Nanoporous polycarbonate (PCTE) nuclear-track-etched membranes were us
ed to effect electric field modulation of the mass transport of cation
ic, anionic, and neutral species in aqueous buffer. The permeability r
esponse to electric fields depended on the molecular charge and electr
olyte concentration; Solute and solvent fluxes through nanopores under
an electrical potential result from a balance of diffusion, electroos
mosis, and ion migration The Debye length, kappa(-1), associated with
the electrical double layer within the pores relative to the pore diam
eter, 2a, plays a critical role in determining electrokinetic transpor
t behavior. The channel walls adsorb anions preferentially to produce
a largely immobile negative charge density, leaving a large and mobile
cation population to mediate transport in the channel. By adjusting t
he supporting electrolyte concentration, kappa a can be tuned such tha
t the electrical double layer is either small in relation to the pore
(kappa a greater than or equal to 1) or more diffuse and spanning the
pore (kappa a < 1). Electroosmotic transport, mediated primarily by bu
ffer cations, dominates when kappa a < 1. In this case the pores are e
ssentially permselective, and anion electromigration is virtually elim
inated. When kappa a greater than or equal to 1, the sign of the appli
ed potential can be used to select for anion vs cation/neutral molecul
e transport.