arXiv subjects

Daniel Sofer

Publications and source records attributed to Daniel Sofer.

2 recordsLinked to original sources

arXiv2022

Electro-Orientation and Electro-Rotation of Metallodielectric Janus Particles

The electro-rotation (EROT) and electro-orientation (EOR) behavior of metallodielectric (MD) spherical Janus particles (JP) are studied analytically and verified experimentally. This stands in contrast to previous either heuristic or numerically computed models of JP dipoles. First, we obtain frequency-dependent analytic expressions for the corresponding dipole terms for a JP composed of a dielectric and metallic hemispheres, by applying the standard (weak-field) electrokinetic model and using a Fourier-Legendre collocation method for solving two sets of linear equations. EROT and EOR spectra, describing the variation of the JP angular velocity on the forcing frequency of a rotating and non-rotating spatially uniform electric field, respectively, are explicitly determined and compared against experiments (different JP size and solution conductivity). A favorably good qualitative agreement between theory and experimental measurements was found.

physics.flu-dyn↗

arXiv2022

Optically Modulated Propulsion of Electric Field Powered Photoconducting Janus Particles

Herein we demonstrate the ability to optically tune the mobility of electrically powered Janus particles (JP) that are half coated with various Zinc Oxide (ZnO) semiconducting layers, i.e. polycrystalline, amorphous and amorphous with a SiO2 passivation layer. The ZnO semiconductor photo-response enables increase in its electrical conductivity with light having wavelengths of sufficient photon energy with respect to the semiconductor bandgap. This effect, termed optically modulated electrokinetic propulsion (OMEP), can be harnessed to increase the contrast in polarizability between the dielectric and semiconducting hemispheres, which in turn, results in an increased electrokinetic mobility. The addition of optical activation to the electrical field enables an additional degree of control of JP mobility. We also demonstrate optical control of collective behavior and particle-particle interactions for dense semi-conducting Janus particle populations.

cond-mat.mtrl-sci↗