Exact axisymmetric interaction of phoretically active Janus particles

We study the axisymmetric interaction of two chemically active Janus particles. By relying on the linearity of the field equations and symmetry arguments, we derive a generic solution for the relative velocity of the particles. We show that regardless of the chemical properties of the system, the relative velocity can be written as a linear summation of geometrical functions which only depend on the gap size between the particles. We evaluate these functions via an exact approach which accounts for the full chemical and hydrodynamic interactions. Using the obtained solution, we expose the role of each compartment in the relative motion, and also discuss the contribution of different interactions. We then show that the dynamical system describing the relative motion of two Janus particles can have up to three fixed points. These fixed points can be stable or unstable, indicating that a system of two Janus particles can exhibit a variety of nontrivial behaviour depending on their initial gap size, and their chemical properties. We also look at the specific case of Janus particles in which one compartment is inert, and present regime diagrams for their relative behaviour in the activity-mobility parameter space

Efficiency limits of the three-sphere swimmer

We consider a swimmer consisting of a collinear assembly of three spheres connected by two slender rods. This swimmer can propel itself forward by varying the lengths of the rods in a way that is not invariant under time reversal. Although any non-reciprocal strokes of the arms can lead to a net displacement, the energetic efficiency of the swimmer is strongly dependent on the details and sequences of these strokes, and also the sizes of the spheres. We define the efficiency of the swimmer using Lighthill's criterion, i.e., the power that is needed to pull the swimmer by an external force at a certain speed, divided by the power needed for active swimming with the same average speed. Here, we determine numerically the optimal stroke sequences and the optimal size ratio of the spheres, while limiting the maximum extension of the rods. Our calculation takes into account both far-field and near-field hydrodynamic interactions. We show that, surprisingly, the three-sphere swimmer with unequal spheres can be more efficient than the equally-sized case. We also show that the variations of efficiency with size ratio is not monotonic and there exists a specific size ratio at which the swimmer has the highest efficiency. We find that the swimming efficiency initially rises by increasing the maximum allowable extension of the rods, and then converges to a maximum value. We calculate this upper limit analytically and report the highest value of efficiency that the three-sphere swimmer can reach.Comment: 7 pages, 3 figure

Relationship between Single Walled Carbon Nanotubes Individual Dispersion Behavior and Properties of Electrospun Nanofibers

The dispersion stability behavior of single walled carbon nanotube (SWCNT) has important effects on morphological and mechanical properties of SWCNT/polymer composite nanofibers. The effects of SWCNTs incorporation on the morphological and structural developments and the relation between this develop-ments and mechanical properties of the polyacrylonitrile (PAN) nanofibers were demonstrated. The uni-form, stable dispersion and well oriented SWCNT within the PAN matrix were achieved through using polyvinylpyrrolidone (PVP) as dispersing agent. Our data indicate that with increasing the amount of SWCNT (from 0 to 2 wt %), the average nanofiber diameter was increased from 163±19 nm to 307±34 nm. The analysis of the mechanical properties of the composite nanofibers displays that they exhibit an im-provement in the tensile strength of ∼172% from 3.93±0.45 MPa to 10.74±1.03 MPa, and the elastic modu-lus was increased by ~885% from 61.39±15.58 GPa to 605.08±65.55 GPa, as compared to the pure electro-spun nanofibers. The optimal SWCNT concentration for electrospun nanofibers with better morphological and mechanical properties is ~2 wt %. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3516

A Novel Study of Electrospun Nanofibers Morphology as a Function of Polymer Solution Properties

Electrospinning is a process of production fibers with diameters ranging from the submicron down to the nanometer size by applying a high voltage to a polymer solution. The important parameters in the morphology of electrospun polymer fibers are polymer structure, polymer solution properties, processing conditions, and ambient parameters. In the present work electrospinning of polyacrylonitrile (PAN) has been attempted to generate uniform nanofibers without beads. Electrospinning was performed at various concentrations ranging from 4 to 18 w/v%. The effects of polymer solution properties on electrospinnability of the PAN/DMF solutions have investigated. Fiber morphology was observed under a scanning electron microscopy (SEM). For the polymer electrospun from low concentration (Be4. The relationship between solution viscosity and its concentration is in the form: η 0.0205C4.16 and relation between the diameter of electro-spun the PAN nanofiber and solution concentration is in the form: d 0.0326C3.45. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3514

Fabrication of Homogeneous Multi-Walled Carbon Nanotube/ Poly (Vinyl Alcohol) Composite Nanofibers for Microwave Absorption Application

Poly (vinyl alcohol) (PVA) / sodium dodecyl sulfate (SDS) / multi walled carbon nanotubes (MWCNT) camposite nanofibers with various MWCNT contents (up to 10 wt%) were fabricated by electrospinning process and their microwave absorption properties were evaluated by a vector network analyzer in the frequency range of 8 – 12 GHz (X-band) at room temperature. The uniform, stable dispersion and well oriented MWCNT within the PVA matrix were achieved through using SDS as dispersing agent. The SEM analysis of the nanofibers samples revealed that the deformation of the nanofibers increases with increasing MWCNT concentration. Very smooth surface of the composite electrospun nanofibers even for the nanofibers with concentration of 10 wt MWCNT have been successfully prepared because of the high stability dispersion of MWCNT. It was observed that absorption microwave properties improved with increasing in the loading levels of MWCNT. Finally, the PVA/SDS/MWCNT composite nanofibers sample with the 10 wt content of MWCNT has shown the reflection loss of 15 dB at the frequency of 8 GHz. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3558

A Novel Study of Electrospun Nanofibers Morphology as a Function of Polymer Solution Properties

Electrospinning is a process of production fibers with diameters ranging from the submicron down to the nanometer size by applying a high voltage to a polymer solution. The important parameters in the morphology of electrospun polymer fibers are polymer structure, polymer solution properties, processing conditions, and ambient parameters. In the present work electrospinning of polyacrylonitrile (PAN) has been attempted to generate uniform nanofibers without beads. Electrospinning was performed at various concentrations ranging from 4 to 18 w/v%. The effects of polymer solution properties on electrospinnability of the PAN/DMF solutions have investigated. Fiber morphology was observed under a scanning electron microscopy (SEM). For the polymer electrospun from low concentration (Be4. The relationship between solution viscosity and its concentration is in the form: η 0.0205C4.16 and relation between the diameter of electro-spun the PAN nanofiber and solution concentration is in the form: d 0.0326C3.45. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3514