Self-Generated Electric Fields in Polyelectrolyte Gradients Increase Microparticle Transport

arXiv (Cornell University)

Abstract

There are many situations in nature and industry where small particles are exposed to gradients of charged polymers, such as enzymes in biological gradients of DNA or RNA, virus particles in respiratory droplets, and colloidal particles in stratifying paint layers. Here, we study the phoretic propulsion of charged microparticles in a polyelectrolyte gradient. We theoretically predict the emergence of a macroscopic electric field from charge-separation dynamics in a polyelectrolyte gradient under a continuous diffusive driving force. We confirm the presence of this self-generated electric field experimentally and show that it significantly increases the phoretic velocity of the microparticles. Finally, for high molecular weight polyelectrolytes we observe that propulsion becomes gradient-independent, consistent with diffusiophoretic predictions for asymmetric electrolytes. Our results show that self-generated electric fields in polyelectrolyte gradients can enhance microparticle transport, with potential applicability wherever charged species of different mobility are continuously driven out of equilibrium.

Authors 4

1. Max Huisman Aachen Leiden Institute of Physics (LION)

   Leiden University · University of Applied Sciences Leiden

   Affiliation as printed

   Leiden Institute of Physics (LION) , Leiden University , Niels Bohrweg 2 , 2333 CA Leiden , the Netherlands

2. Ali Azadbakht Aachen Leiden Institute of Physics (LION)

   Leiden University · University of Applied Sciences Leiden

   Affiliation as printed

   Leiden Institute of Physics (LION) , Leiden University , Niels Bohrweg 2 , 2333 CA Leiden , the Netherlands

3. Patrick B. Warren

   Daresbury Laboratory · University of Edinburgh

   Affiliation as printed

   SUPA , School of Physics and Astronomy , University of Edinburgh , Peter Guthrie Tait Road , Edinburgh EH9 3FD , United Kingdom

   The Hartree Centre , STFC Daresbury Laboratory , Warrington WA4 4AD , United Kingdom

4. Daniela J. Kraft Aachen Leiden Institute of Physics (LION)

   Leiden University · University of Applied Sciences Leiden

   Affiliation as printed

   Leiden Institute of Physics (LION) , Leiden University , Niels Bohrweg 2 , 2333 CA Leiden , the Netherlands