Preparative fractionation of single walled carbon nanotubes in microfluidic channels by means of combined centrifugal and electrical separative forces

单壁碳纳米管由一个石墨烯薄片卷成一个无缝圆柱体组成。有两种单壁碳纳米管需要区分：金属和半导体。为了实现基于纳米管的电子学，需要分别操纵金属纳米管和半导体纳米管。不幸的是，金属和半导体纳米管通常生长在一起，合成时会产生半导体和金属管的混合物。在这种背景下，金属纳米管和半导体纳米管的分离成为现实。目前最成熟的纳米管悬浮液分离方法是微流控技术和介电泳法。微流控技术是基于微流控流道中的层流流动，由于流动条件不对称，微流控流道发生分离。在介电方面，金属管和半导体管相对于溶剂的相对介电常数的不同导致沿电场梯度作用于金属管和半导体管的反作用力。在外加电场的作用下，金属纳米管可以沉积在浮动微电极上。然而，对于大多数用途，微流控和介电泳法的吞吐速率都需要扩大。该项目的目的是通过分离纳米管来提高生产率。作用在金属纳米管和金属微粒之间的正介电泳力完成了这一任务。施加在电池电极上的电场会在金属微粒周围产生不均匀的电场，这些微粒在溶剂中自由移动。在这个不均匀的磁场中，金属管与金属微粒排列在一起，并与这些载体粒子一起运动。由于离心场中的沉淀作用，金属颗粒在无电场的情况下达到了晶胞区域，金属纳米管脱离了载流子颗粒。通过这种方式，金属纳米管的收集发生在微流控电池的一侧。由于流动条件的不对称，半导体纳米管在溶剂中保持自由状态，并向微流控电池的另一侧移动。金属载体的应用大大提高了微流控电池的有效体积，具有较高的沉积速率。这执行增强的分离吞吐速率。单电池的设计必须进行优化。这需要选择最佳的工艺参数，如悬浮液的流量、纳米管的浓度、外加电场的幅度和频率。分离结果将通过不同的光谱技术进行测试。将对微流控电池中发生的过程进行模拟。介观水平可以通过几个单独的微流体单元并联连接来实现。

Single-walled carbon nanotubes consist of a single graphene sheet rolled up into a seamless cylinder. There are two kinds of single-walled carbon nanotubes to distinguish: metallic and semiconducting. For the realization of nanotube-based electronics, it is necessary to manipulate metallic and semiconducting nanotubes separately. Unfortunately, metallic and semiconducting nanotubes typically grown together and synthesis produce a mix of semiconducting and metallic tubes. In this context, the separation of metallic and semiconducting nanotubes becomes actuality. The most developed separation methods of nanotubes in suspension used the microfluidic and dielectrophoresis techniques. Microfluidics technique is based on a laminar flow in microfluidic channels where due to asymmetric flow conditions occurs the separation. In terms of dielectrophoresis the difference of the relative dielectric constants of metallic and semiconducting tubes with respect to the solvent results in an opposite force acting on metallic and semiconducting tubes along the electric field gradient. Inside an applied electrical field dielectrophoresis enables the deposition of metallic nanotubes at the floating microelectrodes. However, the throughput rate of both microfluidic and dielectrophoresis techniques need to be scaled up for most uses. The aim of the project is increasing the throughput rate by separation of nanotubes. The positive dielectrophoresis force acting between metallic nanotubes and metallic micro particles performs this task. The electrical field applied to cell electrodes induces the inhomogeneous electrical field around metallic micro particles that are free moving in solvent. In this inhomogeneous field, the metallic tubes aligned with metallic micro particles and move together with these carrier particles. Due to sedimentation in centrifugal field the metallic particles achieve the cell region without electrical field, where metallic nanotubes become free from carrier particles. In this way the collection of metallic nanotubes occurs at one side of microfluidic cell. The semiconducting nanotubes remain free in solvent and move to the other side of microfluidic cell due to asymmetric flow conditions. The application of metallic parties as carrier with high sedimentation rate increases the effective volume of microfluidic cell significantly. This performs the enhanced throughput rate of separation. The design of single cell has to be optimized. This needs the selection of optimal process parameters such as flow rate of suspension, concentration of nanotubes, amplitude and frequency of applied electrical field. The results of separation will be tested by means of different spectroscopic techniques. The simulation of processes occurring in microfluidic cells will be carried out. The mesoscopic level can be achieved by means of connection of several individual microfluidic cells in parallel.