We demonstrate experimentally and numerically the use of nano-antennas to trap and manipulate gold nano-particles of sub-wavelength sizes by subjecting them to dielectrophoresis. The trapping was realized by illuminating arrays of nano-antennas with IR laser light. The trapping experiments were conducted alongside numerical simulations.

Directed assembly and precise manipulation of nano-particles onto specific locations is one of the major challenges in contemporary nano-technology. Here we propose and demonstrate a technique for manipulation and large scale trapping of nano-scale particles using dielectrophoresis (DEP) by illuminating nano-antenna arrays. DEP occurs when a dielectric particle, which is suspended in a fluid with different dielectric and conduction properties, is subjected to a spatially non-uniform electric field. In our experiments the trapping is achieved by illuminating nano-antennas at their resonance frequency, thereby generating a strong, highly non-uniform electric field. Due to the antenna structure, the field is focused to sub-wavelength zones where it is enhanced and promotes trapping at relatively low optical powers. Once a particle is trapped it causes a change in the spectral response of the antennas, allowing real-time, sensitive sensing of the trapping. In this presentation we discuss the numerical methods we used to design our antenna arrays and simulate the motion of particles subjected to the trapping force. In addition we present the trapping experiments which were performed with 50 nm gold nano-particles immersed in isopropanol and compare them to numerical predictions.

Our results demonstrate a change in the spectral response of the antennas which trapped particles. SEM inspection indicates that particles were attracted and trapped at the regions where the field gradient was high, and particle clustering is observed and investigated using numerical simulations.