Generation of mechanical force by grafted polyelectrolytes in an electric field. Application to polyelectrolyte-based nano-devices

We analyze 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 favors its adsorption on the plane. The free end of the chain is linked to a deformable target body. 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 arising in the body force. Our theoretical predictions for the generated force are in a very good agreement with the MD data. Using the developed theory for the generated force we study the effectiveness of possible PE-based nano-vices, comprised of two clenching planes connected by PEs and exposed to an external electric field. We exploit Cundall-Struck solid friction model to describe the friction between a particle and the clenching planes. We compute the self-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 a possible alternative to the existing nano-tube nano-tweezers and optical tweezers.
Comment: Accepted for publication in Philosofical Transactions A