Non-ponderomotive stability and random motion in micro-/nano-scale quadrupole dielectrophoretic traps

Abstract

Quadrupole dielectrophoretic traps are widely used for the confinement of biological objects in various applications. This study shows the non-ponderomotive stability and random motion of micro-/nano-scale quadrupole dielectrophoretic traps. Distinguished from Paul traps, dielectrophoretic traps are unusually stable to the change of medium viscosity and it can be explained with the robustness of the stability island. Also, the present non-ponderomotive approach enables quantification of the random fluctuation rigorously ranging from the micro-to nanoscale. The pseudo-potential prediction works only when both the trap and particle are in the same lengthscale. Since the random motion determines the size of the virtual pore formed inside the trap, the magnitude of random fluctuation is a key parameter in trap optimization. In this study, the trap size and the oscillating frequency are adjusted to localize a particle within the nanometre area at the trap center. This paper provides an efficient method to optimize the essential factors in the design of nanoscale dielectrophoretic traps.