基于压力流场的高分子在微纳通道内的横向迁移行为

Cross-stream Migration of Macromolecules under Pressure Driven Flow in Micro- and Nanochannels

了解高分子在微纳通道内的流动行为对于相应的微流控器械的设计和制造至关重要。采用有限伸展非线性弹性(Finitely extendable nonlinear elastic,FENE)珠-簧链模型表示高分子链,用耗散粒子动力学(Dissipative particle dynamics,DPD)方法研究高分子在微纳通道压力流场中的横向迁移特性。研究结果表明,当微通道宽度较大,弱受限时,高分子链会远离壁面,向通道中心迁移,但高分子链浓度在通道中心处又会出现局部最小值,在通道中心和壁面之间出现峰值,高分链浓度分布呈双峰状,并且随着流场增强,向通道中心迁移越明显,排空层厚度越大,与试验结果吻合,同时随着通道宽度变大,高分子链远离壁面的趋势越强。当微通道宽度减小,强受限时,高分子链会远离通道中心,并随着流场增强,远离通道中心的趋势越强。

The flows of macromolecules in micro- and nanoscale channels are of paramount importance in the design and manufacture ofmicrofluidic devices. The macromolecules are modeled with finitely extendable nonlinear elastic （FENE） chains, and dissipative particle dynamics （DPD） approach is used to investigate the cross-stream migration of macromolecules under pressure driven flow in micro- and nanoehannels. The results show that the chains migrate away from the wall and move toward the channel centerline in wide channels where the chains are under weak confinement. In the wide channel, both the thickness of the depletion layer near the wall and the migration toward the channel centerline increase with the flow strength, and these simulation results agree well with well-known experimental observations. Under weak confinement, the center-of-mass distribution of the chains exhibits a local minimum in the centerline accompanied with two symmetric off-center peaks, and the migration away from the wall increases with the increase of channel width. However, the chains migrate away from the channel centerline in narrow channels where the chains are under strong confinement, and the migration increases with the flow strength.