Electro-Orientation and Electro-Rotation of Metallodielectric Janus Particles

The electro-rotation (EROT) and electro-orientation (EOR) behavior of metallodielectric 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 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's angular velocity on the forcing frequency of a rotating and nonrotating spatially uniform electric field, respectively, are explicitly determined and compared against experiments (different JP sizes and solution conductivities). While a favorably good agreement between theory and experimental measurements was found for the frequency response (similar to 8% difference), there is still a factor of similar to 2 difference in the amplitude of the angular velocity, which necessitates further future improvements to the model.

Automated summary

The electro-rotation and electro-orientation behavior of metallodielectric spherical Janus particles are studied analytically and experimentally. Analytic expressions for the dipole terms of the Janus particles are obtained, and the EROT and EOR spectra are determined and compared against experiments. Although a good agreement is found in the frequency response, further improvements are needed to address the discrepancy in the amplitude of the angular velocity.