Electric-field frictional effects in confined zwitterionic molecules

TL;DR

This paper theoretically investigates how a transverse electric field influences the frictional behavior of confined zwitterionic molecules, revealing controllable transitions between stick-slip and smooth sliding, and demonstrating electric field-induced modulation of friction and thermolubricity.

Contribution

It introduces a theoretical framework showing how electric fields can reversibly control friction in zwitterionic molecular layers, linking molecular orientation to tribological response.

Findings

Electric field induces reorientation of molecular dipoles, affecting sliding dynamics.

Electric field suppresses thermal friction enhancement, restoring thermolubricity.

External load influences friction differently depending on electric field strength.

Abstract

We theoretically explore the effect of a transverse electric field on the frictional response of a bi-layer of packed zwitterionic molecules. The dipole-moment reorientation promoted by the electric field can lead to either stick-slip or smooth sliding dynamics, with average shear stress values varying over a wide range. A structure-property relation is revealed by investigating the array of molecules and their mutual orientation and interlocking. Moreover, the thermal friction enhancement previously observed in these molecules is shown to be suppressed by the electric field, recovering the expected thermolubricity at large-enough fields. The same holds for other basic tribological quantities, such as the external load, which can influence friction in opposite ways depending on the strength of the applied electric field. Our findings open a route for the reversible control of friction forces via electric polarization of the sliding surface.