Polymer溶液电渗透微流中的拉伸不稳定性
Extensional Instability in Electro-Osmotic Microflows of Polymer Solutions
摘要：
由于流体的低雷诺数特性，微流体系统中的流体输送通常是层流。悬浮聚合物的加入赋予流体弹性，当发生大量聚合物拉伸时，允许激发不稳定性。对于高分子量的聚合物链，我们发现，通过标准的电渗透泵送可实现的流速足以激发稀释的聚合物溶液中的拉伸不稳定性。我们观察到测量的波动对聚合物浓度的依赖性，其在对应于大分子溶液中的显著分子拥挤的开始的阈值处达到平台;平台发生在远低于重叠浓度的地方。我们的研究结果表明，复杂流体的电渗流从稳定的政权，建议潜在的增强混合，并需要小心模拟复杂的液体，如生物聚合物悬浮液的流动。
英文摘要：
Fluid transport in microfluidic systems typically is laminar due to the low Reynolds number characteristic of the flow. The inclusion of suspended polymers imparts elasticity to fluids, allowing instabilities to be excited when substantial polymer stretching occurs. For high molecular weight polymer chains we find that flow velocities achievable by standard electro-osmotic pumping are sufficient to excite extensional instabilities in dilute polymer solutions. We observe a dependence in measured fluctuations on polymer concentration which plateaus at a threshold corresponding to the onset of significant molecular crowding in macromolecular solutions; plateauing occurs well below the overlap concentration. Our results show that electro-osmotic flows of complex fluids are disturbed from the steady regime, suggesting potential for enhanced mixing and requiring care in modeling the flow of complex liquids such as biopolymer suspensions.
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