A 3D nanoelectrokinetic model for predictive assembly of nanowire arrays using floating electrode dielectrophoresis

Floating electrode dielectrophoresis (FE-DEP) presents a promising avenue for scalable assembly of nanowire (NW) arrays on silicon chips and offers better control in limiting the number of deposited NWs when compared with the conventional, two-electrode DEP process. This article presents a 3D nanoelectrokinetic model, which calculates the imposed electric field and its resultant NW force/velocity maps within the region of influence of an electrode array operating in the FE-DEP configuration. This enables the calculation of NW trajectories and their eventual localization sites on the target electrodes as a function of parameters such as NW starting position, NW size, the applied electric field, suspension concentration, and deposition time. The accuracy of this model has been established through a direct quantitative comparison with the assembly of manganese dioxide NW arrays. Further analysis of the computed data reveals interesting insights into the following aspects: (a) asymmetry in NW localization at electrode sites, and (b) the workspace regions from which NWs are drawn to assemble such that their center-of-mass is located either in the inter-electrode gap region (desired) or on top of one of the assembly electrodes (undesired). This analysis is leveraged to outline a strategy, which involves a physical confinement of the NW suspension within lithographically patterned reservoirs during assembly, for single NW deposition across large arrays with high estimated assembly yields on the order of 87%.