Superparamagnetic micro-bead chains and microswimmers under the influence of an oscillating magnetic field are studied experimentally and numerically. The numerical scheme composed of the lattice Boltzmann method, immersed boundary method, and discrete particle method based on the simplified Stokesian dynamics is applied to thoroughly understand the interaction between the micro-bead chain (or swimmer), the oscillating magnetic field, and the hydrodynamics drag. The systematic experiments and simulations demonstrated the behaviors of the microchains and microswimmers as well as the propulsive efficiencies of the swimmers. The effects of key parameters, such as field strengths, frequency, and the lengths of swimmer, are thoroughly analyzed. The numerical results are compared with the experiments and show good qualitative agreements. Our results proposed an efficient method to predict the motions of the reversible magnetic microdevices which may have extremely valuable applications in biotechnology.

ABSTRACT:Thin organic polymer films were prepared by plasma polymerization in the heated system. The films obtained were very smooth and free of pinholes. The electrical conductivities ranged from 10-6 to 10-7 Scm-1 and the AliPolymeriAu cells with polymers produced from fumaronitrile and p-aminobenzonitrile showed rectifying effect. Both IR observations and electrical measurements confirmed that the conjugated double bonds formed by plasma polymerization in the heated system were responsible for high electrical conductivity. The plot of log u vs. 1IT gave straight line and 0.29 eV of the activation energy was determined for fumaronitrile polymer.

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A new atomization process for making metal powders is presented, in which molten metal is ejected into water layer formed on a rotating drum inner surface by the centrifugal force and atomized by the rotating water. Atomization trials were made using Fe4NkoB20 alloy. A mean particle size of the powder obtained decreased with increasing rotational speed of the drum and with decreasing nozzle diameter. The quench rate for particles less than about 100um in diameter was estimated to range from 105 to 106 K/s, and spherical amorphous powder was obtained. This process may be useful for producing rapidly quenched metallic powders because of its high quench rate, uniform size and spherical shape of powders produced, high powder yield and no scattering of particles.

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