Scientific Reports 3, Article number: 3483 (2013); Published: 19 December 2013; Updated: 31 October 2014

The original version of this Article contained a typographical error in the Results section.

Under the subheading ‘Theoretical analysis of electrical forces’, “and ζp and up are the dynamic viscosity and particle velocity, respectively” should read “and ζp and up are the surface potential and the velocity of the particle, respectively”.