Direct observation of confinement-induced diffusophoresis.
Direct observation of confinement-induced diffusophoresis.
复制标题
直接观察限制诱导的扩散电泳。
DOI：
10.1088/1361-6528/ab31f7
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发表时间：
2019
期刊：
影响因子：
3.5
通讯作者：
Riehn,Robert
中科院分区：
文献类型：
--
作者：
Movahed,Saeid;Azad,Zubair;Dangi,Saroj;Riehn,Robert
纳米流体装置的通道尺寸在普通水溶液的德拜长度的一个数量级之内。在纳米流体器件中，通常采用外部驱动来产生离子和生物分子的浓度极化。在这里，我们证明了所有纳米流体装置固有的远程离子强度梯度，即使在平衡状态下，也会驱动大分子的漂移。为了证明这种效果，我们将长DNA限制在恒定矩形截面（100× 100 nm 2）的直纳米通道中，这些通道连接到大型微流体储层。DNA的运动在没有任何驱动的情况下被观察到。我们发现，在低离子强度下，纳米通道中的分子向纳米微界面迁移，而在高盐条件下则是纯粹的扩散运动。利用数值模型，我们证明了即使在平衡状态下，微纳界面上的运动也与离子强度梯度一致，并且漂移的主要原因是扩散泳动。
Nanofluidic devices have channel dimensions which come to within one order of magnitude of the Debye length of common aqueous solutions. Conventionally, external driving is used to create concentration polarization of ions and biomolecules in nanofluidic devices. Here we show that long-range ionic strength gradients intrinsic to all nanofluidic devices, even at equilibrium, also drive a drift of macromolecules. To demonstrate the effect, we confine long DNA to straight nanochannels of constant, rectangular cross-section (100× 100 nm 2) which are connected to large microfluidic reservoirs. The motion of DNA is observed in absence of any driving. We find that at low ionic strengths, molecules in nanochannels migrate toward the nano-micro interface, while they are undergoing purely diffusive motion in high salt. Using numerical models, we demonstrate that the motion is consistent with the ionic strength gradient at the micro-nano interface even at equilibrium, and that the dominant cause of the drift is diffusophoresis.