Photonic crystal (PhC) cavities have been widely utilized for the optical trapping. However, it is still challenging to achieve high-efficiency optical trapping of ultrasmall nanoparticles. In this paper, we show optical trapping of a 3 nm size single nanoparticle by using an ultrahigh Q/V bow-tie-shaped PhC nanobeam cavity. For the trapping of a single polystyrene nanoparticle with the radius as small as 3 nm, a maximum trapping force of 1.2 × 105 pN/mW is theoretically obtained, which is at least one order of magnitude higher than the previous results. Furthermore, the calculated sensitivity for the cavity is around 350 nm/RIU, which provides a valid solution for monitoring the trapping process of the nanoparticles with ultrasmall size. We believe that such structure with characteristics of extreme light confinement and high trapping efficiency will be conducive to the development of multifunctional on-chip trapping devices.
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