Oyarzua Elton, Walther Jens H, Zambrano Harvey A
Department of Computing Technologies, Swinburne University of Technology, P.O. Box 218 Hawthorn, Victoria 3122, Australia.
Department of Civil and Mechanical Engineering, Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark.
Phys Chem Chem Phys. 2023 Feb 8;25(6):5073-5081. doi: 10.1039/d2cp04093j.
Accurate control of fluid transport in nanoscale structures is key to enable the design of foreseeable nanofluidic devices with applications in many fields such as chip cooling, energy conversion, drug delivery and medical diagnosis. Here, inspired by the experimental observation of intrinsic thermal ripples in graphene and by recent advances in the manipulation of 2D nanomaterials, we introduce a graphene-based thermal nanopump which produces controlled and continuous liquid flow in nanoslit channels. We investigate the performance of this thermal nanopump employing large scale molecular dynamics simulations. Upon systematically imposing thermal gradients, a net water flow towards the low-temperature zone is observed, achieving flow velocities up to 4 m s. We observe that water flow rates increase monotonically due to larger ripple fluctuations on the graphene layers as higher thermal gradients are applied. Moreover, we find that the out-of-plane flexural phonons in graphene are responsible for flow generation wherein lower frequency phonon branches are activated with higher imposed thermal gradients. Furthermore, by modifying the wettability of the channel walls, an increase of 50% in the water flow rates is observed, showing that the efficiency of the proposed thermal pump can be enhanced by tuning the channel wall hydrophobicity. Our results indicate that thermal gradients can be employed to drive continuous water flow in graphene nanoslit channels with potential applications in nanofluidic devices.
精确控制纳米级结构中的流体传输是设计具有可预见应用的纳米流体装置的关键，这些装置可应用于芯片冷却、能量转换、药物输送和医学诊断等许多领域。在此，受石墨烯中固有热波动的实验观察以及二维纳米材料操纵方面最新进展的启发，我们引入了一种基于石墨烯的热纳米泵，它能在纳米狭缝通道中产生可控且连续的液体流动。我们采用大规模分子动力学模拟来研究这种热纳米泵的性能。在系统地施加热梯度后，观察到水向低温区的净流动，流速可达4 m/s。我们发现，随着施加的热梯度增加，由于石墨烯层上更大的波动起伏，水的流速单调增加。此外，我们发现石墨烯中的面外弯曲声子是产生流动的原因，其中较低频率的声子分支随着更高的热梯度施加而被激活。此外，通过改变通道壁的润湿性，观察到水流速增加了50%，这表明通过调节通道壁的疏水性可以提高所提出的热泵的效率。我们的结果表明，热梯度可用于驱动石墨烯纳米狭缝通道中的连续水流，在纳米流体装置中具有潜在应用。
