Dielectrophoretic concentration of low-abundance nanoparticles using a nanostructured tip

Electric field-induced concentration has the potential for application in highly sensitive detection of nanoparticles (NPs) for disease diagnosis and drug discovery. Conventional two-dimensional planar electrodes, however, have shown limited sensitivity in NP concentration. In this paper, the dielectrophoretic (DEP) concentration of low-abundance NPs is studied using a nanostructured tip where a high electric field of 3 × 10(7) V m(-1) is generated. In experimental studies, individual 2, 10, and 100 nm Au NPs are concentrated to a nanotip using DEP concentration and are detected by scanning transmission and scanning electron microscopes. The DEP force on Au NPs near the end of a nanotip is computed according to the distance, and then compared with Brownian motion-induced force. The computational study shows qualitative agreement with the experimental results. When the experimental conditions for DEP concentration are optimized for 8 nm-long oligonucleotides, the sensitivity of a nanotip is 10 aM (10 attomolar; nine copies in a 1.5 μl sample volume). This DEP concentrator using a nanotip can be used for molecular detection without amplification.