Particle clustering during pearl chain formation in a conductive-island based dielectrophoretic assembly system

A dielectrophoretically (DEP) assembled metal nanoparticle chain can serve as an electrical connector between small conductive elements in wet electronics or as a sensing element for chemical and biological substances. Obviously, the morphology of the nanoparticle assembled chain has a strong influence on electrical conductance and surface area of this connector. This paper presents an experimental discovery that as a connection of the electrode pair to an initially isolated conductive island is formed by the assembled nanoparticle chain, an abundance of particle clusters can also be generated, which tend to accumulate on the edge of the conductive structures under certain conditions. These particle clusters either can have an undesirable impact on consistency in electrical conductance of the electric circuit or can be used to enhance the susceptibility of the sensors due to an increased surface area. Therefore, exploration is also made for manipulating and assembling metallic nanoparticles on the surface or edge of a conductive island by changing the AC frequency in the conductive island based DEP assembly system. In order to develop an explanation of the experimental observations, numerical simulation is performed to investigate the combined influence of DEP force and electrothermal flow on individual nanoparticles by taking account of the near-field effect due to particle-solid interaction or particle-particle interaction.