Electrophoretic versus dielectrophoretic nanoparticle patterning using optoelectronic tweezers

Abstract

Currently, there is increasing interest from many scientific disciplines in the development of systems that are able to sort and arrange many objects in parallel at the nano-and micrometric scale. Among others, photovoltaic tweezers (PVT) are an optoelectronic technique for trapping and patterning nano-and micro-objects in accordance with an arbitrary light profile. In this work, the differential features of electro-and dielectrophoretic (EP and DEP) nanoparticle (NP) patterning using PVT are deeply investigated. The study is carried out through theory and experiments. The developed theory extends the applicability of a previously reported model to be able to compute EP potentials and to obtain numerical values for the EP and DEP potential energies. Two-dimensional patterns of charged and neutral aluminum NPs are fabricated on top of Fe:LiNbO3 crystals, and different light distributions and other experimental parameters (crystal thickness and NP concentration) are compared. Patterns of charged and neutral NPs show remarkable differences in both particle density distribution and fidelity to the original light profile. The observed different features between EP and DEP trapping are satisfactorily explained by the theoretical analysis. The results provide routes for the optimization of the NP arrangements for both regimes.