Abstract
We analyse theoretically and by means of molecular dynamics (MD) simulations the generation of mechanical force by a polyelectrolyte (PE) chain grafted to a plane. The PE is exposed to an external electric field that favours its adsorption on the plane. The free end of the chain is linked to a deformable target body. By varying the field, one can alter the length of the non-adsorbed part of the chain. This entails variation of the deformation of the target body and hence variation of the force arising in the body. Our theoretical predictions for the generated force are in very good agreement with the MD data. Using the theory developed for the generated force, we study the effectiveness of possible PE-based nano-vices, composed of two clenching planes connected by PEs and exposed to an external electric field. We exploit the Cundall-Strack solid friction model to describe the friction between a particle and the clenching planes. We compute the diffusion coefficient of a clenched particle and show that it drastically decreases even in weak applied fields. This demonstrates the efficacy of the PE-based nano-vices, which may be a possible alternative to the existing nanotube nano-tweezers and optical tweezers.This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.
Highlights
Future nanotechnology will use molecular devices executing various manipulations with nano-size objects, such as colloidal particles, vesicles, macromolecules, viruses, small bacteria, cell organelles, etc
The dependence of the field-induced force acting on the target body is shown as a function of the external electric field
We investigate the generation of a mechanical force by a PE chain grafted to a plane and exposed to an external electric field, when it is linked to a deformable target body
Summary
Future nanotechnology will use molecular devices executing various manipulations with nano-size objects, such as colloidal particles, vesicles, macromolecules, viruses, small bacteria, cell organelles, etc. One needs (i) to develop a theory of a conformational response of a PE, with one end linked (grafted) to a charged surface and the other one to a deformable target body, and exposed to a varying electric field, and (ii) to quantify the ability of nano-vices to clench a nano-size object. One obtains the dependence on applied field of the force that arises between the chain and the target body This may be done by minimizing the total free energy of the system F(N, ztop, R) = Fch(N, ztop, R) + Fcount(ztop) with respect to N, ztop and R and using Ns = N0 − N and the constraint ztop ≤ bN.
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