Theory for hierarchical assembly with dielectrophoresis and the role of particle anisotropy

Abstract

Nonuniform electric fields cause polarizable particles to move through an effect known as dielectrophoresis (DEP). Additionally, the particles themselves create nonuniform fields due to their induced dipoles. When the nonuniform field of one particle causes another to move, it represents a path to hierarchical assembly termed mutual DEP (mDEP). Anisotropic particles potentially provide further opportunities for assembly through intense and intricate local field profiles. Here, we construct a theoretical framework for describing anisotropic particles as templates for assembly through mDEP by considering the motion of small nanoparticles near larger anisotropic nanoparticles. Using finite element analysis, we study eight particle shapes and compute their field enhancement and polarizability in an orientation‐specific manner. Strikingly, we find a more than tenfold enhancement in the field near certain particle shapes, potentially promoting mDEP. To more directly relate the field intensity to the anticipated assembly outcome, we compute the volume experiencing each field enhancement versus particle shape and orientation. Finally, we provide a framework for predicting how mixtures of two distinct particle species will begin to assemble in a manner that allows for the identification of conditions that kinetically bias assembly toward specific hierarchical outcomes.

Electric field induced macroscopic cellular phase of nanoparticles

“…S11(b) (ESI†) shows that many of the cluster phases were co-localized with the centers of the voids of the cellular phase. Together, these results suggest that features of the underlying substrate, likely asperities on the surface of the electrode, can enhance local electric field, 28 break the symmetry of the system and nucleate the phase transition. The hypothesized nucleation of the phase transformation at the regions of high field on the substrate explains the repeatable arrangement of cells that were observed when the experiment was repeated as in Fig.…”

Direct pumping of polar fluids with traveling‐wave dielectrophoresis

“…In addition to the Columbic force on charged species, dielectrophoresis (DEP) is the motion of polarizable materials in nonuniform electric fields [19][20][21][22][23][24]. Although conventional DEP is a restorative effect and cannot result in net pumping, the use of traveling wave effects through traveling-wave DEP (twDEP) can lead to pumping when the polarizable species has an imaginary component of its polarizability.…”