mL Rhodamine 123 droplets after evaporation concentrated detection signal can be increased to 7.24 times the initial;droplets where covering sacrificial layer of chips generated by the cross-flow shearing of gold nanoparticle solution under controlled evaporation conditions result in ordered self-assembly patterning of gold nanoparticles.The droplets of iron salt concentration was 0.0015 mg/mL mixed with ammonia water in the 'sandwich' structure chips.The reaction was heated at 60 °C to synthesize spherical magnetic iron oxide nanoparticles with relatively good dispersibility.ConclusionsBy covering the sacrificial layer microfluidics chip to prevent liquid droplets evaporation,to solve the permeability PDMS caused by internal solution evaporation.Further,droplets size is controlled by adjusting dimensions of channel inside the sacrificial layer,and at the same time,ultra-small size droplets generation is realized,avoiding unmanageable problems caused that employed a complicated system of droplets generation;The amount of sample required for different reaction systems by controlling measurement of droplet volume are achieved in order to establish a low-cost,high-efficiency droplet-based microreactor generation system.