Molecular-level evaluation of ionic transport under external electric fields in biological dielectric liquids.

• Drift velocities of ions increase nonlinearly under external electric fields. • Scattering determines the threshold of the ion drift. • Structural cages limit the ion drift effectively under lower electric field strength. • Electric motion replaces thermal motion under higher electric field strength. • Biological liquids facilitate the restriction of cationic electric drifts. Ionic conduction is a critical parameter to evaluate the electrical performance of biological dielectric liquids. In this work, detailed molecular dynamics (MD) simulations were carried out to reveal both drift mechanisms of ions (H 3 O+, Cu2+, OH– and Cl-) and local structure evolution characteristics in biological dielectric liquids under external electric fields. The drift velocities of all ionic species increase nonlinearly with the addition of static electric fields. At relatively low field regimes, the structural cages formed by corresponding biological dielectric molecules are found to reduce ion transport. Above certain field thresholds, the accelerated ions impart appreciable energy to the surrounding molecular segments, making the binding of the cages broken. As such, the electric motion as a replacement of the thermal motion is eventually taken place. The computed thresholds are 0.97 V/nm, 0.645 V/nm, 0.67 V/nm, and 0.77 V/nm for H 3 O+, Cu2+, OH–, and Cl-, respectively. Additionally, given the electrostatic potential feature of biological dielectric molecules, the structural cages have greater advantages in limiting cationic migration, in which the binding effect for cations is more stable and persistent. The results provide a helpful guideline for designing the next-generation biological dielectric liquids. [ABSTRACT FROM AUTHOR]