Ionic Current Detection of Nanoparticles Driven by an Optical Vortex

Optical tweezers have been a well-known non-contact technique for manipulation of micro- and nanoobjects in narrow spaces, since Ashkin was firstly reported theoretical and experimental studies of optical trapping. Optical forces acting on a small object are divided into the scattering force and gradient force, which effectively work to capture a particle in a fluid. In this study, we apply an optical vortex, which traps and drives a gold nanoparticle in a circular orbit, to improve the throughput and signal-to-noise ration of electrical measurements using a double nano-slit structure. An optically manipulated gold nanoparticle iteratively passes through the double nano-slit, and conductive pulses of ionic current responses are often observed. It is suspected that an ionic current condition is improved by the irradiated optical vortex as well as the volume exclusion effect.