磁场下微通道中磁-非磁液界面不稳定性分析  

Analysis of ferrofluids-nonferrofluids interface instability in microchannels under magnetic field

作　　者：闻桂叶 焦凤 何永清 WEN Guiye;JIAO Feng;HE Yongqing(School of Chemical Engineering,Kunming University of Science and Technology,Kunming 650500,Yunnan,China;Chongqing Key Laboratory of Micro-Nano System and Intelligent Sensing,Chongqing 400067,China)

机构地区：[1]昆明理工大学化学工程学院,云南昆明650500 [2]重庆工商大学微纳系统与智能传感重庆市重点实验室,重庆400067

出　　处：《化工进展》2024年第7期3787-3797,共11页Chemical Industry and Engineering Progress

基　　金：国家自然科学基金地区基金(11962010);重庆市自然科学基金面上项目(cstc2021jcyj-msxmX0910);云南省教育厅科学研究基金(2023J0139)。

摘　　要：微通道中稳定、清晰的界面是进行颗粒进一步筛选的重要基础,将磁液作为核心流,非磁液作为鞘流有利于颗粒在外加磁场作用下进行微流控聚焦。本文基于对三相层流微流控芯片中磁液-水界面实验分析和力学模型求解,引入量纲为1数Pe、Bo_(m)、Ca、W、Re,以及表征界面颗粒运动状态的时间t_(T)、t_(d)、t_(i),得到d/h∝(X/Pe)0.633~0.852界面上力的大小依次为:磁力>界面张力>惯性力>黏性力。Q_(w)/Q_(f)=2,Q_(f)=15μL/min时,核心流的黏性耗散影响较小,界面位于通道中心处较为稳定。界面磁颗粒扩散时间t_(d)∝(X/Pe)^(0.523~0.872)在入口阶段振荡剧烈,加速流体混合,同时磁场梯度和流体扩散速度的增大会导致界面时间t_(i)∝(X/Pe)^(0.778~1.172)剧烈变化,当X=225~250时,t_(T)>t_(i)>t_(d),颗粒聚焦效率最高。The stable and clear interface in the microchannel is an important basis for further particle screening.Using the ferrofluid as the core flow and the non-magnetic fluid on both sides as the sheath flow is conducive to microfluidic focusing of particles under magnetic field.This paper is based on the experimental analysis of the ferrofluid-water interface in three-phase laminar microfluidic chip and the solution of the mechanical model.The dimensionless numbers Pe,Bo_(m),Ca,We,Re,and the time t_(T),t_(d),t_(i)to represent the movement state of the particles at the interface were introduced,and it obtained d/h∝(X/Pe)0.633~0.852.The effect of each force on the interface was in the order of magnetic force greater than interfacial tension,inertial force,and viscous force.When Q_(f)/Q_(w)=2,Q_(f)=15μL/min,the convective effect was obviously greater than the diffusion effect.In this case,the viscous dissipation effect of particles was small,and the interface was stable at the center of the channel.The diffusion time t_(d)∝(X/Pe)^(0.523~0.872)oscillated violently at the entrance stage,accelerating fluid mixing.Meanwhile,the increase of magnetic field gradient and fluid diffusion velocity will lead to a drastic change in interfacial time t_(i)∝(X/Pe)^(0.778~1.172).When X=225—250 in the middle of the magnetic field,t_(T)>t_(i)>t_(d),and the screening efficiency of magnetic swimming was the highest.

关 键 词：微通道 对流扩散 磁力 界面张力 黏性力 

分 类 号：O359.1[理学—流体力学] O353.2[理学—力学]