Paris-Sciences Chair Lectures Series

Induced-Charge Electrokinetic Phenomena

Martin Z. Bazant
Department of Mathematics, MIT
ESPCI-PCT

Abstract:  

Microfluidics and nanotechnology have expanded interest in electrokinetics, the study of electrically driven fluid flow past charged surfaces ("electro-osmosis") and the  related motion of charged particles ("electrophoresis"). Electro-osmosis scales favorably with miniaturization, and electrophoresis is convenient for particle manipulation. Classical electrokinetic phenomena are linear in the applied voltage, due to the assumption of fixed surface charge, and this leads to some limitations. For example, electro-osmotic pumps require large DC voltages (> 100 V), and electrophoresis cannot easily separate particles of the same material.

These limitations do not apply to nonlinear, "induced-charge" electrokinetic phenomena involving polarizable surfaces. This lecture series presents the basic physics of induced-charge electro-osmosis and electrophoresis and describes some new applications in microfluidics. Examples include fast (> mm/sec), low-voltage (< 3 V) AC pumps for miniaturized lab-on-a-chip devices and methods for manipulating, separating and assembling polarizable particles. These phenomena also raise fundamental questions about electrokinetics at large applied voltages, which motivate new models for condensed layers of ions.

Lecture 1. Introduction to induced-charge electrokinetics. (Jan 7)
Lecture 2. Electrophoresis of polarizable colloids. (Jan 10)
Lecture 3. AC electro-osmosis in microfluidics. (Jan 17)
Lecture 4. Theory of electrokinetics at large applied voltages. (Feb 14)