Multi-step manipulations of PMMA submicron particles using dielectrophoresis.

A microfluidic chip for multi-step manipulations of polymethylmethacrylate submicron particles (PMMA-SMPs) based on dielectrophoresis (DEP) has been developed that includes four main functions of focusing, guiding, trapping and releasing the submicron particles. The structure of the DEP chip consists of a top electrode made of indium tin oxide (ITO), a flow chamber formed by optically clear adhesive (OCA) tape and bottom electrodes with different patterns for different purposes. The bottom electrodes can be divided into three parts: a fish-bone type electrode array which provides the positive DEP force for focusing the suspended nanoparticles near the inlet in the flow chamber; the second is for switching and guiding the focused nanoparticles along the electrode surface to the target area, like a flow passing along a virtual channel; and a trapping electrode in the downstream for trapping and releasing the guided nanoparticles. According to the simulation and experimental results, nanoparticles can be aligned along the electrode of the focusing electrode and guided toward the target electrode by means of a positive DEP force between the top and bottom electrodes, with the effects of Brownian motion and Stokes force. In order to demonstrate the sequence of DEP manipulations, a PMMA-NP suspension is introduced to the DEP chip; the size of the PMMA-SMPs is about 300 nm. Furthermore, a LabVIEW program developed for sequence control of the AC signals for the multi-step manipulations. Consequently, the DEP chip provides an excellent platform technology for the multi-step manipulation of submicron particles.