Field-regulated force by grafted polyelectrolytes

TL;DR

This study explores how external electric fields can generate controllable mechanical forces in grafted polyelectrolytes, with theoretical and simulation results showing potential applications in nano-manipulation devices.

Contribution

The paper presents a combined theoretical and molecular dynamics approach to quantify electric field-induced forces in grafted polyelectrolytes with various force-deformation behaviors.

Findings

Force magnitude varies widely with electric field.

Theory matches well with simulation results.

No significant difference between zero and finite current cases.

Abstract

Generation of mechanical force regulated by external electric field is studied both theoretically and by molecular dynamics (MD) simulations. The force arises in deformable bodies linked to the free end of a grafted polyelectrolyte chain which is exposed to electric field that favours its adsorption. We consider a few target bodies with different force-deformation relations including (i) linear and (ii) cubic dependences as well as (iii) Hertzian-like force. Such force-deformation relations mimic the behaviour of (i) coiled and (ii) stretched polymer chains, respectively, or (iii) that of a squeezed colloidal particle. The magnitude of the arising force varies over a wide interval although the electric field alters within a relatively narrow range only. The predictions of our theory agree quantitatively well with the results of numerical simulations. Both cases of zero and finite electrical current are investigated and we do not obtain substantial differences in the force generated. The phenomenon studied could possibly be utilised to design, e.g., vice-like devices to fix nano-sized objects.