复合结构纳米通道内溶质浓度梯度驱动的剪切流

Generation of shear flows in composite-structured nanochannels driven by solute concentration gradients

剪切流在工业生产及科学研究中有着重要作用.宏观上实现剪切流的方法依赖于机械运动部件以带动流体流动.而在微纳尺度,机械运动部件将会降低系统的稳定性,增加组装成本,不利于系统的微型化.本文提出了一种具有复合结构的纳米通道,通过调控纳米通道上下壁面与流体粒子及溶质粒子间的相互作用,实现了由溶质的浓度梯度控制的剪切流.研究表明,剪切流实现的物理机制在于扩散渗透原理:当溶质与壁面的相互作用强度大于溶剂与壁面间的相互作用,溶质被壁面吸附,流体由高溶质浓度区域流向低浓度;反之,溶质被壁面排斥,流体由低溶质浓度区域流向高浓度.通过调控溶质和溶剂与壁面间相互作用的差异及溶质的浓度梯度,可对纳米通道内剪切流的方向及大小进行精确控制.

Shear flow is crucial in industrial production and scientific research.Methods for achieving shear flow at a macroscopic level depend on mechanically moving parts that drive fluid flow.At the micro/nanoscale,mechanically moving parts reduce the stability of a system and increase its assembly costs,which is not conducive to system miniaturization.This paper proposes a nanochannel with a composite structure.Shear flow can be controlled using the solute concentration gradient realized by regulating the interaction between the upper and lower walls of the nanochannel between the solvent and solute particles.Previous studies show that the physical mechanism of shear flow lies in the principle of diffusioosmosis:the solute is adsorbed by the wall when the interaction strength between them exceeds that between the solvent and wall,following which fluid flows from a high solute concentration area to a low solute concentration area.Conversely,when the interaction strength between the solute and wall is less than that between the solvent and wall,the solute particles are repelled by the wall,and fluid flows from areas of low solute concentration to those of high concentration.The direction and magnitude of the shear flow in the nanochannel can be precisely controlled by regulating the difference between the solute-wall and solvent-wall interaction strengths and solute concentration gradient.