Electrorotation and levitation of cells and colloidal particles

Abstract

We review dielectrophoretic forces on cells and colloidal particles, emphasizing their use for manipulating and characterizing the electrical properties of suspended particles. Compared with dielectric spectroscopy, these methods offer a measure of independence from electrode artifacts and mixture theory. On the assumption that the particles can be modeled as uniform dielectric objects with effective dielectric properties, a simple theory can be developed for the frequency variation in the field-induced forces. For particles exhibiting counterion polarization, dielectrophoretic forces differ considerably from predictions of this theory at low frequencies, apparently because of double layer phenomena.

Automated electrorotation shows electrokinetic separation of pancreatic cancer cells is robust to acquired chemotherapy resistance, serum starvation, and EMT

“…Most spectra consist of two relaxations that appear as a peak and a trough: (1) a low frequency ($10 5 Hz) peak dominated by the cell radius, specific membrane capacitance, and suspending medium conductivity, and (2) high-frequency ($10 6 -10 8 Hz) trough associated with DEP transitioning from being dominated by the cell-medium conductivity mismatch to the cellmedium permittivity mismatch. 40 The effect of acquired resistance to gemcitabine on BxPC3 pancreatic cancer cell sub-clones appears in Figure 6. Most notably for the design of future DEP devices, the calculated crossover frequency significantly decreased for both gemcitabine-resistant sub-clones as compared to gemcitabine-na€ ıve parental BxPC3s (p < 0.05, Wilcoxon rank sum test), effectively widening the frequency window at which a majority of cancer cells experience pDEP and a majority of white blood cells (WBCs) experience nDEP.…”

Magnetically controlled dielectrophoresis of metallic colloids

“…(2) for the equilibrium position of the nanowire (angle θ ) and the angular velocity (θ ), the last parameter being responsible for the appropriate choice of the time interval t. It is elementary to find that Eq. (2) may be written in the forṁ θ = a sin θ + b cos θ + c sin 2 θ + d cos 2 θ + e sin θ cos θ, (14) where…”

“…In the absence of any applied magnetic field H x = H y = 0s o that a = b = 0 and Eq. (14) reduces to an electrorotation problem. The absence of any applied electric field will give c = d = e = 0 and we have a pure magnetorotation of the nanowires.…”

“…Equations (1) and (2) are simultaneously solved and both position and orientation of the nanowire updated according to Eqs. (12), (13), and (14).T h i ss t r a t e g yi sa p p l i e df o re a c ht y p e of nanowire in Table 1 and different degrees of freedom. In a first simulation we considered completely free nanowires; that is, they are moving in the absence on any applied magnetic field.…”

“…Several experimental and theoretical works demonstrated that the basic theory of DEP and electrorotation [1,13,14] may successfully be applied to predict full trajectories [15] or equilibrium configurations (chaining) [16] of spherical dielectric beads. For particles of arbitrary shapes, analytical multipolar approaches [17] and numerical strategies [18] have already been proposed.…”