Electrophoretic and dielectrophoretic trapping of molecular objects in planar quadrupole electrode configuration at room temperature

Abstract

Recent rapid development of single molecule analysis highly demands the trapping of molecular objects. In this study, we present how stability and random motions vary depending on dielectrophoretic and electrophoretic descriptions for a molecular object in planar quadrupole electrical traps. The object is modeled as a molecular dipole surrounded by a cavity ("molecular dipole cavity") to introduce the solvent accessible surface of a solute molecule, and the instantaneous electrophoretic and dielectrophoretic force formulations are employed for the rigorous estimation of the deterministic stability which is identified by the equation of motion without random impulse and the random fluctuation that is compared with the trap size for the identification of random stability. The deterministic stability is analyzed with the universal Mathieu equation based theories for Paul trap while the random fluctuation is computed by averaging the multiple trajectories with different random seeds. The results show that the deterministic stabilities are quite similar in dielectrophoretic and electrophoretic descriptions, whereas the random fluctuation is significantly influenced by the type of force description. This study is expected to provide fundamental information in designing a quadrupole trap for molecular objects which is essential in single molecule analysis.