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

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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.