Designing a Plasmonic Optophoresis System for Trapping and Simultaneous Sorting/Counting of Micro- and Nano-Particles

We are proposing a plasmonic-based optophoresis system that can trap and simultaneously sort and count metallic and dielectric micro- and nano-particles, in a simple microfluidic system. The operating principles of the proposed system are based on the particles intrinsic properties that modulate the induced optical force and the transmitted power. Particle manipulations, in this system, are based on the near-field optical forces exerted by leaky surface plasmons modes, excited on a gold stripe. Simulations show that the maximum potential depth sensitivity to the trapped PS/Au particles´ radius is ~0.09/0.03 (k_BT/nm). The maximum transmission sensitivity in response to a change in radii of trapped Au and PS spheres are both ~0.01% per nm. Moreover, it is also shown that a minute change of ±1% in a refractive index of a 250-nm trapped dielectric particle results in ±0.26 kB T and ∓0.13% variations in the potential depth and transmission, respectively. Furthermore, the proposed system that can be implemented simply and inexpensively, benefits from its small footprint for integration into lab-on-a-chip devices and low power consumption, with promising potentials for biological applications.