School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, Guangdong 510640, China.
Nanoscale. 2014 Apr 7;6(7):3686-94. doi: 10.1039/c3nr06238d.
Control of mass transport through nanochannels is of critical importance in many nanoscale devices and nanofiltration membranes. The gates in biological channels, which control the transport of substances across cell membranes, can provide inspiration for this purpose. Gates in many biological channels are formed by a constriction ringed with hydrophobic residues which can prevent ion conduction even when they are not completely physically occluded. In this work, we use molecular dynamics simulations to design a nanogate inspired by this hydrophobic gating mechanism. Deforming a carbon nanotube (12,12) with an external force can form a hydrophobic constriction in the centre of the tube that controls ion conduction. The simulation results show that increasing the magnitude of the applied force narrows the constriction and lowers the fluxes of K(+) and Cl(-) found under an electric field. With the exerted force larger than 5 nN, the constriction blocks the conduction of K(+) and Cl(-) due to partial dehydration while allowing for a noticeable water flux. Ion conduction can revert back to the unperturbed level upon force retraction, suggesting the reversibility of the nanogate. The force can be exerted by available experimental facilities, such as atomic force microscope (AFM) tips. It is found that partial dehydration in a continuous water-filled hydrophobic constriction is enough to close the channel, while full dewetting is not necessarily required. This mechanically deformed nanogate has many potential applications, such as a valve in nanofluidic systems to reversibly control ion conduction and a high-performance nanomachine for desalination and water treatment.
控制纳米通道中的物质传输对于许多纳米尺度设备和纳滤膜至关重要。生物通道中的门控结构可以控制物质跨细胞膜的传输，为实现这一目标提供了灵感。许多生物通道中的门由带有疏水性残基的环所构成，即使不完全物理阻塞也可以阻止离子传导。在这项工作中，我们使用分子动力学模拟设计了一种受这种疏水性门控机制启发的纳米门。通过外部力对碳纳米管（12,12）进行变形可以在管的中心形成一个疏水的紧缩区，从而控制离子传导。模拟结果表明，增加所施加力的大小可以缩小紧缩区并降低电场下 K(+)和 Cl(-)的通量。当所施加的力大于 5 nN 时，由于部分去水作用，紧缩区会阻止 K(+)和 Cl(-)的传导，但仍允许可观的水流通过。当力缩回时，离子传导可以恢复到未受扰的水平，这表明纳米门是可恢复的。这种力可以通过现有的实验设备施加，例如原子力显微镜（AFM）针尖。研究发现，在连续充满水的疏水区段中进行部分去水足以关闭通道，而不一定需要完全去湿。这种机械变形的纳米门具有许多潜在的应用，例如在纳米流控系统中作为一种用于可逆控制离子传导的阀，以及用于海水淡化和水处理的高性能纳米机器。
