Department of Chemical Engineering, Universidad de Concepcion , Concepcion 4030000, Chile.
Department of Mechanical Engineering, Technical University of Denmark , DK-2800 Kongens Lyngby, Denmark.
ACS Nano. 2017 Oct 24;11(10):9997-10002. doi: 10.1021/acsnano.7b04177. Epub 2017 Sep 29.
Thermal Brownian motors (TBMs) are nanoscale machines that exploit thermal fluctuations to provide useful work. We introduce a TBM-based nanopump which enables continuous water flow through a carbon nanotube (CNT) by imposing an axial thermal gradient along its surface. We impose spatial asymmetry along the CNT by immobilizing certain points on its surface. We study the performance of this molecular motor using molecular dynamics (MD) simulations. From the MD trajectories, we compute the net water flow and the induced velocity profiles for various imposed thermal gradients. We find that spatial asymmetry modifies the vibrational modes of the CNT induced by the thermal gradient, resulting in a net water flow against the thermal gradient. Moreover, the kinetic energy associated with the thermal oscillations rectifies the Brownian motion of the water molecules, driving the flow in a preferred direction. For imposed thermal gradients of 0.5-3.3 K/nm, we observe continuous net flow with average velocities up to 5 m/s inside CNTs with diameters of 0.94, 1.4, and 2.0 nm. The results indicate that the CNT-based asymmetric thermal motor can provide a controllable and robust system for delivery of continuous water flow with potential applications in integrated nanofluidic devices.
热布朗马达（TBMs）是利用热涨落提供有用功的纳米级机器。我们引入了一种基于 TBM 的纳米泵，通过在其表面施加轴向温度梯度，实现连续水流通过碳纳米管（CNT）。我们通过固定 CNT 表面的某些点来施加空间不对称性。我们使用分子动力学（MD）模拟研究了这种分子马达的性能。从 MD 轨迹中，我们计算了在各种施加的温度梯度下的净水流和诱导速度分布。我们发现空间不对称性改变了由温度梯度引起的 CNT 的振动模式，导致净水流与温度梯度相反。此外，与热振荡相关的动能使水分子的布朗运动发生整流，从而沿优选方向驱动流动。对于施加的温度梯度为 0.5-3.3 K/nm，我们观察到在直径为 0.94、1.4 和 2.0nm 的 CNT 内，平均速度高达 5m/s 的连续净流动。结果表明，基于 CNT 的不对称热马达可以提供一种可控且稳健的系统，用于输送连续水流，在集成纳米流控装置中有潜在的应用。
