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Bipolar Janus particle assembly in microdevice
Author(s) -
Hossan Mohammad R.,
Gopmandal Partha P.,
Dillon Robert,
Dutta Prashanta
Publication year - 2015
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201400423
Subject(s) - electric field , particle (ecology) , mechanics , janus , janus particles , physics , classical mechanics , maxwell stress tensor , materials science , cauchy stress tensor , nanotechnology , oceanography , quantum mechanics , geology
In recent years, there are significant interests in the manipulation of bipolar Janus particles. In this article, we investigate the transient behavior of the electro‐orientation process and particle–particle interaction of ellipsoidal bipolar Janus particles in the presence and absence of a DC electric field. The bipolar particle dynamics is modeled with a body force term in the fluid flow equations based on the Maxwell stress tensor. This force is due to presence of bipolar surface charges on the particles as well as their interactions with an imposed field. An interface resolved numerical scheme that consider the finite size of the particle is adopted for computation of the electric and flow fields. Our numerical results show that in the absence of an electric field, particles can undergo self‐orientation to reach an equilibrium position. The time taken to reach a stable orientation depends on the initial configuration and inter‐particle separation distance. Bipolar particles experience forces only on their polar ends, a phenomena that is difficult to capture with noninterface resolved methods. When bipolar particles are exposed to an external electric field, they rotate to align along the external electric field direction. Depending upon the initial configuration, particles orient via clockwise or counter clockwise rotations to form head to tail chains. The time required to form particle assembly strongly depends on particle size and bipolar charge density. The present numerical algorithm can be applied to a wider class of dual‐faced Janus particles.