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

单壁碳纳米管由单层石墨烯片卷成无缝圆柱体组成。单壁碳纳米管分为两种：金属碳纳米管和半导体碳纳米管。为了实现基于纳米管的电子学，有必要分别操作金属纳米管和半导体纳米管。不幸的是，金属纳米管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纳米管的混合物。在此背景下，金属纳米管与半导体纳米管的分离成为现实。微流控技术和介电泳技术是目前发展最快的纳米管悬浮液分离方法。微流控技术是基于微流控通道内的层流，其中由于流动条件的不对称而发生分离。在电介质电泳方面，金属管和半导体管相对于溶剂的介电常数的差异导致沿电场梯度作用在金属管和半导体管上的力相反。在外加电场中，介质电泳可以使金属纳米管沉积在漂浮的微电极上。然而，微流体和介电泳技术的通量在大多数应用中都需要扩大。该项目的目的是通过分离纳米管来提高吞吐率。作用于金属纳米管和金属微粒之间的正电导力完成了这项任务。施加在电池电极上的电场在溶剂中自由运动的金属微粒周围产生非均匀电场。在这个非均匀场中，金属管与金属微粒排成一列，并与这些载体粒子一起运动。由于在离心力场中的沉降作用，金属颗粒到达了没有电场的胞区，在那里金属纳米管不受载体颗粒的影响。通过这种方式，金属纳米管聚集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，并向微流控电池的另一侧移动。采用高沉降速率的金属微粒作为载体，显著提高了微流控电池的有效体积。这提高了分离的吞吐率。单细胞的设计需要优化。这需要选择最佳的工艺参数，如悬浮液流速、纳米管浓度、外加电场的振幅和频率。分离结果将通过不同的光谱技术进行测试。将进行微流体电池过程的模拟。介观水平可以通过并联几个单独的微流控细胞来实现。

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.