title: Theoretical investigation of bacteria polarizability under direct current electric fields.
abstract: We present a theoretical model to investigate the influence of soft polyelectrolyte layers on bacteria polarizability. We resolve soft-layer electrokinetics by considering the pH-dependent dissociation of ionogenic groups and specific interactions of ionogenic groups with the bulk electrolyte to go beyond approximating soft-layer electrokinetics as surface conduction. We model the electrokinetics around a soft particle by modified Poisson-Nernst-Planck equations (PNP) to account for the effects of ion transport in the soft layer and electric double layer. Fluid flow is modeled by modified Stokes equations accounting for soft-layer permeability. Two test cases are presented to demonstrate our model: fibrillated and unfibrillated Streptococcus salivarius bacteria. We show that electrolytic and pH conditions significantly influence the extent of soft-particle polarizability in dc fields. Comparison with an approximate analytical model based on Dukhin-Shilov theory for soft particles shows the importance of resolving soft-layer electrokinetics. Insights from this study can be useful in understanding the parameters that influence soft-particle dielectrophoresis in lab-on-a-chip devices.
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Naga Neehar
authors.initials: NN
authors.lastname: Dingari
authors.forename: Cullen R
authors.initials: CR
authors.lastname: Buie
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D018407:Bacterial Physiological Phenomena; D004560:Electricity; D004573:Electrolytes; D008962:Models, Theoretical; D013291:Streptococcus / Q000378:metabolism
chemical_list: D004573:Electrolytes