Particle-localized AC and DC manipulation and electrokinetics

摘要

Colloidal particles suspended in water respond to direct (DC) or alternatingncurrent (AC) fields in a variety of ways, including directional motion alongnor across the field direction, field-gradient dependent response and inducednparticle–particle interaction. We review here some of these effects and theirnapplications in new techniques for particle manipulation and assembly,nmaking of novel biomaterials and designing of new self-propelling microdevices.nThe coupling of the counterionic layer mobility, fluid flows and thenresulting particle motion are the basis not only of the classic electrophoreticneffects, but also of the recent developments in AC electrohydrodynamicsnand induced charge electrophoresis of asymmetric particles. We also discussnhow dielectrophoresis (particle interaction with external AC field gradients),ncould be used to manipulate and assemble objects on any size scale. Wendiscuss the interactions leading to the assembly of such structures, ways tonsimulate the dynamics of the process and the effect of particle size andnconductivity on the type of structure obtained. Finally, we demonstrate hownan additional level of complexity can be engineered to turn miniaturensemiconductor diodes into prototypes of self-propelling micromachinesnand micropumps. The diodes suspended in water propel themselvesnelectro-osmotically when a uniform alternating electric field is appliednacross the container. Semiconductor diodes embedded in channel wallsncould serve as distributed microfluidic pumps and mixers powered by anglobal external field.