Berger S D, McGruer N E, Adams G G
MIT Lincoln Laboratory, Lexington, MA, 02421, USA. Department of Mechanical and Industrial Engineering, Northeastern University, Boston, 02115, USA.
Nanotechnology. 2015 Apr 17;26(15):155602. doi: 10.1088/0957-4484/26/15/155602. Epub 2015 Mar 25.
One of the most important methods for selective and repeatable assembly of carbon nanotubes (CNTs) is alternating current dielectrophoresis (DEP). This method has been demonstrated experimentally as a viable technique for nano-scale manufacturing of novel CNT based devices. Previous numerical analyses have studied the motion of nanotubes, the volume from which they are assembled, and the rate of assembly, but have been restricted by various simplifying assumptions. In this paper we present a method for simulating the motion and behavior of CNTs subjected to dielectrophoresis using a three-dimensional electrostatic finite element analysis. By including the CNT in the finite element model, we can accurately predict the effect of the CNT on the electric field and the resulting force distribution across the CNT can be determined. We have used this information to calculate the motion of CNTs assembling onto the electrodes, and show how they tend to move towards the center of an electrode and come into contact at highly skewed angles. Our analysis suggests that the CNTs move to the electrode gap only after initially contacting the electrodes. We have also developed a model of the elastic deformation of CNTs as they approach the electrodes demonstrating how the induced forces can significantly alter the CNT shape during assembly. These results show that the CNT does not behave as a rigid body when in close proximity to the electrodes. In the future this method can be applied to a variety of real electrode geometries on a case-by-case basis and will provide more detailed insight into the specific motion and assembly parameters necessary for effective DEP assembly.
碳纳米管（CNT）选择性和可重复组装的最重要方法之一是交流电介电泳（DEP）。该方法已通过实验证明是一种用于基于新型碳纳米管的器件的纳米级制造的可行技术。先前的数值分析研究了纳米管的运动、它们组装的体积以及组装速率，但受到各种简化假设的限制。在本文中，我们提出了一种使用三维静电有限元分析来模拟碳纳米管在介电泳作用下的运动和行为的方法。通过将碳纳米管纳入有限元模型，我们可以准确预测碳纳米管对电场的影响，并确定碳纳米管上产生的力分布。我们利用这些信息来计算碳纳米管组装到电极上的运动，并展示它们如何倾向于向电极中心移动并以高度倾斜的角度接触。我们的分析表明，碳纳米管仅在最初接触电极后才会移动到电极间隙。我们还建立了一个碳纳米管在接近电极时的弹性变形模型，展示了在组装过程中感应力如何显著改变碳纳米管的形状。这些结果表明，碳纳米管在靠近电极时并不表现为刚体。未来，这种方法可以根据具体情况应用于各种实际电极几何形状，并将更深入地了解有效DEP组装所需的特定运动和组装参数。
