the possible consequences of this latter type of particle-based measurements. We address theoretically a prototypical pressure-driven flow experiment in small channels in the case where small tracer particles are used to probe the fluid velocity. We show that if electrical effects for both the channel and the particles are properly taken into account, it is possible for the particles to behave as if they were advected by a flow with a finite non-zero slip length, even if the velocity profile in the fluid surrounding the particle does not violate the no-slip condition.

In the following section we summarize some important background electrostatics and hydrodynamics results, derive the formulae in the case of two dimensional channels and introduce the electroviscous effect. In section \[suspended\] we present a physical picture for the effect we report, derive the expressions for the apparent slip lengths and give the conditions for the occurrence of such slip. Finally, in section \[discussion\] we discuss implications of these results along with estimates of their order of magnitude under typical experimental conditions and compare with experiments.

Flow of an electrolyte solution {#physical}
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The physical picture for the effect we wish to introduce relies on the following known facts.

