Synthesis and characterization of hydrophobised magnetite nanoparticles for production of liquid marbles and modeling of liquid marble deformation under the gravity effect

Liquid marbles are emerging discrete droplet microfluidic systems that are a simple alternative to conventional droplet microfluids encapsulated by hydrophobic nanoparticles or micro-particles. One of the most important applications of liquid marbles is their use in biochemistry, biomedicine, nanotechnology and so on. In this research, liquid marbles are studied in two parts of practical and simulation. In the practical part, for the production of liquid marbles, magnetite nanoparticles are first synthesized and hydrophobised with paraffin wax. In the next step, using a micropipette, a droplet of water is placed on the nanoparticles and by tilting the surface, it is rolled on the nanoparticles, which finally forms a "liquid marble". Finally, the opening and closing of the powdery shell studied using a magnetic field induced by a fixed magnet. In the simulation section, by modelling the marble with an elastic shell around the droplet, the effect of the gravitational force on it, was examined and it was observed that the simulation results show well agreement with the practical part

Microseparator based-on 4-phase travelling wave dielectrophoresis for lab-on-a-chip applications

506-515Separation of micron-sized particles is a challenge by highly miniaturized channel systems. In order to offer the ability of smaller volumes and high throughput in Lab-on-a-chip devices more miniaturized components are needed. Due to very low Reynolds number of buffer fluid, microseparators based on travelling wave dielectrophoresis effect have a good efficiency in such applications. In the present paper, a microchannel technique based on surface micromachining is modified to a microseparator. The proposed device is a miniaturized 4-phase travelling wave microseparator with the height of 5 µm, which can be used for separation of biological particles such as cells and some types of viruses. According to numerical simulations, the device can separate and sort different species, as well as different sized cells of the same species. Due to fabrication process, the electrodes made of highly doped poly-silicon are covered by a thin silicon-nitride layer. Additional advantage of the silicon-nitride layer over electrode arrays is the prevention of high electric field gradient. The effect of this thin insulating layer on functionality of the microseparator has been investigated. The simulation results show that a good separation occurs in the frequency range of 1MHz, when electrical conductivity of buffer fluid is near 1μs/m. The fabrication process is presented and influences of other parameters such as permittivity of fluid and fluid conductivity on the operation of the separator are discussed